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• Are python list comprehensions always a good programming practice?

  - by dln385

  To make the question clear, I'll use a specific example. I have a list of college courses, and each course has a few fields (all of which are strings). The user gives me a string of search terms, and I return a list of courses that match all of the search terms. This can be done in a single list comprehension or a few nested for loops. Here's the implementation. First, the Course class: class Course: def __init__(self, date, title, instructor, ID, description, instructorDescription, *args): self.date = date self.title = title self.instructor = instructor self.ID = ID self.description = description self.instructorDescription = instructorDescription self.misc = args Every field is a string, except misc, which is a list of strings. Here's the search as a single list comprehension. courses is the list of courses, and query is the string of search terms, for example "history project". def searchCourses(courses, query): terms = query.lower().strip().split() return tuple(course for course in courses if all( term in course.date.lower() or term in course.title.lower() or term in course.instructor.lower() or term in course.ID.lower() or term in course.description.lower() or term in course.instructorDescription.lower() or any(term in item.lower() for item in course.misc) for term in terms)) You'll notice that a complex list comprehension is difficult to read. I implemented the same logic as nested for loops, and created this alternative: def searchCourses2(courses, query): terms = query.lower().strip().split() results = [] for course in courses: for term in terms: if (term in course.date.lower() or term in course.title.lower() or term in course.instructor.lower() or term in course.ID.lower() or term in course.description.lower() or term in course.instructorDescription.lower()): break for item in course.misc: if term in item.lower(): break else: continue break else: continue results.append(course) return tuple(results) That logic can be hard to follow too. I have verified that both methods return the correct results. Both methods are nearly equivalent in speed, except in some cases. I ran some tests with timeit, and found that the former is three times faster when the user searches for multiple uncommon terms, while the latter is three times faster when the user searches for multiple common terms. Still, this is not a big enough difference to make me worry. So my question is this: which is better? Are list comprehensions always the way to go, or should complicated statements be handled with nested for loops? Or is there a better solution altogether?

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• Friendly way to parse XDocument

  - by Oli

  I have a class that various different XML schemes are created from. I create the various dynamic XDocuments via one (Very long) statement using conditional operators for optional elements and attributes. I now need to convert the XDocuments back to the class but as they are coming from different schemes many elements and sub elements may be optional. The only way I know of doing this is to use a lot of if statements. This approach doesn't seem very LINQ and uses a great deal more code than when I create the XDocument so I wondered if there is a better way to do this? An example would be to get <?xml version="1.0"?> <root xmlns="somenamespace"> <object attribute1="This is Optional" attribute2="This is required"> <element1>Required</element1> <element1>Optional</element1> <List1> Optional List Of Elements </List1> <List2> Required List Of Elements </List2> </object> </root> Into public class Object() { public string Attribute1; public string Attribute2; public string Element1; public string Element2; public List<ListItem1> List1; public List<ListItem2> List2; } In a more LINQ friendly way than this: public bool ParseXDocument(string xml) { XNamespace xn = "somenamespace"; XDocument document = XDocument.Parse(xml); XElement elementRoot = description.Element(xn + "root"); if (elementRoot != null) { //Get Object Element XElement elementObject = elementRoot.Element(xn + "object"); if(elementObject != null) { if(elementObject.Attribute(xn + "attribute1") != null) { Attribute1 = elementObject.Attribute(xn + "attribute1"); } if(elementObject.Attribute(xn + "attribute2") != null) { Attribute2 = elementObject.Attribute(xn + "attribute2"); } else { //This is a required Attribute so return false return false; } //If, If/Elses get deeper and deeper for the next elements and lists etc.... } else { //Object is a required element so return false return false; } } else { //Root is a required element so return false return false; } return true; } Update: Just to clarify the ParseXDocument method is inside the "Object" class. Every time an xml document is received the Object class instance has some or all of it's values updated.

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• how can I create macro definitions for the lines commented in the code.

  - by yaprak

  #include <stdio.h> //Here use a macro definition that assigns a value to SIZE (for example 5) int main() { int i; int array[SIZE]; int sum=0; for(i=0; i<SIZE; i++) { //Here use a macro definition named as CALCSUM to make the //following addition operation for the array printf("Enter a[%d] = ",i); scanf("%d", &array[i]); sum+=array[i]; //Here use a macro definition named as VERBOSE to print //what program does to the screen printf("The user entered %d\n", array[i]); // // //If the macro definition CALCSUM is not used, the program //should assign 0 to the i-th element of the array array[i]=0; //Here, again use VERBOSE to print what program does to the screen printf("a[%d] is assigned to zero\n", i); // // } //If CALCSUM is defined, print the summation of the array elements to the screen printf("Summation of the array is %d\n",sum); // //If CALCSUM is not defined, but VERBOSE mode is used, print the following printf("All the elements in the array are assigned to zero\n"); // printf("Program terminated\n"); return 0; } When CALCSUM is defined, the program will sum up the values of each element in the given array. If CALCSUM is not defined, each array element will be assigned to zero. Besides, when VERBOSE mode is defined, the program will make print statements pointed out active. [root@linux55]# gcc code.c [root@linux55]# ./a.out Program terminated [root@linux55]# gcc code.c -D CALCSUM [root@linux55]# ./a.out Enter a[0] = 3 Enter a[1] = 0 Enter a[2] = 2 Enter a[3] = 5 Enter a[4] = 9 Summation of the array is 19 Program terminated [root@linux55]# gcc code.c -D CALCSUM -D VERBOSE [root@linux55]# ./a.out Enter a[0] = 2 The user entered 2 Enter a[1] = 10 The user entered 10 Enter a[2] = 3 The user entered 3 Enter a[3] = 8 The user entered 8 Enter a[4] = 1 The user entered 1 Summation of the array is 24 Program terminated [root@linux55]# gcc code.c -D VERBOSE [root@linux55]# ./a.out a[0] is assigned to 0 a[1] is assigned to 0 a[2] is assigned to 0 a[3] is assigned to 0 a[4] is assigned to 0 All the elements in the array is assigned to zero Program terminated

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• The big last_insert_id() problem, again.

  - by wretrOvian

  Note - this follows my question here: http://stackoverflow.com/questions/2983685/jdbc-does-the-connection-break-if-i-lose-reference-to-the-connection-object Now i have a created a class so i can deal with JDBC easily for the rest of my code - public class Functions { private String DB_SERVER = ""; private String DB_NAME = "test"; private String DB_USERNAME = "root"; private String DB_PASSWORD = "password"; public Connection con; public PreparedStatement ps; public ResultSet rs; public ResultSetMetaData rsmd; public void connect() throws java.io.FileNotFoundException, java.io.IOException, SQLException, Exception { String[] dbParms = Parameters.load(); DB_SERVER = dbParms[0]; DB_NAME = dbParms[1]; DB_USERNAME = dbParms[2]; DB_PASSWORD = dbParms[3]; // Connect. Class.forName("com.mysql.jdbc.Driver").newInstance(); con = DriverManager.getConnection("jdbc:mysql://" + DB_SERVER + "/" + DB_NAME, DB_USERNAME, DB_PASSWORD); } public void disconnect() throws SQLException { // Close. con.close(); } } As seen Parameters.load() refreshes the connection parameters from a file every-time, so that any changes to the same may be applied on the next immediate connection. An example of this class in action - public static void add(String NAME) throws java.io.FileNotFoundException, java.io.IOException, SQLException, Exception { Functions dbf = new Functions(); dbf.connect(); String query = "INSERT INTO " + TABLE_NAME + "(" + "NAME" + ") VALUES(?)"; PreparedStatement ps = dbf.con.prepareStatement(query); ps.setString(1, NAME); ps.executeUpdate(); dbf.disconnect(); } Now here is the problem - for adding a record to the table above, the add() method will open a connection, add the record - and then call disconnect() . What if i want to get the ID of the inserted record after i call add() -like this : Department.add("new dept"); int ID = getlastID(); Isn't it possible that another add() was called between those two statements?

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• Improving performance for WRITE operation on Oracle DB in Java

  - by Lucky

  I've a typical scenario & need to understand best possible way to handle this, so here it goes - I'm developing a solution that will retrieve data from a remote SOAP based web service & will then push this data to an Oracle database on network. Also, this will be a scheduled task that will execute every 15 minutes. I've event queues on remote service that contains the INSERT/UPDATE/DELETE operations that have been done since last retrieval, & once I retrieve the events for last 15 minutes, it again add events for next retrieval. Now, its just pushing data to Oracle so all my interactions are INSERT & UPDATE statements. There are around 60 tables on Oracle with some of them having 100+ columns. Moreover, for every 15 minutes cycle there would be around 60-70 Inserts, 100+ Updates & 10-20 Deletes. This will be an executable jar file that will terminate after operation & will again start on next 15 minutes cycle. So, I need to understand how should I handle WRITE operations (best practices) to improve performance for this application as whole ? Current Test Code (on every cycle) - Connects to remote service to get events. Creates a connection with DB (single connection object). Identifies the type of operation (INSERT/UPDATE/DELETE) & table on which it is done. After above, calls the respective method based on type of operation & table. Uses Preparedstatement with positional parameters, & retrieves each column value from remote service & assigns that to statement parameters. Commits the statement & returns to get event class to process next event. Above is repeated till all the retrieved events are processed after which program closes & then starts on next cycle & everything repeats again. Thanks for help !

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• Persistent static routes fail on MacOS 10.6.5 startup!

  - by verbalicious

  I'm unable to get static routes to persist a reboot on Mac OS 10.6.5. I've tried all of the methods prescribed in Google search results, and previous posts on this site. I've tried manually creating a launchd daemon, and used RouteSplit's launchd daemon to no avail. It's clear that the interface is not ready when these methods attempt to apply the route. This workstation in question is getting its IP from DHCP and probably hasn't gotten its DHCP lease when the command runs. We're able to apply the route by hand when logged in, but not through startup methods. Is there another way to apply this route by sneaking the command into something later, but before the login window appears to the user? Here is some relevant log info from system.log. You can see the "route: writing to routing socket: Network is unreachable" errors where my launchd script fires off. I've tried adding extra "sleep" and "ipconfig waitall" statements later in the script but this doesn't fly. Dec 15 19:30:41 localhost com.apple.launchd[1]: *** launchd[1] has started up. *** Dec 15 19:30:45 localhost mDNSResponder[18]: mDNSResponder mDNSResponder-258.13 (Oct 8 2010 17:10:30) starting Dec 15 19:30:47 localhost configd[15]: bootp_session_transmit: bpf_write(en1) failed: Network is down (50) Dec 15 19:30:47 localhost configd[15]: DHCP en1: INIT transmit failed Dec 15 19:30:47 localhost configd[15]: network configuration changed. Dec 15 19:30:47 Administrators-MacBook-Pro configd[15]: setting hostname to "Administrators-MacBook-Pro.local" Dec 15 19:30:47 Administrators-MacBook-Pro blued[16]: Apple Bluetooth daemon started Dec 15 19:30:52 Administrators-MacBook-Pro syslog[67]: routes.sh: Starting RouteSplit Dec 15 19:30:53 Administrators-MacBook-Pro com.apple.usbmuxd[41]: usbmuxd-207 built for iTunesTenOne on Oct 19 2010 at 13:50:35, running 64 bit Dec 15 19:30:54 Administrators-MacBook-Pro /System/Library/CoreServices/loginwindow.app/Contents/MacOS/loginwindow[50]: Login Window Application Started Dec 15 19:30:55 Administrators-MacBook-Pro bootlog[61]: BOOT_TIME: 1292459441 0 Dec 15 19:30:55 Administrators-MacBook-Pro syslog[86]: routes.sh: static route 192.168.0.0/23 192.168.2.2 Dec 15 19:30:55 Administrators-MacBook-Pro net.routes.static[65]: route: writing to routing socket: Network is unreachable Dec 15 19:30:55 Administrators-MacBook-Pro net.routes.static[65]: add net 192.168.0.0: gateway 192.168.2.2: Network is unreachable Dec 15 19:30:57 Administrators-MacBook-Pro org.apache.httpd[38]: httpd: Could not reliably determine the server's fully qualified domain name, using Administrators-MacBook-Pro.local for ServerName Dec 15 19:30:58 Administrators-MacBook-Pro loginwindow[50]: Login Window Started Security Agent Dec 15 19:30:58 Administrators-MacBook-Pro WindowServer[89]: kCGErrorFailure: Set a breakpoint @ CGErrorBreakpoint() to catch errors as they are logged. Dec 15 19:30:58 Administrators-MacBook-Pro com.apple.WindowServer[89]: Wed Dec 15 19:30:58 Administrators-MacBook-Pro.local WindowServer[89] <Error>: kCGErrorFailure: Set a breakpoint @ CGErrorBreakpoint() to catch errors as they are logged. Dec 15 19:31:18 Administrators-MacBook-Pro configd[15]: network configuration changed. Dec 15 19:31:19 administrators-macbook-pro configd[15]: setting hostname to "administrators-macbook-pro.local" Dec 15 19:31:25 administrators-macbook-pro _mdnsresponder[121]: /usr/libexec/ntpd-wrapper: scutil key State:/Network/Global/DNS not present after 30 seconds Dec 15 19:31:25 administrators-macbook-pro _mdnsresponder[124]: sntp options: a=2 v=1 e=0.100 E=5.000 P=2147483647.000 Dec 15 19:31:25 administrators-macbook-pro _mdnsresponder[124]: d=15 c=5 x=0 op=1 l=/var/run/sntp.pid f= time.apple.com Dec 15 19:31:25 administrators-macbook-pro _mdnsresponder[124]: sntp: getaddrinfo(hostname, ntp) failed with nodename nor servname provided, or not known Dec 15 19:31:27 administrators-macbook-pro configd[15]: network configuration changed. Dec 15 19:31:27 Administrators-MacBook-Pro configd[15]: setting hostname to "Administrators-MacBook-Pro.local" Dec 15 19:31:27 Administrators-MacBook-Pro ntpd[37]: Cannot find existing interface for address 17.151.16.20 Dec 15 19:31:27 Administrators-MacBook-Pro ntpd_initres[125]: ntpd indicates no data available! Dec 15 19:31:31 Administrators-MacBook-Pro sshd[128]: USER_PROCESS: 133 ttys000 Dec 15 19:31:37 Administrators-MacBook-Pro sudo[138]: administrator : TTY=ttys000 ; PWD=/Users/administrator ; USER=root ; COMMAND=/usr/bin/less /var/log/system.log ``You can see the following line in /var/log/kernel.log that shows the en0 interface coming up: Dec 15 19:30:51 Administrators-MacBook-Pro kernel[0]: Ethernet [AppleBCM5701Ethernet]: Link up on en0, 1-Gigabit, Full-duplex, No flow-control, Debug [796d,0f01,0de1,0300,c1e1,3800]

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• How do I create a Linked Server in SQL Server 2005 to a password protected Access 95 database?

  - by Brad Knowles

  I need to create a linked server with SQL Server Management Studio 2005 to an Access 95 database, which happens to be password protected at the database level. User level security has not been implemented. I cannot convert the Access database to a newer version. It is being used by a 3rd party application; so modifying it, in any way, is not allowed. I've tried using the Jet 4.0 OLE DB Provider and the ODBC OLE DB Provider. The 3rd party application creates a System DSN (with the proper database password), but I've not had any luck in using either method. If I were using a standard connection string, I think it would look something like this: Provider=Microsoft.Jet.OLEDB.4.0;Data Source='C:\Test.mdb';Jet OLEDB:Database Password=####; I'm fairly certain I need to somehow incorporate Jet OLEDB:Database Password into the linked server setup, but haven't figured out how. I've posted the scripts I'm using along with the associated error messages below. Any help is greatly appreciated. I'll provide more details if needed, just ask. Thanks! Method #1 - Using the Jet 4.0 Provider When I try to run these statements to create the linked server: sp_dropserver 'Test', 'droplogins'; EXEC sp_addlinkedserver @server = N'Test', @provider = N'Microsoft.Jet.OLEDB.4.0', @srvproduct = N'Access DB', @datasrc = N'C:\Test.mdb' GO EXEC sp_addlinkedsrvlogin @rmtsrvname=N'Test', @useself=N'False',@locallogin=NULL, @rmtuser=N'Admin', @rmtpassword='####' GO I get this error when testing the connection: TITLE: Microsoft SQL Server Management Studio ------------------------------ "The test connection to the linked server failed." ------------------------------ ADDITIONAL INFORMATION: An exception occurred while executing a Transact-SQL statement or batch. (Microsoft.SqlServer.ConnectionInfo) ------------------------------ The OLE DB provider "Microsoft.Jet.OLEDB.4.0" for linked server "Test" reported an error. Authentication failed. Cannot initialize the data source object of OLE DB provider "Microsoft.Jet.OLEDB.4.0" for linked server "Test". OLE DB provider "Microsoft.Jet.OLEDB.4.0" for linked server "Test" returned message "Cannot start your application. The workgroup information file is missing or opened exclusively by another user.". (Microsoft SQL Server, Error: 7399) ------------------------------ Method #2 - Using the ODBC Provider... sp_dropserver 'Test', 'droplogins'; EXEC sp_addlinkedserver @server = N'Test', @provider = N'MSDASQL', @srvproduct = N'ODBC', @datasrc = N'Test:DSN' GO EXEC sp_addlinkedsrvlogin @rmtsrvname=N'Test', @useself=N'False',@locallogin=NULL, @rmtuser=N'Admin', @rmtpassword='####' GO I get this error: TITLE: Microsoft SQL Server Management Studio ------------------------------ "The test connection to the linked server failed." ------------------------------ ADDITIONAL INFORMATION: An exception occurred while executing a Transact-SQL statement or batch. (Microsoft.SqlServer.ConnectionInfo) ------------------------------ Cannot initialize the data source object of OLE DB provider "MSDASQL" for linked server "Test". OLE DB provider "MSDASQL" for linked server "Test" returned message "[Microsoft][ODBC Driver Manager] Driver's SQLSetConnectAttr failed". OLE DB provider "MSDASQL" for linked server "Test" returned message "[Microsoft][ODBC Driver Manager] Driver's SQLSetConnectAttr failed". OLE DB provider "MSDASQL" for linked server "Test" returned message "[Microsoft][ODBC Microsoft Access Driver] Cannot open database '(unknown)'. It may not be a database that your application recognizes, or the file may be corrupt.". (Microsoft SQL Server, Error: 7303)

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• Persistent static routes fail on MacOS 10.6.5 startup!

  - by verbalicious

  I'm unable to get static routes to persist a reboot on Mac OS 10.6.5. I've tried all of the methods prescribed in Google search results, and previous posts on this site. I've tried manually creating a launchd daemon, and used RouteSplit's launchd daemon to no avail. It's clear that the interface is not ready when these methods attempt to apply the route. This workstation in question is getting its IP from DHCP and probably hasn't gotten its DHCP lease when the command runs. We're able to apply the route by hand when logged in, but not through startup methods. Is there another way to apply this route by sneaking the command into something later, but before the login window appears to the user? Here is some relevant log info from system.log. You can see the "route: writing to routing socket: Network is unreachable" errors where my launchd script fires off. I've tried adding extra "sleep" and "ipconfig waitall" statements later in the script but this doesn't fly. Dec 15 19:30:41 localhost com.apple.launchd[1]: *** launchd[1] has started up. *** Dec 15 19:30:45 localhost mDNSResponder[18]: mDNSResponder mDNSResponder-258.13 (Oct 8 2010 17:10:30) starting Dec 15 19:30:47 localhost configd[15]: bootp_session_transmit: bpf_write(en1) failed: Network is down (50) Dec 15 19:30:47 localhost configd[15]: DHCP en1: INIT transmit failed Dec 15 19:30:47 localhost configd[15]: network configuration changed. Dec 15 19:30:47 Administrators-MacBook-Pro configd[15]: setting hostname to "Administrators-MacBook-Pro.local" Dec 15 19:30:47 Administrators-MacBook-Pro blued[16]: Apple Bluetooth daemon started Dec 15 19:30:52 Administrators-MacBook-Pro syslog[67]: routes.sh: Starting RouteSplit Dec 15 19:30:53 Administrators-MacBook-Pro com.apple.usbmuxd[41]: usbmuxd-207 built for iTunesTenOne on Oct 19 2010 at 13:50:35, running 64 bit Dec 15 19:30:54 Administrators-MacBook-Pro /System/Library/CoreServices/loginwindow.app/Contents/MacOS/loginwindow[50]: Login Window Application Started Dec 15 19:30:55 Administrators-MacBook-Pro bootlog[61]: BOOT_TIME: 1292459441 0 Dec 15 19:30:55 Administrators-MacBook-Pro syslog[86]: routes.sh: static route 192.168.0.0/23 192.168.2.2 Dec 15 19:30:55 Administrators-MacBook-Pro net.routes.static[65]: route: writing to routing socket: Network is unreachable Dec 15 19:30:55 Administrators-MacBook-Pro net.routes.static[65]: add net 192.168.0.0: gateway 192.168.2.2: Network is unreachable Dec 15 19:30:57 Administrators-MacBook-Pro org.apache.httpd[38]: httpd: Could not reliably determine the server's fully qualified domain name, using Administrators-MacBook-Pro.local for ServerName Dec 15 19:30:58 Administrators-MacBook-Pro loginwindow[50]: Login Window Started Security Agent Dec 15 19:30:58 Administrators-MacBook-Pro WindowServer[89]: kCGErrorFailure: Set a breakpoint @ CGErrorBreakpoint() to catch errors as they are logged. Dec 15 19:30:58 Administrators-MacBook-Pro com.apple.WindowServer[89]: Wed Dec 15 19:30:58 Administrators-MacBook-Pro.local WindowServer[89] <Error>: kCGErrorFailure: Set a breakpoint @ CGErrorBreakpoint() to catch errors as they are logged. Dec 15 19:31:18 Administrators-MacBook-Pro configd[15]: network configuration changed. Dec 15 19:31:19 administrators-macbook-pro configd[15]: setting hostname to "administrators-macbook-pro.local" Dec 15 19:31:25 administrators-macbook-pro _mdnsresponder[121]: /usr/libexec/ntpd-wrapper: scutil key State:/Network/Global/DNS not present after 30 seconds Dec 15 19:31:25 administrators-macbook-pro _mdnsresponder[124]: sntp options: a=2 v=1 e=0.100 E=5.000 P=2147483647.000 Dec 15 19:31:25 administrators-macbook-pro _mdnsresponder[124]: d=15 c=5 x=0 op=1 l=/var/run/sntp.pid f= time.apple.com Dec 15 19:31:25 administrators-macbook-pro _mdnsresponder[124]: sntp: getaddrinfo(hostname, ntp) failed with nodename nor servname provided, or not known Dec 15 19:31:27 administrators-macbook-pro configd[15]: network configuration changed. Dec 15 19:31:27 Administrators-MacBook-Pro configd[15]: setting hostname to "Administrators-MacBook-Pro.local" Dec 15 19:31:27 Administrators-MacBook-Pro ntpd[37]: Cannot find existing interface for address 17.151.16.20 Dec 15 19:31:27 Administrators-MacBook-Pro ntpd_initres[125]: ntpd indicates no data available! Dec 15 19:31:31 Administrators-MacBook-Pro sshd[128]: USER_PROCESS: 133 ttys000 Dec 15 19:31:37 Administrators-MacBook-Pro sudo[138]: administrator : TTY=ttys000 ; PWD=/Users/administrator ; USER=root ; COMMAND=/usr/bin/less /var/log/system.log ``You can see the following line in /var/log/kernel.log that shows the en0 interface coming up: Dec 15 19:30:51 Administrators-MacBook-Pro kernel[0]: Ethernet [AppleBCM5701Ethernet]: Link up on en0, 1-Gigabit, Full-duplex, No flow-control, Debug [796d,0f01,0de1,0300,c1e1,3800]

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• What are the pitfalls of hardlinked files on my desktop PC?

  - by MountainX

  All the identical-content files on my PC are now hardlinked. (My data is completely de-duplicated. It is a consequence of the way I copied my data from my old computer.) What pitfalls do I need to be aware of now that certain actions on one file could silently affect a number of other files? I know that deleting the file I'm working on is not a problem (assuming I deleted it on purpose). It doesn't affect any of the other hardlinked files and I don't see that the delete action would lead to unexpected side effects. Moving or renaming the file is not a problem. I don't see any unexpected consequences. I don't think copying hardlinked files is a problem, but I'm not as confident about any unexpected consequences in this regard. What I have seen is that making a copy (to the same disk) of a hardlinked file with cp keeps the copy hardlinked (i.e., inode number doesn't change in the copy). Copying to another filesystem obviously breaks the hardlink. (I guess one pitfall is forgetting this fact, given that my PC has 3 hard disks.) Changing permissions does affect all linked files. So far this has proven handy. (I made a large number of the hardlinked files read-only.) None of the operations above seem to produce any major unexpected consequences. However, as was pointed out to me by Daniel Beck in a comment, editing or modifying a file can sometimes be a problem. It depends on the tool and maybe the type of edit. (For example, editing small text files using sed seems to always break the link while using nano doesn't.) This introduces the chance that editing one file could affect all the hardlinked files (i.e., alter the original inode). My proposed solution to this is to make all hardlinked files read-only (and that is already mostly the case). If I can't do that for some files, I will unlink those particular files. Is there any problem with this read-only approach? I'm assuming that if I go to edit a file and find it to be read-only, I'll remember to unlink that filename while making it writable. So one pitfall might be forgetting this rule. In that case, I'll have to rely on my backups. Am I correct in the above statements? And what else do I need to know? BTW, I'm running Kubuntu 12.04. I'm also using btrfs. (I have 2 SSD's and 1 HDD in the PC. I will also be adding an external USB HDD. I'm also connected to a network and I mount some NFS shares. I don't assume any of these last bits are relevant to the question, but I'm adding them just in case.) BTW, since I have more than one drive (with separate file systems), to unlink any file all I have to do is copy it to another drive, then move it back. However, using sed also works (in my testing). Here's my script: sed -i 's/\(.\)/\1/' file1 Surprisingly, this even unlinks zero byte files. In my testing it also appears to work on non-text files without any special options. (But I understand that the --binary option might be needed on Windows, MS-DOS and Cygwin.) However, copying to another disk and moving back may be the best way to unlink. For my use-case, unlink command doesn't really "unlink", rather it "removes".

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• Network authentication + roaming home directory - which technology should I look into using?

  - by Brian

  I'm looking into software which provides a user with a single identity across multiple computers. That is, a user should have the same permissions on each computer, and the user should have access to all of his or her files (roaming home directory) on each computer. There seem to be many solutions for this general idea, but I'm trying to determine the best one for me. Here are some details along with requirements: The network of machines are Amazon EC2 instances running Ubuntu. We access the machines with SSH. Some machines on this LAN may have different uses, but I am only discussing machines for a certain use (running a multi-tenancy platform). The system will not necessarily have a constant amount of machines. We may have to permanently or temporarily alter the amount of machines running. This is the the reason why I'm looking into centralized authentication/storage. The implementation of this effect should be a secure one. We're unsure if users will have direct shell access, but their software will potentially be running (under restricted Linux user names, of course) on our systems, which is as good as direct shell access. Let's assume that their software could potentially be malicious for the sake of security. I have heard of several technologies/combinations to achieve my goal, but I'm unsure of the ramifications of each. An older ServerFault post recommended NFS & NIS, though the combination has security problems according to this old article by Symantec. The article suggests moving to NIS+, but, as it is old, this Wikipedia article has cited statements suggesting a trending away from NIS+ by Sun. The recommended replacement is another thing I have heard of... LDAP. It looks like LDAP can be used to save user information in a centralized location on a network. NFS would still need to be used to cover the 'roaming home folder' requirement, but I see references of them being used together. Since the Symantec article pointed out security problems in both NIS and NFS, is there software to replace NFS, or should I heed that article's suggestions for locking it down? I'm tending toward LDAP because another fundamental piece of our architecture, RabbitMQ, has a authentication/authorization plugin for LDAP. RabbitMQ will be accessible in a restricted manner to users on the system, so I would like to tie the security systems together if possible. Kerberos is another secure authentication protocol that I have heard of. I learned a bit about it some years ago in a cryptography class but don't remember much about it. I have seen suggestions online that it can be combined with LDAP in several ways. Is this necessary? What are the security risks of LDAP without Kerberos? I also remember Kerberos being used in another piece of software developed by Carnegie Mellon University... Andrew File System, or AFS. OpenAFS is available for use, though its setup seems a bit complicated. At my university, AFS provides both requirements... I can log in to any machine, and my "AFS folder" is always available (at least when I acquire an AFS token). Along with suggestions for which path I should look into, does anybody have any guides which were particularly helpful? As the bold text pointed out, LDAP looks to be the best choice, but I'm particularly interested in the implementation details (Keberos? NFS?) with respect to security.

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• How to deploy custom MBean to Tomcat?

  - by Christian

  Hi, I'm trying to deploy a custom mbean to a tomcat. This mbean is not part of a webapp. It should be instantiated when tomcat starts. My problem is, I can't find any complete documentation about how to deploy such a mbean. I'm getting different exceptions, depending on my configuration. Has anyone hints, a complete documentation or has implemented a mbean by himself and can post an example? I configured tomcat to read a configuration from his conf directory: <Engine name="Catalina" defaultHost="localhost" mbeansFile="${catalina.base}/conf/mbeans-descriptors.xml"> The content is as follows: <?xml version="1.0"?> <!-- <!DOCTYPE mbeans-descriptors PUBLIC "-//Apache Software Foundation//DTD Model MBeans Configuration File" "http://jakarta.apache.org/commons/dtds/mbeans-descriptors.dtd"> --> <!-- Descriptions of JMX MBeans --> <mbeans-descriptors> <mbean name="Performance" description="Caculate JVM throughput" type="Performance"> <attribute name="throughput" description="calculated throughput (ratio between gc times and uptime of JVM)" type="double" writeable="false"/> </mbean> </mbeans-descriptors> When name in the xml file and class name match, I get this excption: SEVERE: Error creating mbean Performance javax.management.MalformedObjectNameException: Key properties cannot be empty at javax.management.ObjectName.construct(ObjectName.java:467) at javax.management.ObjectName.<init>(ObjectName.java:1403) at org.apache.tomcat.util.modeler.modules.MbeansSource.execute(MbeansSource.java:202) at org.apache.tomcat.util.modeler.modules.MbeansSource.load(MbeansSource.java:137) at org.apache.catalina.core.StandardEngine.readEngineMbeans(StandardEngine.java:517) at org.apache.catalina.core.StandardEngine.init(StandardEngine.java:321) at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:411) at org.apache.catalina.core.StandardService.start(StandardService.java:519) at org.apache.catalina.core.StandardServer.start(StandardServer.java:710) at org.apache.catalina.startup.Catalina.start(Catalina.java:581) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:289) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.apache.commons.daemon.support.DaemonLoader.start(DaemonLoader.java:177) When changing the name attribute in the xml file to test.example:type=Performance, I get this exception: SEVERE: Error creating mbean test.example:type=Performance javax.management.NotCompliantMBeanException: MBean class must have public constructor at com.sun.jmx.mbeanserver.Introspector.testCreation(Introspector.java:127) at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.createMBean(DefaultMBeanServerInterceptor.java:284) at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.createMBean(DefaultMBeanServerInterceptor.java:199) at com.sun.jmx.mbeanserver.JmxMBeanServer.createMBean(JmxMBeanServer.java:393) at org.apache.tomcat.util.modeler.modules.MbeansSource.execute(MbeansSource.java:207) at org.apache.tomcat.util.modeler.modules.MbeansSource.load(MbeansSource.java:137) at org.apache.catalina.core.StandardEngine.readEngineMbeans(StandardEngine.java:517) at org.apache.catalina.core.StandardEngine.init(StandardEngine.java:321) at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:411) at org.apache.catalina.core.StandardService.start(StandardService.java:519) at org.apache.catalina.core.StandardServer.start(StandardServer.java:710) at org.apache.catalina.startup.Catalina.start(Catalina.java:581) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:289) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.apache.commons.daemon.support.DaemonLoader.start(DaemonLoader.java:177) The documentation from apache is not really helpful, as it just explains a small part. I'm aware of this question but it doesn't help me. The answer I gave worked just for a short time, after that I got some other exceptions. For additional info, the java interface public interface PerformanceMBean { public double getThroughput(); } and implementing class /* some import statements */ public class Performance implements PerformanceMBean { public double getThroughput() { ... } }

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• Persistent static routes fail on MacOS 10.6.5 startup!

  - by verbalicious

  I'm unable to get static routes to persist a reboot on Mac OS 10.6.5. I've tried all of the methods prescribed in Google search results, and previous posts on this site. I've tried manually creating a launchd daemon, and used RouteSplit's launchd daemon to no avail. It's clear that the interface is not ready when these methods attempt to apply the route. This workstation in question is getting its IP from DHCP and probably hasn't gotten its DHCP lease when the command runs. We're able to apply the route by hand when logged in, but not through startup methods. Is there another way to apply this route by sneaking the command into something later, but before the login window appears to the user? Here is some relevant log info from system.log. You can see the "route: writing to routing socket: Network is unreachable" errors where my launchd script fires off. I've tried adding extra "sleep" and "ipconfig waitall" statements later in the script but this doesn't fly. Dec 15 19:30:41 localhost com.apple.launchd[1]: *** launchd[1] has started up. *** Dec 15 19:30:45 localhost mDNSResponder[18]: mDNSResponder mDNSResponder-258.13 (Oct 8 2010 17:10:30) starting Dec 15 19:30:47 localhost configd[15]: bootp_session_transmit: bpf_write(en1) failed: Network is down (50) Dec 15 19:30:47 localhost configd[15]: DHCP en1: INIT transmit failed Dec 15 19:30:47 localhost configd[15]: network configuration changed. Dec 15 19:30:47 Administrators-MacBook-Pro configd[15]: setting hostname to "Administrators-MacBook-Pro.local" Dec 15 19:30:47 Administrators-MacBook-Pro blued[16]: Apple Bluetooth daemon started Dec 15 19:30:52 Administrators-MacBook-Pro syslog[67]: routes.sh: Starting RouteSplit Dec 15 19:30:53 Administrators-MacBook-Pro com.apple.usbmuxd[41]: usbmuxd-207 built for iTunesTenOne on Oct 19 2010 at 13:50:35, running 64 bit Dec 15 19:30:54 Administrators-MacBook-Pro /System/Library/CoreServices/loginwindow.app/Contents/MacOS/loginwindow[50]: Login Window Application Started Dec 15 19:30:55 Administrators-MacBook-Pro bootlog[61]: BOOT_TIME: 1292459441 0 Dec 15 19:30:55 Administrators-MacBook-Pro syslog[86]: routes.sh: static route 192.168.0.0/23 192.168.2.2 Dec 15 19:30:55 Administrators-MacBook-Pro net.routes.static[65]: route: writing to routing socket: Network is unreachable Dec 15 19:30:55 Administrators-MacBook-Pro net.routes.static[65]: add net 192.168.0.0: gateway 192.168.2.2: Network is unreachable Dec 15 19:30:57 Administrators-MacBook-Pro org.apache.httpd[38]: httpd: Could not reliably determine the server's fully qualified domain name, using Administrators-MacBook-Pro.local for ServerName Dec 15 19:30:58 Administrators-MacBook-Pro loginwindow[50]: Login Window Started Security Agent Dec 15 19:30:58 Administrators-MacBook-Pro WindowServer[89]: kCGErrorFailure: Set a breakpoint @ CGErrorBreakpoint() to catch errors as they are logged. Dec 15 19:30:58 Administrators-MacBook-Pro com.apple.WindowServer[89]: Wed Dec 15 19:30:58 Administrators-MacBook-Pro.local WindowServer[89] <Error>: kCGErrorFailure: Set a breakpoint @ CGErrorBreakpoint() to catch errors as they are logged. Dec 15 19:31:18 Administrators-MacBook-Pro configd[15]: network configuration changed. Dec 15 19:31:19 administrators-macbook-pro configd[15]: setting hostname to "administrators-macbook-pro.local" Dec 15 19:31:25 administrators-macbook-pro _mdnsresponder[121]: /usr/libexec/ntpd-wrapper: scutil key State:/Network/Global/DNS not present after 30 seconds Dec 15 19:31:25 administrators-macbook-pro _mdnsresponder[124]: sntp options: a=2 v=1 e=0.100 E=5.000 P=2147483647.000 Dec 15 19:31:25 administrators-macbook-pro _mdnsresponder[124]: d=15 c=5 x=0 op=1 l=/var/run/sntp.pid f= time.apple.com Dec 15 19:31:25 administrators-macbook-pro _mdnsresponder[124]: sntp: getaddrinfo(hostname, ntp) failed with nodename nor servname provided, or not known Dec 15 19:31:27 administrators-macbook-pro configd[15]: network configuration changed. Dec 15 19:31:27 Administrators-MacBook-Pro configd[15]: setting hostname to "Administrators-MacBook-Pro.local" Dec 15 19:31:27 Administrators-MacBook-Pro ntpd[37]: Cannot find existing interface for address 17.151.16.20 Dec 15 19:31:27 Administrators-MacBook-Pro ntpd_initres[125]: ntpd indicates no data available! Dec 15 19:31:31 Administrators-MacBook-Pro sshd[128]: USER_PROCESS: 133 ttys000 Dec 15 19:31:37 Administrators-MacBook-Pro sudo[138]: administrator : TTY=ttys000 ; PWD=/Users/administrator ; USER=root ; COMMAND=/usr/bin/less /var/log/system.log ``You can see the following line in /var/log/kernel.log that shows the en0 interface coming up: Dec 15 19:30:51 Administrators-MacBook-Pro kernel[0]: Ethernet [AppleBCM5701Ethernet]: Link up on en0, 1-Gigabit, Full-duplex, No flow-control, Debug [796d,0f01,0de1,0300,c1e1,3800]

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• How to export computers from Active Directory to XML using Powershell?

  - by CoDeRs

  I am trying to create a powershell scripts for Remote Desktop Connection Manager using the active directory module. My first thought was get a list of computers in AD and parse them out into XML format similar to the OU structure that is in AD. I have no problem with that, the below code will work just but not how I wanted. EG # here is a the array $OUs Americas/Canada/Canada Computers/Desktops Americas/Canada/Canada Computers/Laptops Americas/Canada/Canada Computers/Virtual Computers Americas/USA/USA Computers/Laptops Computers Disabled Accounts Domain Controllers EMEA/UK/UK Computers/Desktops EMEA/UK/UK Computers/Laptops Outside Sales and Service/Laptops Servers I wanted to have the basic XML structured like this Americas Canada Canada Computers Desktops Laptops Virtual Computers USA USA Computers Laptops Computers Disabled Accounts Domain Controllers EMEA UK UK Computers Desktops Laptops Outside Sales and Service Laptops Servers However if you run the below it does not nest the next string in the array it only restarts the from the beginning and duplicating Americas Canada Canada Computers Desktops Americas Canada Canada Computers Laptops Americas Canada Canada Computers Virtual Computers Americas USA USA Computers Laptops RDCMGenerator.ps1 #Importing Microsoft`s PowerShell-module for administering ActiveDirectory Import-Module ActiveDirectory #Initial variables $OUs = @() $RDCMVer = "2.2" $userName = "domain\username" $password = "Hashed Password+" $Path = "$env:temp\test.xml" $allComputers = Get-ADComputer -LDAPFilter "(OperatingSystem=*)" -Properties Name,Description,CanonicalName | Sort-Object CanonicalName | select Name,Description,CanonicalName $allOUObjects = $allComputers | Foreach {"$($_.CanonicalName)"} Function Initialize-XML{ ##<RDCMan schemaVersion="1"> $xmlWriter.WriteStartElement('RDCMan') $XmlWriter.WriteAttributeString('schemaVersion', '1') $xmlWriter.WriteElementString('version',$RDCMVer) $xmlWriter.WriteStartElement('file') $xmlWriter.WriteStartElement('properties') $xmlWriter.WriteElementString('name',$env:userdomain) $xmlWriter.WriteElementString('expanded','true') $xmlWriter.WriteElementString('comment','') $xmlWriter.WriteStartElement('logonCredentials') $XmlWriter.WriteAttributeString('inherit', 'None') $xmlWriter.WriteElementString('userName',$userName) $xmlWriter.WriteElementString('domain',$env:userdomain) $xmlWriter.WriteStartElement('password') $XmlWriter.WriteAttributeString('storeAsClearText', 'false') $XmlWriter.WriteRaw($password) $xmlWriter.WriteEndElement() $xmlWriter.WriteEndElement() $xmlWriter.WriteStartElement('connectionSettings') $XmlWriter.WriteAttributeString('inherit', 'FromParent') $xmlWriter.WriteEndElement() $xmlWriter.WriteStartElement('gatewaySettings') $XmlWriter.WriteAttributeString('inherit', 'FromParent') $xmlWriter.WriteEndElement() $xmlWriter.WriteStartElement('remoteDesktop') $XmlWriter.WriteAttributeString('inherit', 'None') $xmlWriter.WriteElementString('size','1024 x 768') $xmlWriter.WriteElementString('sameSizeAsClientArea','True') $xmlWriter.WriteElementString('fullScreen','False') $xmlWriter.WriteElementString('colorDepth','32') $xmlWriter.WriteEndElement() $xmlWriter.WriteStartElement('localResources') $XmlWriter.WriteAttributeString('inherit', 'FromParent') $xmlWriter.WriteEndElement() $xmlWriter.WriteStartElement('securitySettings') $XmlWriter.WriteAttributeString('inherit', 'FromParent') $xmlWriter.WriteEndElement() $xmlWriter.WriteStartElement('displaySettings') $XmlWriter.WriteAttributeString('inherit', 'FromParent') $xmlWriter.WriteEndElement() $xmlWriter.WriteEndElement() } Function Create-Group ($groupName){ #Start Group $xmlWriter.WriteStartElement('properties') $xmlWriter.WriteElementString('name',$groupName) $xmlWriter.WriteElementString('expanded','true') $xmlWriter.WriteElementString('comment','') $xmlWriter.WriteStartElement('logonCredentials') $XmlWriter.WriteAttributeString('inherit', 'FromParent') $xmlWriter.WriteEndElement() $xmlWriter.WriteStartElement('connectionSettings') $XmlWriter.WriteAttributeString('inherit', 'FromParent') $xmlWriter.WriteEndElement() $xmlWriter.WriteStartElement('gatewaySettings') $XmlWriter.WriteAttributeString('inherit', 'FromParent') $xmlWriter.WriteEndElement() $xmlWriter.WriteStartElement('remoteDesktop') $XmlWriter.WriteAttributeString('inherit', 'FromParent') $xmlWriter.WriteEndElement() $xmlWriter.WriteStartElement('localResources') $XmlWriter.WriteAttributeString('inherit', 'FromParent') $xmlWriter.WriteEndElement() $xmlWriter.WriteStartElement('securitySettings') $XmlWriter.WriteAttributeString('inherit', 'FromParent') $xmlWriter.WriteEndElement() $xmlWriter.WriteStartElement('displaySettings') $XmlWriter.WriteAttributeString('inherit', 'FromParent') $xmlWriter.WriteEndElement() $xmlWriter.WriteEndElement() } Function Create-Server ($computerName, $computerDescription) { #Start Server $xmlWriter.WriteStartElement('server') $xmlWriter.WriteElementString('name',$computerName) $xmlWriter.WriteElementString('displayName',$computerDescription) $xmlWriter.WriteElementString('comment','') $xmlWriter.WriteStartElement('logonCredentials') $XmlWriter.WriteAttributeString('inherit', 'FromParent') $xmlWriter.WriteEndElement() $xmlWriter.WriteStartElement('connectionSettings') $XmlWriter.WriteAttributeString('inherit', 'FromParent') $xmlWriter.WriteEndElement() $xmlWriter.WriteStartElement('gatewaySettings') $XmlWriter.WriteAttributeString('inherit', 'FromParent') $xmlWriter.WriteEndElement() $xmlWriter.WriteStartElement('remoteDesktop') $XmlWriter.WriteAttributeString('inherit', 'FromParent') $xmlWriter.WriteEndElement() $xmlWriter.WriteStartElement('localResources') $XmlWriter.WriteAttributeString('inherit', 'FromParent') $xmlWriter.WriteEndElement() $xmlWriter.WriteStartElement('securitySettings') $XmlWriter.WriteAttributeString('inherit', 'FromParent') $xmlWriter.WriteEndElement() $xmlWriter.WriteStartElement('displaySettings') $XmlWriter.WriteAttributeString('inherit', 'FromParent') $xmlWriter.WriteEndElement() $xmlWriter.WriteEndElement() #Stop Server } Function Close-XML { $xmlWriter.WriteEndElement() $xmlWriter.WriteEndElement() # finalize the document: $xmlWriter.Flush() $xmlWriter.Close() notepad $path } #Strip out Domain and Computer Name from CanonicalName foreach($OU in $allOUObjects){ $newSplit = $OU.split("/") $rebildOU = "" for($i=1; $i -le ($newSplit.count - 2); $i++){ $rebildOU += $newSplit[$i] + "/" } $OUs += $rebildOU.substring(0,($rebildOU.length - 1)) } #Remove Duplicate OU's $OUs = $OUs | select -uniq #$OUs # get an XMLTextWriter to create the XML $XmlWriter = New-Object System.XMl.XmlTextWriter($Path,$UTF8) # choose a pretty formatting: $xmlWriter.Formatting = 'Indented' $xmlWriter.Indentation = 1 $XmlWriter.IndentChar = "`t" # write the header $xmlWriter.WriteStartDocument() # # 'encoding', 'utf-8' How? # # set XSL statements #Initialize Pre-Defined XML Initialize-XML ######################################################### # Start Loop for each OU-Path that has a computer in it ######################################################### foreach ($OU in $OUs){ $totalGroupName = "" #Create / Reset Total OU-Path Completed $OU.split("/") | foreach { #Split the OU-Path into individual OU's $groupName = "$_" #Current OU $totalGroupName += $groupName + "/" #Total OU-Path Completed $xmlWriter.WriteStartElement('group') #Start new XML Group Create-Group $groupName #Call function to create XML Group ################################################ # Start Loop for each Computer in $allComputers ################################################ foreach($computer in $allComputers){ $computerOU = $computer.CanonicalName #Set the computers OU-Path $OUSplit = $computerOU.split("/") #Create the Split for the OU-Path $rebiltOU = "" #Create / Reset the stripped OU-Path for($i=1; $i -le ($OUSplit.count - 2); $i++){ #Start Loop for OU-Path to strip out the Domain and Computer Name $rebiltOU += $OUSplit[$i] + "/" #Rebuild the stripped OU-Path } if ($rebiltOU -eq $totalGroupName){ #Compare the Current OU-Path with the computers stripped OU-Path $computerName = $computer.Name #Set the computer name $computerDescription = $computerName + " - " + $computer.Description #Set the computer Description Create-Server $computerName $computerDescription #Call function to create XML Server } } } ################################################### # Start Loop to close out XML Groups created above ################################################### $totalGroupName.split("/") | foreach { #Split the if ($_ -ne "" ){ $xmlWriter.WriteEndElement() #End Group } } } Close-XML

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• FTP Upload works from local command line / remote GUI client but not from PHP script

  - by MrOodles

  I originally posted this question at StackOverflow, but I'm beginning to think it's more of a server question. I have installed ProFTPd on an EC2 instance running Ubuntu 10.10. I have managed my proftpd.conf file as well as my server permissions to be able to connect and upload/move files using FTP both remotely using Filezilla, and on the server itself when connecting to 127.0.0.1. The problem I'm running into is when I try to upload/install a file using Joomla's interface. I give Joomla the same login information that I give to Filezilla, and the connection is made in the same fashion. The ftp.log file actually shows that Joomla is able to login to the server: localhost UNKNOWN nobody [17/Jan/2011:14:09:17 +0000] "USER ftpuser" 331 - localhost UNKNOWN ftpuser [17/Jan/2011:14:09:17 +0000] "PASS (hidden)" 230 - localhost UNKNOWN ftpuser [17/Jan/2011:14:09:17 +0000] "PASV" 227 - localhost UNKNOWN ftpuser [17/Jan/2011:14:09:17 +0000] "TYPE I" 200 - localhost UNKNOWN ftpuser [17/Jan/2011:14:09:17 +0000] "STOR /directory/store/location/file.zip" 550 - But it fails when attempting the STOR command. I have traced the problem in the Joomla code to the PHP FTP module. The code (with my trace statements added): if (@ftp_put($this->_conn, $remote, $local, $mode) === false) { echo "\n FTP PUT failed."; echo "\n Remote: $remote ; Local: $local ; Mode: $mode - Either ASCII: ".FTP_ASCII." or Binary: ".FTP_BINARY; echo "\n The user: ".exec("whoami"); JError::raiseWarning('35', 'JFTP::store: Bad response' ); return false; } Trace ouputs: FTP PUT failed. Remote: /directory/store/location/file.zip ; Local: /tmp/phpwuccp4 ; Mode: 2 - Either ASCII: 1 or Binary: 2 The user: www-data And in case you were curious, here is an example of the FTP log when using Filezilla: my_client_ip UNKNOWN nobody [17/Jan/2011:16:45:55 +0000] "USER ftpuser" 331 - my_client_ip UNKNOWN ftpuser [17/Jan/2011:16:45:55 +0000] "PASS (hidden)" 230 - my_client_ip UNKNOWN ftpuser [17/Jan/2011:16:45:55 +0000] "OPTS UTF8 ON" - - my_client_ip UNKNOWN ftpuser [17/Jan/2011:16:45:55 +0000] "PWD" 257 - my_client_ip UNKNOWN ftpuser [17/Jan/2011:16:45:55 +0000] "TYPE I" 200 - my_client_ip UNKNOWN ftpuser [17/Jan/2011:16:45:55 +0000] "PASV" 227 - my_client_ip UNKNOWN ftpuser [17/Jan/2011:16:45:55 +0000] "MLSD" 226 3405 my_client_ip UNKNOWN ftpuser [17/Jan/2011:16:46:06 +0000] "CWD location" 250 3405 my_client_ip UNKNOWN ftpuser [17/Jan/2011:16:46:06 +0000] "PWD" 257 3405 my_client_ip UNKNOWN ftpuser [17/Jan/2011:16:46:06 +0000] "PASV" 227 3405 my_client_ip UNKNOWN ftpuser [17/Jan/2011:16:46:07 +0000] "MLSD" 226 3757 my_client_ip UNKNOWN nobody [17/Jan/2011:16:46:37 +0000] "USER ftpuser" 331 - my_client_ip UNKNOWN ftpuser [17/Jan/2011:16:46:37 +0000] "PASS (hidden)" 230 - my_client_ip UNKNOWN ftpuser [17/Jan/2011:16:46:37 +0000] "OPTS UTF8 ON" - - my_client_ip UNKNOWN ftpuser [17/Jan/2011:16:46:37 +0000] "CWD /location" 250 - my_client_ip UNKNOWN ftpuser [17/Jan/2011:16:46:37 +0000] "PWD" 257 - my_client_ip UNKNOWN ftpuser [17/Jan/2011:16:46:37 +0000] "TYPE I" 200 - my_client_ip UNKNOWN ftpuser [17/Jan/2011:16:46:37 +0000] "PASV" 227 - my_client_ip UNKNOWN ftpuser [17/Jan/2011:16:46:39 +0000] "STOR file.zip" 226 125317 my_client_ip UNKNOWN ftpuser [17/Jan/2011:16:46:39 +0000] "PASV" 227 - my_client_ip UNKNOWN ftpuser [17/Jan/2011:16:46:39 +0000] "MLSD" 226 497

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• can't access nginx server from IP

  - by EquinoX

  So 2 days ago I can see that page where it saya "Welcome to nginx", however as of now when I tried to access it, it says 404 page not found... Why is this? Inside my sites-enabled folder I have a file named default and it has the following: # You may add here your # server { # ... # } # statements for each of your virtual hosts server { listen 80; server_name 127.0.0.1; access_log /var/log/nginx/localhost.access.log; location / { root /var/www/nginx-default; index index.html index.htm; } location /doc { root /usr/share; autoindex on; allow 127.0.0.1; deny all; } location /images { root /usr/share; autoindex on; } #error_page 404 /404.html; # redirect server error pages to the static page /50x.html # #error_page 500 502 503 504 /50x.html; #location = /50x.html { # root /var/www/nginx-default; #} # proxy the PHP scripts to Apache listening on 127.0.0.1:80 # #location ~ \.php$ { #proxy_pass http://127.0.0.1; #} # pass the PHP scripts to FastCGI server listening on 127.0.0.1:9000 # location ~ \.php$ { fastcgi_pass 127.0.0.1:9000; fastcgi_index index.php; fastcgi_param SCRIPT_FILENAME /var/www/nginx-default$fastcgi_script_name; include fastcgi_params; } # deny access to .htaccess files, if Apache's document root # concurs with nginx's one # location ~ /\.ht { deny all; } } # another virtual host using mix of IP-, name-, and port-based configuration # #server { #listen 8000; #listen somename:8080; #server_name somename alias another.alias; #location / { #root html; #index index.html index.htm; #} #} # HTTPS server # #server { #listen 443; #server_name localhost; #ssl on; #ssl_certificate cert.pem; #ssl_certificate_key cert.key; #ssl_session_timeout 5m; #ssl_protocols SSLv2 SSLv3 TLSv1; #ssl_ciphers ALL:!ADH:!EXPORT56:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP; #ssl_prefer_server_ciphers on; #location / { #root html; #index index.html index.htm; #} #} Here's my nginx.conf file: user www-data; worker_processes 4; error_log /var/log/nginx/error.log; pid /var/run/nginx.pid; events { worker_connections 1024; # multi_accept on; } http { include /etc/nginx/mime.types; access_log /var/log/nginx/access.log; sendfile on; #tcp_nopush on; #keepalive_timeout 0; keepalive_timeout 65; tcp_nodelay on; gzip on; gzip_disable "MSIE [1-6]\.(?!.*SV1)"; include /etc/nginx/conf.d/*.conf; include /etc/nginx/sites-enabled/*; } # mail { # # See sample authentication script at: # # http://wiki.nginx.org/NginxImapAuthenticateWithApachePhpScript # # # auth_http localhost/auth.php; # # pop3_capabilities "TOP" "USER"; # # imap_capabilities "IMAP4rev1" "UIDPLUS"; # # server { # listen localhost:110; # protocol pop3; # proxy on; # } # # server { # listen localhost:143; # protocol imap; # proxy on; # } # } What am I doing wrong here? I have other virtual host setup in the sites-enabled as well... UPDATE: The server_name directives are: -admin.api.frapi -api.frapi -default -example.com -php.example.com

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• Parallelism in .NET – Part 15, Making Tasks Run: The TaskScheduler

  - by Reed

  In my introduction to the Task class, I specifically made mention that the Task class does not directly provide it’s own execution.  In addition, I made a strong point that the Task class itself is not directly related to threads or multithreading.  Rather, the Task class is used to implement our decomposition of tasks.  Once we’ve implemented our tasks, we need to execute them.  In the Task Parallel Library, the execution of Tasks is handled via an instance of the TaskScheduler class. The TaskScheduler class is an abstract class which provides a single function: it schedules the tasks and executes them within an appropriate context.  This class is the class which actually runs individual Task instances.  The .NET Framework provides two (internal) implementations of the TaskScheduler class. Since a Task, based on our decomposition, should be a self-contained piece of code, parallel execution makes sense when executing tasks.  The default implementation of the TaskScheduler class, and the one most often used, is based on the ThreadPool.  This can be retrieved via the TaskScheduler.Default property, and is, by default, what is used when we just start a Task instance with Task.Start(). Normally, when a Task is started by the default TaskScheduler, the task will be treated as a single work item, and run on a ThreadPool thread.  This pools tasks, and provides Task instances all of the advantages of the ThreadPool, including thread pooling for reduced resource usage, and an upper cap on the number of work items.  In addition, .NET 4 brings us a much improved thread pool, providing work stealing and reduced locking within the thread pool queues.  By using the default TaskScheduler, our Tasks are run asynchronously on the ThreadPool. There is one notable exception to my above statements when using the default TaskScheduler.  If a Task is created with the TaskCreationOptions set to TaskCreationOptions.LongRunning, the default TaskScheduler will generate a new thread for that Task, at least in the current implementation.  This is useful for Tasks which will persist for most of the lifetime of your application, since it prevents your Task from starving the ThreadPool of one of it’s work threads. The Task Parallel Library provides one other implementation of the TaskScheduler class.  In addition to providing a way to schedule tasks on the ThreadPool, the framework allows you to create a TaskScheduler which works within a specified SynchronizationContext.  This scheduler can be retrieved within a thread that provides a valid SynchronizationContext by calling the TaskScheduler.FromCurrentSynchronizationContext() method. This implementation of TaskScheduler is intended for use with user interface development.  Windows Forms and Windows Presentation Foundation both require any access to user interface controls to occur on the same thread that created the control.  For example, if you want to set the text within a Windows Forms TextBox, and you’re working on a background thread, that UI call must be marshaled back onto the UI thread.  The most common way this is handled depends on the framework being used.  In Windows Forms, Control.Invoke or Control.BeginInvoke is most often used.  In WPF, the equivelent calls are Dispatcher.Invoke or Dispatcher.BeginInvoke. As an example, say we’re working on a background thread, and we want to update a TextBlock in our user interface with a status label.  The code would typically look something like: // Within background thread work... string status = GetUpdatedStatus(); Dispatcher.BeginInvoke(DispatcherPriority.Normal, new Action( () => { statusLabel.Text = status; })); // Continue on in background method .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } This works fine, but forces your method to take a dependency on WPF or Windows Forms.  There is an alternative option, however.  Both Windows Forms and WPF, when initialized, setup a SynchronizationContext in their thread, which is available on the UI thread via the SynchronizationContext.Current property.  This context is used by classes such as BackgroundWorker to marshal calls back onto the UI thread in a framework-agnostic manner. The Task Parallel Library provides the same functionality via the TaskScheduler.FromCurrentSynchronizationContext() method.  When setting up our Tasks, as long as we’re working on the UI thread, we can construct a TaskScheduler via: TaskScheduler uiScheduler = TaskScheduler.FromCurrentSynchronizationContext(); We then can use this scheduler on any thread to marshal data back onto the UI thread.  For example, our code above can then be rewritten as: string status = GetUpdatedStatus(); (new Task(() => { statusLabel.Text = status; })) .Start(uiScheduler); // Continue on in background method This is nice since it allows us to write code that isn’t tied to Windows Forms or WPF, but is still fully functional with those technologies.  I’ll discuss even more uses for the SynchronizationContext based TaskScheduler when I demonstrate task continuations, but even without continuations, this is a very useful construct. In addition to the two implementations provided by the Task Parallel Library, it is possible to implement your own TaskScheduler.  The ParallelExtensionsExtras project within the Samples for Parallel Programming provides nine sample TaskScheduler implementations.  These include schedulers which restrict the maximum number of concurrent tasks, run tasks on a single threaded apartment thread, use a new thread per task, and more.

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• ASP.NET MVC 3: Implicit and Explicit code nuggets with Razor

  - by ScottGu

  This is another in a series of posts I’m doing that cover some of the new ASP.NET MVC 3 features: New @model keyword in Razor (Oct 19th) Layouts with Razor (Oct 22nd) Server-Side Comments with Razor (Nov 12th) Razor’s @: and <text> syntax (Dec 15th) Implicit and Explicit code nuggets with Razor (today) In today’s post I’m going to discuss how Razor enables you to both implicitly and explicitly define code nuggets within your view templates, and walkthrough some code examples of each of them.  Fluid Coding with Razor ASP.NET MVC 3 ships with a new view-engine option called “Razor” (in addition to the existing .aspx view engine).  You can learn more about Razor, why we are introducing it, and the syntax it supports from my Introducing Razor blog post. Razor minimizes the number of characters and keystrokes required when writing a view template, and enables a fast, fluid coding workflow. Unlike most template syntaxes, you do not need to interrupt your coding to explicitly denote the start and end of server blocks within your HTML. The Razor parser is smart enough to infer this from your code. This enables a compact and expressive syntax which is clean, fast and fun to type. For example, the Razor snippet below can be used to iterate a collection of products and output a <ul> list of product names that link to their corresponding product pages: When run, the above code generates output like below: Notice above how we were able to embed two code nuggets within the content of the foreach loop.  One of them outputs the name of the Product, and the other embeds the ProductID within a hyperlink.  Notice that we didn’t have to explicitly wrap these code-nuggets - Razor was instead smart enough to implicitly identify where the code began and ended in both of these situations.  How Razor Enables Implicit Code Nuggets Razor does not define its own language.  Instead, the code you write within Razor code nuggets is standard C# or VB.  This allows you to re-use your existing language skills, and avoid having to learn a customized language grammar. The Razor parser has smarts built into it so that whenever possible you do not need to explicitly mark the end of C#/VB code nuggets you write.  This makes coding more fluid and productive, and enables a nice, clean, concise template syntax.  Below are a few scenarios that Razor supports where you can avoid having to explicitly mark the beginning/end of a code nugget, and instead have Razor implicitly identify the code nugget scope for you: Property Access Razor allows you to output a variable value, or a sub-property on a variable that is referenced via “dot” notation: You can also use “dot” notation to access sub-properties multiple levels deep: Array/Collection Indexing: Razor allows you to index into collections or arrays: Calling Methods: Razor also allows you to invoke methods: Notice how for all of the scenarios above how we did not have to explicitly end the code nugget.  Razor was able to implicitly identify the end of the code block for us. Razor’s Parsing Algorithm for Code Nuggets The below algorithm captures the core parsing logic we use to support “@” expressions within Razor, and to enable the implicit code nugget scenarios above: Parse an identifier - As soon as we see a character that isn't valid in a C# or VB identifier, we stop and move to step 2 Check for brackets - If we see "(" or "[", go to step 2.1., otherwise, go to step 3  Parse until the matching ")" or "]" (we track nested "()" and "[]" pairs and ignore "()[]" we see in strings or comments) Go back to step 2 Check for a "." - If we see one, go to step 3.1, otherwise, DO NOT ACCEPT THE "." as code, and go to step 4 If the character AFTER the "." is a valid identifier, accept the "." and go back to step 1, otherwise, go to step 4 Done! Differentiating between code and content Step 3.1 is a particularly interesting part of the above algorithm, and enables Razor to differentiate between scenarios where an identifier is being used as part of the code statement, and when it should instead be treated as static content: Notice how in the snippet above we have ? and ! characters at the end of our code nuggets.  These are both legal C# identifiers – but Razor is able to implicitly identify that they should be treated as static string content as opposed to being part of the code expression because there is whitespace after them.  This is pretty cool and saves us keystrokes. Explicit Code Nuggets in Razor Razor is smart enough to implicitly identify a lot of code nugget scenarios.  But there are still times when you want/need to be more explicit in how you scope the code nugget expression.  The @(expression) syntax allows you to do this: You can write any C#/VB code statement you want within the @() syntax.  Razor will treat the wrapping () characters as the explicit scope of the code nugget statement.  Below are a few scenarios where we could use the explicit code nugget feature: Perform Arithmetic Calculation/Modification: You can perform arithmetic calculations within an explicit code nugget: Appending Text to a Code Expression Result: You can use the explicit expression syntax to append static text at the end of a code nugget without having to worry about it being incorrectly parsed as code: Above we have embedded a code nugget within an <img> element’s src attribute.  It allows us to link to images with URLs like “/Images/Beverages.jpg”.  Without the explicit parenthesis, Razor would have looked for a “.jpg” property on the CategoryName (and raised an error).  By being explicit we can clearly denote where the code ends and the text begins. Using Generics and Lambdas Explicit expressions also allow us to use generic types and generic methods within code expressions – and enable us to avoid the <> characters in generics from being ambiguous with tag elements. One More Thing….Intellisense within Attributes We have used code nuggets within HTML attributes in several of the examples above.  One nice feature supported by the Razor code editor within Visual Studio is the ability to still get VB/C# intellisense when doing this. Below is an example of C# code intellisense when using an implicit code nugget within an <a> href=”” attribute: Below is an example of C# code intellisense when using an explicit code nugget embedded in the middle of a <img> src=”” attribute: Notice how we are getting full code intellisense for both scenarios – despite the fact that the code expression is embedded within an HTML attribute (something the existing .aspx code editor doesn’t support).  This makes writing code even easier, and ensures that you can take advantage of intellisense everywhere. Summary Razor enables a clean and concise templating syntax that enables a very fluid coding workflow.  Razor’s ability to implicitly scope code nuggets reduces the amount of typing you need to perform, and leaves you with really clean code. When necessary, you can also explicitly scope code expressions using a @(expression) syntax to provide greater clarity around your intent, as well as to disambiguate code statements from static markup. Hope this helps, Scott P.S. In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu

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• BNF – how to read syntax?

  - by Piotr Rodak

  A few days ago I read post of Jen McCown (blog) about her idea of blogging about random articles from Books Online. I think this is a great idea, even if Jen says that it’s not exciting or sexy. I noticed that many of the questions that appear on forums and other media arise from pure fact that people asking questions didn’t bother to read and understand the manual – Books Online. Jen came up with a brilliant, concise acronym that describes very well the category of posts about Books Online – RTFM365. I take liberty of tagging this post with the same acronym. I often come across questions of type – ‘Hey, i am trying to create a table, but I am getting an error’. The error often says that the syntax is invalid. 1 CREATE TABLE dbo.Employees 2 (guid uniqueidentifier CONSTRAINT DEFAULT Guid_Default NEWSEQUENTIALID() ROWGUIDCOL, 3 Employee_Name varchar(60) 4 CONSTRAINT Guid_PK PRIMARY KEY (guid) ); 5 The answer is usually(1), ‘Ok, let me check it out.. Ah yes – you have to put name of the DEFAULT constraint before the type of constraint: 1 CREATE TABLE dbo.Employees 2 (guid uniqueidentifier CONSTRAINT Guid_Default DEFAULT NEWSEQUENTIALID() ROWGUIDCOL, 3 Employee_Name varchar(60) 4 CONSTRAINT Guid_PK PRIMARY KEY (guid) ); Why many people stumble on syntax errors? Is the syntax poorly documented? No, the issue is, that correct syntax of the CREATE TABLE statement is documented very well in Books Online and is.. intimidating. Many people can be taken aback by the rather complex block of code that describes all intricacies of the statement. However, I don’t know better way of defining syntax of the statement or command. The notation that is used to describe syntax in Books Online is a form of Backus-Naur notatiion, called BNF for short sometimes. This is a notation that was invented around 50 years ago, and some say that even earlier, around 400 BC – would you believe? Originally it was used to define syntax of, rather ancient now, ALGOL programming language (in 1950’s, not in ancient India). If you look closer at the definition of the BNF, it turns out that the principles of this syntax are pretty simple. Here are a few bullet points: italic_text is a placeholder for your identifier <italic_text_in_angle_brackets> is a definition which is described further. [everything in square brackets] is optional {everything in curly brackets} is obligatory everything | separated | by | operator is an alternative ::= “assigns” definition to an identifier Yes, it looks like these six simple points give you the key to understand even the most complicated syntax definitions in Books Online. Books Online contain an article about syntax conventions – have you ever read it? Let’s have a look at fragment of the CREATE TABLE statement: 1 CREATE TABLE 2 [ database_name . [ schema_name ] . | schema_name . ] table_name 3 ( { <column_definition> | <computed_column_definition> 4 | <column_set_definition> } 5 [ <table_constraint> ] [ ,...n ] ) 6 [ ON { partition_scheme_name ( partition_column_name ) | filegroup 7 | "default" } ] 8 [ { TEXTIMAGE_ON { filegroup | "default" } ] 9 [ FILESTREAM_ON { partition_scheme_name | filegroup 10 | "default" } ] 11 [ WITH ( <table_option> [ ,...n ] ) ] 12 [ ; ] Let’s look at line 2 of the above snippet: This line uses rules 3 and 5 from the list. So you know that you can create table which has specified one of the following. just name – table will be created in default user schema schema name and table name – table will be created in specified schema database name, schema name and table name – table will be created in specified database, in specified schema database name, .., table name – table will be created in specified database, in default schema of the user. Note that this single line of the notation describes each of the naming schemes in deterministic way. The ‘optionality’ of the schema_name element is nested within database_name.. section. You can use either database_name and optional schema name, or just schema name – this is specified by the pipe character ‘|’. The error that user gets with execution of the first script fragment in this post is as follows: Msg 156, Level 15, State 1, Line 2 Incorrect syntax near the keyword 'DEFAULT'. Ok, let’s have a look how to find out the correct syntax. Line number 3 of the BNF fragment above contains reference to <column_definition>. Since column_definition is in angle brackets, we know that this is a reference to notion described further in the code. And indeed, the very next fragment of BNF contains syntax of the column definition. 1 <column_definition> ::= 2 column_name <data_type> 3 [ FILESTREAM ] 4 [ COLLATE collation_name ] 5 [ NULL | NOT NULL ] 6 [ 7 [ CONSTRAINT constraint_name ] DEFAULT constant_expression ] 8 | [ IDENTITY [ ( seed ,increment ) ] [ NOT FOR REPLICATION ] 9 ] 10 [ ROWGUIDCOL ] [ <column_constraint> [ ...n ] ] 11 [ SPARSE ] Look at line 7 in the above fragment. It says, that the column can have a DEFAULT constraint which, if you want to name it, has to be prepended with [CONSTRAINT constraint_name] sequence. The name of the constraint is optional, but I strongly recommend you to make the effort of coming up with some meaningful name yourself. So the correct syntax of the CREATE TABLE statement from the beginning of the article is like this: 1 CREATE TABLE dbo.Employees 2 (guid uniqueidentifier CONSTRAINT Guid_Default DEFAULT NEWSEQUENTIALID() ROWGUIDCOL, 3 Employee_Name varchar(60) 4 CONSTRAINT Guid_PK PRIMARY KEY (guid) ); That is practically everything you should know about BNF. I encourage you to study the syntax definitions for various statements and commands in Books Online, you can find really interesting things hidden there. Technorati Tags: SQL Server,t-sql,BNF,syntax   (1) No, my answer usually is a question – ‘What error message? What does it say?’. You’d be surprised to know how many people think I can go through time and space and look at their screen at the moment they received the error.

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• SQL SERVER – How to Recover SQL Database Data Deleted by Accident

  - by Pinal Dave

  In Repair a SQL Server database using a transaction log explorer, I showed how to use ApexSQL Log, a SQL Server transaction log viewer, to recover a SQL Server database after a disaster. In this blog, I’ll show you how to use another SQL Server disaster recovery tool from ApexSQL in a situation when data is accidentally deleted. You can download ApexSQL Recover here, install, and play along. With a good SQL Server disaster recovery strategy, data recovery is not a problem. You have a reliable full database backup with valid data, a full database backup and subsequent differential database backups, or a full database backup and a chain of transaction log backups. But not all situations are ideal. Here we’ll address some sub-optimal scenarios, where you can still successfully recover data. If you have only a full database backup This is the least optimal SQL Server disaster recovery strategy, as it doesn’t ensure minimal data loss. For example, data was deleted on Wednesday. Your last full database backup was created on Sunday, three days before the records were deleted. By using the full database backup created on Sunday, you will be able to recover SQL database records that existed in the table on Sunday. If there were any records inserted into the table on Monday or Tuesday, they will be lost forever. The same goes for records modified in this period. This method will not bring back modified records, only the old records that existed on Sunday. If you restore this full database backup, all your changes (intentional and accidental) will be lost and the database will be reverted to the state it had on Sunday. What you have to do is compare the records that were in the table on Sunday to the records on Wednesday, create a synchronization script, and execute it against the Wednesday database. If you have a full database backup followed by differential database backups Let’s say the situation is the same as in the example above, only you create a differential database backup every night. Use the full database backup created on Sunday, and the last differential database backup (created on Tuesday). In this scenario, you will lose only the data inserted and updated after the differential backup created on Tuesday. If you have a full database backup and a chain of transaction log backups This is the SQL Server disaster recovery strategy that provides minimal data loss. With a full chain of transaction logs, you can recover the SQL database to an exact point in time. To provide optimal results, you have to know exactly when the records were deleted, because restoring to a later point will not bring back the records. This method requires restoring the full database backup first. If you have any differential log backup created after the last full database backup, restore the most recent one. Then, restore transaction log backups, one by one, it the order they were created starting with the first created after the restored differential database backup. Now, the table will be in the state before the records were deleted. You have to identify the deleted records, script them and run the script against the original database. Although this method is reliable, it is time-consuming and requires a lot of space on disk. How to easily recover deleted records? The following solution enables you to recover SQL database records even if you have no full or differential database backups and no transaction log backups. To understand how ApexSQL Recover works, I’ll explain what happens when table data is deleted. Table data is stored in data pages. When you delete table records, they are not immediately deleted from the data pages, but marked to be overwritten by new records. Such records are not shown as existing anymore, but ApexSQL Recover can read them and create undo script for them. How long will deleted records stay in the MDF file? It depends on many factors, as time passes it’s less likely that the records will not be overwritten. The more transactions occur after the deletion, the more chances the records will be overwritten and permanently lost. Therefore, it’s recommended to create a copy of the database MDF and LDF files immediately (if you cannot take your database offline until the issue is solved) and run ApexSQL Recover on them. Note that a full database backup will not help here, as the records marked for overwriting are not included in the backup. First, I’ll delete some records from the Person.EmailAddress table in the AdventureWorks database.   I can delete these records in SQL Server Management Studio, or execute a script such as DELETE FROM Person.EmailAddress WHERE BusinessEntityID BETWEEN 70 AND 80 Then, I’ll start ApexSQL Recover and select From DELETE operation in the Recovery tab.   In the Select the database to recover step, first select the SQL Server instance. If it’s not shown in the drop-down list, click the Server icon right to the Server drop-down list and browse for the SQL Server instance, or type the instance name manually. Specify the authentication type and select the database in the Database drop-down list.   In the next step, you’re prompted to add additional data sources. As this can be a tricky step, especially for new users, ApexSQL Recover offers help via the Help me decide option.   The Help me decide option guides you through a series of questions about the database transaction log and advises what files to add. If you know that you have no transaction log backups or detached transaction logs, or the online transaction log file has been truncated after the data was deleted, select No additional transaction logs are available. If you know that you have transaction log backups that contain the delete transactions you want to recover, click Add transaction logs. The online transaction log is listed and selected automatically.   Click Add if to add transaction log backups. It would be best if you have a full transaction log chain, as explained above. The next step for this option is to specify the time range.   Selecting a small time range for the time of deletion will create the recovery script just for the accidentally deleted records. A wide time range might script the records deleted on purpose, and you don’t want that. If needed, you can check the script generated and manually remove such records. After that, for all data sources options, the next step is to select the tables. Be careful here, if you deleted some data from other tables on purpose, and don’t want to recover them, don’t select all tables, as ApexSQL Recover will create the INSERT script for them too.   The next step offers two options: to create a recovery script that will insert the deleted records back into the Person.EmailAddress table, or to create a new database, create the Person.EmailAddress table in it, and insert the deleted records. I’ll select the first one.   The recovery process is completed and 11 records are found and scripted, as expected.   To see the script, click View script. ApexSQL Recover has its own script editor, where you can review, modify, and execute the recovery script. The insert into statements look like: INSERT INTO Person.EmailAddress( BusinessEntityID, EmailAddressID, EmailAddress, rowguid, ModifiedDate) VALUES( 70, 70, N'[email protected]' COLLATE SQL_Latin1_General_CP1_CI_AS, 'd62c5b4e-c91f-403f-b630-7b7e0fda70ce', '20030109 00:00:00.000' ); To execute the script, click Execute in the menu.   If you want to check whether the records are really back, execute SELECT * FROM Person.EmailAddress WHERE BusinessEntityID BETWEEN 70 AND 80 As shown, ApexSQL Recover recovers SQL database data after accidental deletes even without the database backup that contains the deleted data and relevant transaction log backups. ApexSQL Recover reads the deleted data from the database data file, so this method can be used even for databases in the Simple recovery model. Besides recovering SQL database records from a DELETE statement, ApexSQL Recover can help when the records are lost due to a DROP TABLE, or TRUNCATE statement, as well as repair a corrupted MDF file that cannot be attached to as SQL Server instance. You can find more information about how to recover SQL database lost data and repair a SQL Server database on ApexSQL Solution center. There are solutions for various situations when data needs to be recovered. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: PostADay, SQL, SQL Authority, SQL Backup and Restore, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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• Dynamic Types and DynamicObject References in C#

  - by Rick Strahl

  I've been working a bit with C# custom dynamic types for several customers recently and I've seen some confusion in understanding how dynamic types are referenced. This discussion specifically centers around types that implement IDynamicMetaObjectProvider or subclass from DynamicObject as opposed to arbitrary type casts of standard .NET types. IDynamicMetaObjectProvider types  are treated special when they are cast to the dynamic type. Assume for a second that I've created my own implementation of a custom dynamic type called DynamicFoo which is about as simple of a dynamic class that I can think of:public class DynamicFoo : DynamicObject { Dictionary<string, object> properties = new Dictionary<string, object>(); public string Bar { get; set; } public DateTime Entered { get; set; } public override bool TryGetMember(GetMemberBinder binder, out object result) { result = null; if (!properties.ContainsKey(binder.Name)) return false; result = properties[binder.Name]; return true; } public override bool TrySetMember(SetMemberBinder binder, object value) { properties[binder.Name] = value; return true; } } This class has an internal dictionary member and I'm exposing this dictionary member through a dynamic by implementing DynamicObject. This implementation exposes the properties dictionary so the dictionary keys can be referenced like properties (foo.NewProperty = "Cool!"). I override TryGetMember() and TrySetMember() which are fired at runtime every time you access a 'property' on a dynamic instance of this DynamicFoo type. Strong Typing and Dynamic Casting I now can instantiate and use DynamicFoo in a couple of different ways: Strong TypingDynamicFoo fooExplicit = new DynamicFoo(); var fooVar = new DynamicFoo(); These two commands are essentially identical and use strong typing. The compiler generates identical code for both of them. The var statement is merely a compiler directive to infer the type of fooVar at compile time and so the type of fooExplicit is DynamicFoo, just like fooExplicit. This is very static - nothing dynamic about it - and it completely ignores the IDynamicMetaObjectProvider implementation of my class above as it's never used. Using either of these I can access the native properties:DynamicFoo fooExplicit = new DynamicFoo();// static typing assignmentsfooVar.Bar = "Barred!"; fooExplicit.Entered = DateTime.Now; // echo back static values Console.WriteLine(fooVar.Bar); Console.WriteLine(fooExplicit.Entered); but I have no access whatsoever to the properties dictionary. Basically this creates a strongly typed instance of the type with access only to the strongly typed interface. You get no dynamic behavior at all. The IDynamicMetaObjectProvider features don't kick in until you cast the type to dynamic. If I try to access a non-existing property on fooExplicit I get a compilation error that tells me that the property doesn't exist. Again, it's clearly and utterly non-dynamic. Dynamicdynamic fooDynamic = new DynamicFoo(); fooDynamic on the other hand is created as a dynamic type and it's a completely different beast. I can also create a dynamic by simply casting any type to dynamic like this:DynamicFoo fooExplicit = new DynamicFoo(); dynamic fooDynamic = fooExplicit; Note that dynamic typically doesn't require an explicit cast as the compiler automatically performs the cast so there's no need to use as dynamic. Dynamic functionality works at runtime and allows for the dynamic wrapper to look up and call members dynamically. A dynamic type will look for members to access or call in two places: Using the strongly typed members of the object Using theIDynamicMetaObjectProvider Interface methods to access members So rather than statically linking and calling a method or retrieving a property, the dynamic type looks up - at runtime  - where the value actually comes from. It's essentially late-binding which allows runtime determination what action to take when a member is accessed at runtime *if* the member you are accessing does not exist on the object. Class members are checked first before IDynamicMetaObjectProvider interface methods are kick in. All of the following works with the dynamic type:dynamic fooDynamic = new DynamicFoo(); // dynamic typing assignments fooDynamic.NewProperty = "Something new!"; fooDynamic.LastAccess = DateTime.Now; // dynamic assigning static properties fooDynamic.Bar = "dynamic barred"; fooDynamic.Entered = DateTime.Now; // echo back dynamic values Console.WriteLine(fooDynamic.NewProperty); Console.WriteLine(fooDynamic.LastAccess); Console.WriteLine(fooDynamic.Bar); Console.WriteLine(fooDynamic.Entered); The dynamic type can access the native class properties (Bar and Entered) and create and read new ones (NewProperty,LastAccess) all using a single type instance which is pretty cool. As you can see it's pretty easy to create an extensible type this way that can dynamically add members at runtime dynamically. The Alter Ego of IDynamicObject The key point here is that all three statements - explicit, var and dynamic - declare a new DynamicFoo(), but the dynamic declaration results in completely different behavior than the first two simply because the type has been cast to dynamic. Dynamic binding means that the type loses its typical strong typing, compile time features. You can see this easily in the Visual Studio code editor. As soon as you assign a value to a dynamic you lose Intellisense and you see which means there's no Intellisense and no compiler type checking on any members you apply to this instance. If you're new to the dynamic type it might seem really confusing that a single type can behave differently depending on how it is cast, but that's exactly what happens when you use a type that implements IDynamicMetaObjectProvider. Declare the type as its strong type name and you only get to access the native instance members of the type. Declare or cast it to dynamic and you get dynamic behavior which accesses native members plus it uses IDynamicMetaObjectProvider implementation to handle any missing member definitions by running custom code. You can easily cast objects back and forth between dynamic and the original type:dynamic fooDynamic = new DynamicFoo(); fooDynamic.NewProperty = "New Property Value"; DynamicFoo foo = fooDynamic; foo.Bar = "Barred"; Here the code starts out with a dynamic cast and a dynamic assignment. The code then casts back the value to the DynamicFoo. Notice that when casting from dynamic to DynamicFoo and back we typically do not have to specify the cast explicitly - the compiler can induce the type so I don't need to specify as dynamic or as DynamicFoo. Moral of the Story This easy interchange between dynamic and the underlying type is actually super useful, because it allows you to create extensible objects that can expose non-member data stores and expose them as an object interface. You can create an object that hosts a number of strongly typed properties and then cast the object to dynamic and add additional dynamic properties to the same type at runtime. You can easily switch back and forth between the strongly typed instance to access the well-known strongly typed properties and to dynamic for the dynamic properties added at runtime. Keep in mind that dynamic object access has quite a bit of overhead and is definitely slower than strongly typed binding, so if you're accessing the strongly typed parts of your objects you definitely want to use a strongly typed reference. Reserve dynamic for the dynamic members to optimize your code. The real beauty of dynamic is that with very little effort you can build expandable objects or objects that expose different data stores to an object interface. I'll have more on this in my next post when I create a customized and extensible Expando object based on DynamicObject.© Rick Strahl, West Wind Technologies, 2005-2012Posted in CSharp  .NET   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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• T4 Template error - Assembly Directive cannot locate referenced assembly in Visual Studio 2010 proje

  - by CodeSniper

  I ran into the following error recently in Visual Studio 2010 while trying to port Phil Haack’s excellent T4CSS template which was originally built for Visual Studio 2008.   The Problem Error Compiling transformation: Metadata file 'dotless.Core' could not be found In “T4 speak”, this simply means that you have an Assembly directive in your T4 template but the T4 engine was not able to locate or load the referenced assembly. In the case of the T4CSS Template, this was a showstopper for making it work in Visual Studio 2010. On a side note: The T4CSS template is a sweet little wrapper to allow you to use DotLessCss to generate static .css files from .less files rather than using their default HttpHandler or command-line tool.    If you haven't tried DotLessCSS yet, go check it out now!  In short, it is a tool that allows you to templatize and program your CSS files so that you can use variables, expressions, and mixins within your CSS which enables rapid changes and a lot of developer-flexibility as you evolve your CSS and UI. Back to our regularly scheduled program… Anyhow, this post isn't about DotLessCss, its about the T4 Templates and the errors I ran into when converting them from Visual Studio 2008 to Visual Studio 2010. In VS2010, there were quite a few changes to the T4 Template Engine; most were excellent changes, but this one bit me with T4CSS: “Project assemblies are no longer used to resolve template assembly directives.” In VS2008, if you wanted to reference a custom assembly in your T4 Template (.tt file) you would simply right click on your project, choose Add Reference and select that assembly.  Afterwards you were allowed to use the following syntax in your T4 template to tell it to look at the local references: <#@ assembly name="dotless.Core.dll" #> This told the engine to look in the “usual place” for the assembly, which is your project references. However, this is exactly what they changed in VS2010.  They now basically sandbox the T4 Engine to keep your T4 assemblies separate from your project assemblies.  This can come in handy if you want to support different versions of an assembly referenced both by your T4 templates and your project. Who broke the build?  Oh, Microsoft Did! In our case, this change causes a problem since the templates are no longer compatible when upgrading to VS 2010 – thus its a breaking change.  So, how do we make this work in VS 2010? Luckily, Microsoft now offers several options for referencing assemblies from T4 Templates: GAC your assemblies and use Namespace Reference or Fully Qualified Type Name Use a hard-coded Fully Qualified UNC path Copy assembly to Visual Studio "Public Assemblies Folder" and use Namespace Reference or Fully Qualified Type Name.  Use or Define a Windows Environment Variable to build a Fully Qualified UNC path. Use a Visual Studio Macro to build a Fully Qualified UNC path. Option #1 & 2 were already supported in Visual Studio 2008, so if you want to keep your templates compatible with both Visual Studio versions, then you would have to adopt one of these approaches. Yakkety Yak, use the GAC! Option #1 requires an additional pre-build step to GAC the referenced assembly, which could be a pain.  But, if you go that route, then after you GAC, all you need is a simple type name or namespace reference such as: <#@ assembly name="dotless.Core" #> Hard Coding aint that hard! The other option of using hard-coded paths in Option #2 is pretty impractical in most situations since each developer would have to use the same local project folder paths, or modify this setting each time for their local machines as well as for production deployment.  However, if you want to go that route, simply use the following assembly directive style: <#@ assembly name="C:\Code\Lib\dotless.Core.dll" #> Lets go Public! Option #3, the Visual Studio Public Assemblies Folder, is the recommended place to put commonly used tools and libraries that are only needed for Visual Studio.  Think of it like a VS-only GAC.  This is likely the best place for something like dotLessCSS and is my preferred solution.  However, you will need to either use an installer or a pre-build action to copy the assembly to the right folder location.   Normally this is located at:  C:\Program Files (x86)\Microsoft Visual Studio 10.0\Common7\IDE\PublicAssemblies Once you have copied your assembly there, you use the type name or namespace syntax again: <#@ assembly name="dotless.Core" #> Save the Environment! Option #4, using a Windows Environment Variable, is interesting for enterprise use where you may have standard locations for files, but less useful for demo-code, frameworks, and products where you don't have control over the local system.  The syntax for including a environment variable in your assembly directive looks like the following, just as you would expect: <#@ assembly name="%mypath%\dotless.Core.dll" #> “mypath” is a Windows environment variable you setup that points to some fully qualified UNC path on your system.  In the right situation this can be a great solution such as one where you use a msi installer for deployment, or where you have a pre-existing environment variable you can re-use. OMG Macros! Finally, Option #5 is a very nice option if you want to keep your T4 template’s assembly reference local and relative to the project or solution without muddying-up your dev environment or GAC with extra deployments.  An example looks like this: <#@ assembly name="$(SolutionDir)lib\dotless.Core.dll" #> In this example, I’m using the “SolutionDir” VS macro so I can reference an assembly in a “/lib” folder at the root of the solution.   This is just one of the many macros you can use.  If you are familiar with creating Pre/Post-build Event scripts, you can use its dialog to look at all of the different VS macros available. This option gives the best solution for local assemblies without the hassle of extra installers or other setup before the build.   However, its still not compatible with Visual Studio 2008, so if you have a T4 Template you want to use with both, then you may have to create multiple .tt files, one for each IDE version, or require the developer to set a value in the .tt file manually.   I’m not sure if T4 Templates support any form of compiler switches like “#if (VS2010)”  statements, but it would definitely be nice in this case to switch between this option and one of the ones more compatible with VS 2008. Conclusion As you can see, we went from 3 options with Visual Studio 2008, to 5 options (plus one problem) with Visual Studio 2010.  As a whole, I think the changes are great, but the short-term growing pains during the migration may be annoying until we get used to our new found power. Hopefully this all made sense and was helpful to you.  If nothing else, I’ll just use it as a reference the next time I need to port a T4 template to Visual Studio 2010.  Happy T4 templating, and “May the fourth be with you!”

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• A Guided Tour of Complexity

  - by JoshReuben

  I just re-read Complexity – A Guided Tour by Melanie Mitchell , protégé of Douglas Hofstadter ( author of “Gödel, Escher, Bach”) http://www.amazon.com/Complexity-Guided-Tour-Melanie-Mitchell/dp/0199798109/ref=sr_1_1?ie=UTF8&qid=1339744329&sr=8-1 here are some notes and links:   Evolved from Cybernetics, General Systems Theory, Synergetics some interesting transdisciplinary fields to investigate: Chaos Theory - http://en.wikipedia.org/wiki/Chaos_theory – small differences in initial conditions (such as those due to rounding errors in numerical computation) yield widely diverging outcomes for chaotic systems, rendering long-term prediction impossible. System Dynamics / Cybernetics - http://en.wikipedia.org/wiki/System_Dynamics – study of how feedback changes system behavior Network Theory - http://en.wikipedia.org/wiki/Network_theory – leverage Graph Theory to analyze symmetric  / asymmetric relations between discrete objects Algebraic Topology - http://en.wikipedia.org/wiki/Algebraic_topology – leverage abstract algebra to analyze topological spaces There are limits to deterministic systems & to computation. Chaos Theory definitely applies to training an ANN (artificial neural network) – different weights will emerge depending upon the random selection of the training set. In recursive Non-Linear systems http://en.wikipedia.org/wiki/Nonlinear_system – output is not directly inferable from input. E.g. a Logistic map: Xt+1 = R Xt(1-Xt) Different types of bifurcations, attractor states and oscillations may occur – e.g. a Lorenz Attractor http://en.wikipedia.org/wiki/Lorenz_system Feigenbaum Constants http://en.wikipedia.org/wiki/Feigenbaum_constants express ratios in a bifurcation diagram for a non-linear map – the convergent limit of R (the rate of period-doubling bifurcations) is 4.6692016 Maxwell’s Demon - http://en.wikipedia.org/wiki/Maxwell%27s_demon - the Second Law of Thermodynamics has only a statistical certainty – the universe (and thus information) tends towards entropy. While any computation can theoretically be done without expending energy, with finite memory, the act of erasing memory is permanent and increases entropy. Life & thought is a counter-example to the universe’s tendency towards entropy. Leo Szilard and later Claude Shannon came up with the Information Theory of Entropy - http://en.wikipedia.org/wiki/Entropy_(information_theory) whereby Shannon entropy quantifies the expected value of a message’s information in bits in order to determine channel capacity and leverage Coding Theory (compression analysis). Ludwig Boltzmann came up with Statistical Mechanics - http://en.wikipedia.org/wiki/Statistical_mechanics – whereby our Newtonian perception of continuous reality is a probabilistic and statistical aggregate of many discrete quantum microstates. This is relevant for Quantum Information Theory http://en.wikipedia.org/wiki/Quantum_information and the Physics of Information - http://en.wikipedia.org/wiki/Physical_information. Hilbert’s Problems http://en.wikipedia.org/wiki/Hilbert's_problems pondered whether mathematics is complete, consistent, and decidable (the Decision Problem – http://en.wikipedia.org/wiki/Entscheidungsproblem – is there always an algorithm that can determine whether a statement is true).  Godel’s Incompleteness Theorems http://en.wikipedia.org/wiki/G%C3%B6del's_incompleteness_theorems  proved that mathematics cannot be both complete and consistent (e.g. “This statement is not provable”). Turing through the use of Turing Machines (http://en.wikipedia.org/wiki/Turing_machine symbol processors that can prove mathematical statements) and Universal Turing Machines (http://en.wikipedia.org/wiki/Universal_Turing_machine Turing Machines that can emulate other any Turing Machine via accepting programs as well as data as input symbols) that computation is limited by demonstrating the Halting Problem http://en.wikipedia.org/wiki/Halting_problem (is is not possible to know when a program will complete – you cannot build an infinite loop detector). You may be used to thinking of 1 / 2 / 3 dimensional systems, but Fractal http://en.wikipedia.org/wiki/Fractal systems are defined by self-similarity & have non-integer Hausdorff Dimensions !!!  http://en.wikipedia.org/wiki/List_of_fractals_by_Hausdorff_dimension – the fractal dimension quantifies the number of copies of a self similar object at each level of detail – eg Koch Snowflake - http://en.wikipedia.org/wiki/Koch_snowflake Definitions of complexity: size, Shannon entropy, Algorithmic Information Content (http://en.wikipedia.org/wiki/Algorithmic_information_theory - size of shortest program that can generate a description of an object) Logical depth (amount of info processed), thermodynamic depth (resources required). Complexity is statistical and fractal. John Von Neumann’s other machine was the Self-Reproducing Automaton http://en.wikipedia.org/wiki/Self-replicating_machine  . Cellular Automata http://en.wikipedia.org/wiki/Cellular_automaton are alternative form of Universal Turing machine to traditional Von Neumann machines where grid cells are locally synchronized with their neighbors according to a rule. Conway’s Game of Life http://en.wikipedia.org/wiki/Conway's_Game_of_Life demonstrates various emergent constructs such as “Glider Guns” and “Spaceships”. Cellular Automatons are not practical because logical ops require a large number of cells – wasteful & inefficient. There are no compilers or general program languages available for Cellular Automatons (as far as I am aware). Random Boolean Networks http://en.wikipedia.org/wiki/Boolean_network are extensions of cellular automata where nodes are connected at random (not to spatial neighbors) and each node has its own rule –> they demonstrate the emergence of complex  & self organized behavior. Stephen Wolfram’s (creator of Mathematica, so give him the benefit of the doubt) New Kind of Science http://en.wikipedia.org/wiki/A_New_Kind_of_Science proposes the universe may be a discrete Finite State Automata http://en.wikipedia.org/wiki/Finite-state_machine whereby reality emerges from simple rules. I am 2/3 through this book. It is feasible that the universe is quantum discrete at the plank scale and that it computes itself – Digital Physics: http://en.wikipedia.org/wiki/Digital_physics – a simulated reality? Anyway, all behavior is supposedly derived from simple algorithmic rules & falls into 4 patterns: uniform , nested / cyclical, random (Rule 30 http://en.wikipedia.org/wiki/Rule_30) & mixed (Rule 110 - http://en.wikipedia.org/wiki/Rule_110 localized structures – it is this that is interesting). interaction between colliding propagating signal inputs is then information processing. Wolfram proposes the Principle of Computational Equivalence - http://mathworld.wolfram.com/PrincipleofComputationalEquivalence.html - all processes that are not obviously simple can be viewed as computations of equivalent sophistication. Meaning in information may emerge from analogy & conceptual slippages – see the CopyCat program: http://cognitrn.psych.indiana.edu/rgoldsto/courses/concepts/copycat.pdf Scale Free Networks http://en.wikipedia.org/wiki/Scale-free_network have a distribution governed by a Power Law (http://en.wikipedia.org/wiki/Power_law - much more common than Normal Distribution). They are characterized by hubs (resilience to random deletion of nodes), heterogeneity of degree values, self similarity, & small world structure. They grow via preferential attachment http://en.wikipedia.org/wiki/Preferential_attachment – tipping points triggered by positive feedback loops. 2 theories of cascading system failures in complex systems are Self-Organized Criticality http://en.wikipedia.org/wiki/Self-organized_criticality and Highly Optimized Tolerance http://en.wikipedia.org/wiki/Highly_optimized_tolerance. Computational Mechanics http://en.wikipedia.org/wiki/Computational_mechanics – use of computational methods to study phenomena governed by the principles of mechanics. This book is a great intuition pump, but does not cover the more mathematical subject of Computational Complexity Theory – http://en.wikipedia.org/wiki/Computational_complexity_theory I am currently reading this book on this subject: http://www.amazon.com/Computational-Complexity-Christos-H-Papadimitriou/dp/0201530821/ref=pd_sim_b_1   stay tuned for that review!

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• C# in Depth, Third Edition by Jon Skeet, Manning Publications Co. Book Review

  - by Compudicted

  Originally posted on: http://geekswithblogs.net/Compudicted/archive/2013/10/24/c-in-depth-third-edition-by-jon-skeet-manning-publications.aspx I started reading this ebook on September 28, 2013, the same day it was sent my way by Manning Publications Co. for review while it still being fresh off the press. So 1st thing – thanks to Manning for this opportunity and a free copy of this must have on every C# developer’s desk book! Several hours ago I finished reading this book (well, except a for a large portion of its quite lengthy appendix). I jumped writing this review right away while still being full of emotions and impressions from reading it thoroughly and running code examples. Before I go any further I would like say that I used to program on various platforms using various languages starting with the Mainframe and ending on Windows, and I gradually shifted toward dealing with databases more than anything, however it happened with me to program in C# 1 a lot when it was first released and then some C# 2 with a big leap in between to C# 5. So my perception and experience reading this book may differ from yours. Also what I want to tell is somewhat funny that back then, knowing some Java and seeing C# 1 released, initially made me drawing a parallel that it is a copycat language, how wrong was I… Interestingly, Jon programs in Java full time, but how little it was mentioned in the book! So more on the book: Be informed, this is not a typical “Recipes”, “Cookbook” or any set of ready solutions, it is rather targeting mature, advanced developers who do not only know how to use a number of features, but are willing to understand how the language is operating “under the hood”. I must state immediately, at the same time I am glad the author did not go into the murky depths of the MSIL, so this is a very welcome decision on covering a modern language as C# for me, thank you Jon! Frankly, not all was that rosy regarding the tone and structure of the book, especially the the first half or so filled me with several negative and positive emotions overpowering each other. To expand more on that, some statements in the book appeared to be bias to me, or filled with pre-justice, it started to look like it had some PR-sole in it, but thankfully this was all gone toward the end of the 1st third of the book. Specifically, the mention on the C# language popularity, Java is the #1 language as per https://sites.google.com/site/pydatalog/pypl/PyPL-PopularitY-of-Programming-Language (many other sources put C at the top which I highly doubt), also many interesting functional languages as Clojure and Groovy appeared and gained huge traction which run on top of Java/JVM whereas C# does not enjoy such a situation. If we want to discuss the popularity in general and say how fast a developer can find a new job that pays well it would be indeed the very Java, C++ or PHP, never C#. Or that phrase on language preference as a personal issue? We choose where to work or we are chosen because of a technology used at a given software shop, not vice versa. The book though it technically very accurate with valid code, concise examples, but I wish the author would give more concrete, real-life examples on where each feature should be used, not how. Another point to realize before you get the book is that it is almost a live book which started to be written when even C# 3 wasn’t around so a lot of ground is covered (nearly half of the book) on the pre-C# 3 feature releases so if you already have a solid background in the previous releases and do not plan to upgrade, perhaps half of the book can be skipped, otherwise this book is surely highly recommended. Alas, for me it was a hard read, most of it. It was not boring (well, only may be two times), it was just hard to grasp some concepts, but do not get me wrong, it did made me pause, on several occasions, and made me read and re-read a page or two. At times I even wondered if I have any IQ at all (LOL). Be prepared to read A LOT on generics, not that they are widely used in the field (I happen to work as a consultant and went thru a lot of code at many places) I can tell my impression is the developers today in best case program using examples found at OpenStack.com. Also unlike the Java world where having the most recent version is nearly mandated by the OSS most companies on the Microsoft platform almost never tempted to upgrade the .Net version very soon and very often. As a side note, I was glad to see code recently that included a nullable variable (myvariable? notation) and this made me smile, besides, I recommended that person this book to expand her knowledge. The good things about this book is that Jon maintains an active forum, prepared code snippets and even a small program (Snippy) that is happy to run the sample code saving you from writing any plumbing code. A tad now on the C# language itself – it sure enjoyed a wonderful road toward perfection and a very high adoption, especially for ASP development. But to me all the recent features that made this statically typed language more dynamic look strange. Don’t we have F#? Which supposed to be the dynamic language? Why do we need to have a hybrid language? Now the developers live their lives in dualism of the static and dynamic variables! And LINQ to SQL, it is covered in depth, but wasn’t it supposed to be dropped? Also it seems that very little is being added, and at a slower pace, e.g. Roslyn will come in late 2014 perhaps, and will be probably the only main feature. Again, it is quite hard to read this book as various chapters, C# versions mentioned every so often only if I only could remember what was covered exactly where! So the fact it has so many jumps/links back and forth I recommend the ebook format to make the navigations easier to perform and I do recommend using software that allows bookmarking, also make sure you have access to plenty of coffee and pizza (hey, you probably know this joke – who a programmer is) ! In terms of closing, if you stuck at C# 1 or 2 level, it is time to embrace the power of C# 5! Finally, to compliment Manning, this book unlike from any other publisher so far, was the only one as well readable (put it formatted) on my tablet as in Adobe Reader on a laptop.

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• Using delegates in C# (Part 2)

  - by rajbk

  Part 1 of this post can be read here. We are now about to see the different syntaxes for invoking a delegate and some c# syntactic sugar which allows you to code faster. We have the following console application. 1: public delegate double Operation(double x, double y); 2:  3: public class Program 4: { 5: [STAThread] 6: static void Main(string[] args) 7: { 8: Operation op1 = new Operation(Division); 9: double result = op1.Invoke(10, 5); 10: 11: Console.WriteLine(result); 12: Console.ReadLine(); 13: } 14: 15: static double Division(double x, double y) { 16: return x / y; 17: } 18: } Line 1 defines a delegate type called Operation with input parameters (double x, double y) and a return type of double. On Line 8, we create an instance of this delegate and set the target to be a static method called Division (Line 15) On Line 9, we invoke the delegate (one entry in the invocation list). The program outputs 5 when run. The language provides shortcuts for creating a delegate and invoking it (see line 9 and 11). Line 9 is a syntactical shortcut for creating an instance of the Delegate. The C# compiler will infer on its own what the delegate type is and produces intermediate language that creates a new instance of that delegate. Line 11 uses a a syntactical shortcut for invoking the delegate by removing the Invoke method. The compiler sees the line and generates intermediate language which invokes the delegate. When this code is compiled, the generated IL will look exactly like the IL of the compiled code above. 1: public delegate double Operation(double x, double y); 2:  3: public class Program 4: { 5: [STAThread] 6: static void Main(string[] args) 7: { 8: //shortcut constructor syntax 9: Operation op1 = Division; 10: //shortcut invoke syntax 11: double result = op1(10, 2); 12: 13: Console.WriteLine(result); 14: Console.ReadLine(); 15: } 16: 17: static double Division(double x, double y) { 18: return x / y; 19: } 20: } C# 2.0 introduced Anonymous Methods. Anonymous methods avoid the need to create a separate method that contains the same signature as the delegate type. Instead you write the method body in-line. There is an interesting fact about Anonymous methods and closures which won’t be covered here. Use your favorite search engine ;-)We rewrite our code to use anonymous methods (see line 9): 1: public delegate double Operation(double x, double y); 2:  3: public class Program 4: { 5: [STAThread] 6: static void Main(string[] args) 7: { 8: //Anonymous method 9: Operation op1 = delegate(double x, double y) { 10: return x / y; 11: }; 12: double result = op1(10, 2); 13: 14: Console.WriteLine(result); 15: Console.ReadLine(); 16: } 17: 18: static double Division(double x, double y) { 19: return x / y; 20: } 21: } We could rewrite our delegate to be of a generic type like so (see line 2 and line 9). You will see why soon. 1: //Generic delegate 2: public delegate T Operation<T>(T x, T y); 3:  4: public class Program 5: { 6: [STAThread] 7: static void Main(string[] args) 8: { 9: Operation<double> op1 = delegate(double x, double y) { 10: return x / y; 11: }; 12: double result = op1(10, 2); 13: 14: Console.WriteLine(result); 15: Console.ReadLine(); 16: } 17: 18: static double Division(double x, double y) { 19: return x / y; 20: } 21: } The .NET 3.5 framework introduced a whole set of predefined delegates for us including public delegate TResult Func<T1, T2, TResult>(T1 arg1, T2 arg2); Our code can be modified to use this delegate instead of the one we declared. Our delegate declaration has been removed and line 7 has been changed to use the Func delegate type. 1: public class Program 2: { 3: [STAThread] 4: static void Main(string[] args) 5: { 6: //Func is a delegate defined in the .NET 3.5 framework 7: Func<double, double, double> op1 = delegate (double x, double y) { 8: return x / y; 9: }; 10: double result = op1(10, 2); 11: 12: Console.WriteLine(result); 13: Console.ReadLine(); 14: } 15: 16: static double Division(double x, double y) { 17: return x / y; 18: } 19: } .NET 3.5 also introduced lambda expressions. A lambda expression is an anonymous function that can contain expressions and statements, and can be used to create delegates or expression tree types. We change our code to use lambda expressions. 1: public class Program 2: { 3: [STAThread] 4: static void Main(string[] args) 5: { 6: //lambda expression 7: Func<double, double, double> op1 = (x, y) => x / y; 8: double result = op1(10, 2); 9: 10: Console.WriteLine(result); 11: Console.ReadLine(); 12: } 13: 14: static double Division(double x, double y) { 15: return x / y; 16: } 17: } C# 3.0 introduced the keyword var (implicitly typed local variable) where the type of the variable is inferred based on the type of the associated initializer expression. We can rewrite our code to use var as shown below (line 7).  The implicitly typed local variable op1 is inferred to be a delegate of type Func<double, double, double> at compile time. 1: public class Program 2: { 3: [STAThread] 4: static void Main(string[] args) 5: { 6: //implicitly typed local variable 7: var op1 = (x, y) => x / y; 8: double result = op1(10, 2); 9: 10: Console.WriteLine(result); 11: Console.ReadLine(); 12: } 13: 14: static double Division(double x, double y) { 15: return x / y; 16: } 17: } You have seen how we can write code in fewer lines by using a combination of the Func delegate type, implicitly typed local variables and lambda expressions.

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• What is SharePoint Out of the Box?

  - by Bil Simser

  It’s always fun in the blog-o-sphere and SharePoint bloggers always keep the pot boiling. Bjorn Furuknap recently posted a blog entry titled Why Out-of-the-Box Makes No Sense in SharePoint, quickly followed up by a rebuttal by Marc Anderson on his blog. Okay, now that we have all the players and the stage what’s the big deal? Bjorn started his post saying that you don’t use “out-of-the-box” (OOTB) SharePoint because it makes no sense. I have to disagree with his premise because what he calls OOTB is basically installing SharePoint and admiring it, but not using it. In his post he lays claim that modifying say the OOTB contacts list by removing (or I suppose adding) a column, now puts you in a situation where you’re no longer using the OOTB functionality. Really? Side note. Dear Internet, please stop comparing building software to building houses. Or comparing software architecture to building architecture. Or comparing web sites to making dinner. Are you trying to dumb down something so the general masses understand it? Comparing a technical skill to a construction operation isn’t the way to do this. Last time I checked, most people don’t know how to build houses and last time I checked people reading technical SharePoint blogs are generally technical people that understand the terms you use. Putting metaphors around software development to make it easy to understand is detrimental to the goal. </rant> Okay, where were we? Right, adding columns to lists means you are no longer using the OOTB functionality. Yeah, I still don’t get it. Another statement Bjorn makes is that using the OOTB functionality kills the flexibility SharePoint has in creating exactly what you want. IMHO this really flies in the absolute face of *where* SharePoint *really* shines. For the past year or so I’ve been leaning more and more towards OOTB solutions over custom development for the simple reason that its expensive to maintain systems and code and assets. SharePoint has enabled me to do this simply by providing the tools where I can give users what they need without cracking open up Visual Studio. This might be the fact that my day job is with a regulated company and there’s more scrutiny with spending money on anything new, but frankly that should be the position of any responsible developer, architect, manager, or PM. Do you really want to throw money away because some developer tells you that you need a custom web part when perhaps with some creative thinking or expectation setting with customers you can meet the need with what you already have. The way I read Bjorn’s terminology of “out-of-the-box” is install the software and tell people to go to a website and admire the OOTB system, but don’t change it! For those that know things like WordPress, DotNetNuke, SubText, Drupal or any of those content management/blogging systems, its akin to installing the software and setting up the “Hello World” blog post or page, then staring at it like it’s useful. “Yes, we are using WordPress!”. Then not adding a new post, creating a new category, or adding an About page. Perhaps I’m wrong in my interpretation. This leads us to what is OOTB SharePoint? To many people I’ve talked to the last few hours on twitter, email, etc. it is *not* just installing software but actually using it as it was fit for purpose. What’s the purpose of SharePoint then? It has many purposes, but using the OOTB templates Microsoft has given you the ability to collaborate on projects, author/share/publish documents, create pages, track items/contacts/tasks/etc. in a multi-user web based interface, and so on. Microsoft has pretty clear definitions of these different levels of SharePoint we’re talking about and I think it’s important for everyone to know what they are and what they mean. Personalization and Administration To me, this is the OOTB experience. You install the product and then are able to do things like create new lists, sites, edit and personalize pages, create new views, etc. Basically use the platform services available to you with Windows SharePoint Services (or SharePoint Foundation in 2010) to your full advantage. No code, no special tools needed, and very little user training required. Could you take someone who has never done anything in a website or piece of software and unleash them onto a site? Probably not. However I would argue that anyone who’s configured the Outlook reading layout or applied styles to a Word document probably won’t have too much difficulty in using SharePoint OUT OF THE BOX. Customization Here’s where things might get a bit murky but to me this is where you start looking at HTML/ASPX page code through SharePoint Designer, using jQuery scripts and plugging them into Web Part Pages via a Content Editor Web Part, and generally enhancing the site. The JavaScript debate might kick in here claiming it’s no different than C#, and frankly you can totally screw a site up with jQuery on a CEWP just as easily as you can with a C# delegate control deployed to the server file system. However (again, my blog, my opinion) the customization label comes in when I need to access the server (for example creating a custom theme) or have some kind of net-new element I add to the system that wasn’t there OOTB. It’s not content (like a new list or site), it’s code and does something functional. Development Here’s were the propeller hats come on and we’re talking algorithms and unit tests and compilers oh my. Software is deployed to the server, people are writing solutions after some kind of training (perhaps), there might be some specialized tools they use to craft and deploy the solutions, there’s the possibility of exceptions being thrown, etc. There are a lot of definitions here and just like customization it might get murky (do you let non-developers build solutions using development, i.e. jQuery/C#?). In my experience, it’s much more cost effective keeping solutions under the first two umbrellas than leaping into the third one. Arguably you could say that you can’t build useful solutions without *some* kind of code (even just some simple jQuery). I think you can get a *lot* of value just from using the OOTB experience and I don’t think you’re constraining your users that much. I’m not saying Marc or Bjorn are wrong. Like Obi-Wan stated, they’re both correct “from a certain point of view”. To me, SharePoint Out of the Box makes total sense and should not be dismissed. I just don’t agree with the premise that Bjorn is basing his statements on but that’s just my opinion and his is different and never the twain shall meet.

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