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• C - What is the proper format to allow a function to show an error was encountered?

  - by BrainSteel

  I have a question about what a function should do if the arguments to said function don't line up quite right, through no fault of the function call. Since that sentence doesn't make much sense, I'll offer my current issue. To keep it simple, here is the most relevant and basic function I have. float getYValueAt(float x, PHYS_Line line, unsigned short* error) *error = 0; if(x < line.start.x || x > line.end.x){ *error = 1; return -1; } if(line.slope.value != 0){ //line's equation: y - line.start.y = line.slope.value(x - line.start.x) return line.slope.value * (x - line.start.x) + line.start.y; } else if(line.slope.denom == 0){ if(line.start.x == x) return line.start.y; else{ *error = 1; return -1; } } else if(line.slope.num == 0){ return line.start.y; } } The function attempts to find the point on a line, given a certain x value. However, under some circumstances, this may not be possible. For example, on the line x = 3, if 5 is passed as a value, we would have a problem. Another problem arises if the chosen x value is not within the interval the line is on. For this, I included the error pointer. Given this format, a function call could work as follows: void foo(PHYS_Line some_line){ unsigned short error = 0; float y = getYValueAt(5, some_line, &error); if(error) fooey(); else do_something_with_y(y); } My question pertains to the error. Note that the value returned is allowed to be negative. Returning -1 does not ensure that an error has occurred. I know that it is sometimes preferred to use the following method to track an error: float* getYValueAt(float x, PHYS_Line line); and then return NULL if an error occurs, but I believe this requires dynamic memory allocation, which seems even less sightly than the solution I was using. So, what is standard practice for an error occurring?

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• Directly Jump to another C++ function

  - by maligree

  I'm porting a small academic OS from TriCore to ARM Cortex (Thumb-2 instruction set). For the scheduler to work, I sometimes need to JUMP directly to another function without modifying the stack nor the link register. On TriCore (or, rather, on tricore-g++), this wrapper template (for any three-argument-function) works: template< class A1, class A2, class A3 > inline void __attribute__((always_inline)) JUMP3( void (*func)( A1, A2, A3), A1 a1, A2 a2, A3 a3 ) { typedef void (* __attribute__((interrupt_handler)) Jump3)( A1, A2, A3); ( (Jump3)func )( a1, a2, a3 ); } //example for using the template: JUMP3( superDispatch, this, me, next ); This would generate the assembler instruction J (a.k.a. JUMP) instead of CALL, leaving the stack and CSAs unchanged when jumping to the (otherwise normal) C++ function superDispatch(SchedulerImplementation* obj, Task::Id from, Task::Id to). Now I need an equivalent behaviour on ARM Cortex (or, rather, for arm-none-linux-gnueabi-g++), i.e. generate a B (a.k.a. BRANCH) instruction instead of BLX (a.k.a. BRANCH with link and exchange). But there is no interrupt_handler attribute for arm-g++ and I could not find any equivalent attribute. So I tried to resort to asm volatile and writing the asm code directly: template< class A1, class A2, class A3 > inline void __attribute__((always_inline)) JUMP3( void (*func)( A1, A2, A3), A1 a1, A2 a2, A3 a3 ) { asm volatile ( "mov.w r0, %1;" "mov.w r1, %2;" "mov.w r2, %3;" "b %0;" : : "r"(func), "r"(a1), "r"(a2), "r"(a3) : "r0", "r1", "r2" ); } So far, so good, in my theory, at least. Thumb-2 requires function arguments to be passed in the registers, i.e. r0..r2 in this case, so it should work. But then the linker dies with undefined reference to `r6' on the closing bracket of the asm statement ... and I don't know what to make of it. OK, I'm not the expert in C++, and the asm syntax is not very straightforward... so has anybody got a hint for me? A hint to the correct __attribute__ for arm-g++ would be one way, a hint to fix the asm code would be another. Another way maybe would be to tell the compiler that a1..a3 should already be in the registers r0..r2 when the asm statement is entered (I looked into that a bit, but did not find any hint).

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• JAVA: XML parsers gives null element

  - by Johan

  When I try to parse a XML-file, it gives sometimes a null element by the title. I think it has to do with HTML-tags &#039; How can I solve this problem? I have the follow XML-file: <item> <title>&#039; Nieuwe DVD &#039;</title> <description>tekst, tekst tekst</description> <link>dvd.html</link> <category>nieuws</category> <pubDate>Sat, 1 Jan 2011 9:24:00 +0000</pubDate> </item> And the follow code to parse the xml-file: //DocumentBuilderFactory, DocumentBuilder are used for //xml parsing DocumentBuilderFactory dbf = DocumentBuilderFactory .newInstance(); DocumentBuilder db = dbf.newDocumentBuilder(); //using db (Document Builder) parse xml data and assign //it to Element Document document = db.parse(is); Element element = document.getDocumentElement(); //take rss nodes to NodeList element.normalize(); NodeList nodeList = element.getElementsByTagName("item"); if (nodeList.getLength() > 0) { for (int i = 0; i < nodeList.getLength(); i++) { //take each entry (corresponds to <item></item> tags in //xml data Element entry = (Element) nodeList.item(i); entry.normalize(); Element _titleE = (Element) entry.getElementsByTagName( "title").item(0); Element _categoryE = (Element) entry .getElementsByTagName("category").item(0); Element _pubDateE = (Element) entry .getElementsByTagName("pubDate").item(0); Element _linkE = (Element) entry.getElementsByTagName( "link").item(0); String _title = _titleE.getFirstChild().getNodeValue(); String _category = _categoryE.getFirstChild().getNodeValue(); Date _pubDate = new Date(_pubDateE.getFirstChild().getNodeValue()); String _link = _linkE.getFirstChild().getNodeValue(); //create RssItemObject and add it to the ArrayList RssItem rssItem = new RssItem(_title, _category, _pubDate, _link); rssItems.add(rssItem); conn.disconnect(); }

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• Browsers (IE and Firefox) freeze when copying large amount of text

  - by Matt

  I have a web application - a Java servlet - that delivers data to users in the form of a text printout in a browser (text marked up with HTML in order to display in the browser as we want it to). The text does display in different colors, though most of it is black. One typical mode of operation is this: 1. User submits a form to request data. 2. Servlet delivers HTML file to browser. 3. User does CTRL+A to select all the text. 4. User does CTRL+C to copy all the text. 5. User goes to a text editor and does CTRL+V to paste the text. In the testing where I'm having this problem, step #2 successfully loads all the data - we wait for that to complete. We can scroll down to the end of what the browser loaded and see the end of the data. However, the browser freezes on step #3 (Firefox) or on step #4 (IE). Because step #2 finishes, I think it is a browser/memory issue, and not an issue with the web application. If I run queries to deliver smaller amounts of data (but after several queries we get the same data we would have above in one query) and copy/paste this text, the file I save it into ends up being about 8 MB. If I save the browser's displayed HTML to a file on my computer via File-Save As from the browser menu, it works fine and the file is about 22 MB. We've tried this on 2 different computers at work (both running Windows XP, with at least 2 GB of RAM and many GB of free disk space), using Firefox and IE. We also tried it on a home computer from a home network outside of work (thinking it might be our IT security software causing the problem), running Windows 7 using IE, and still had the problem. When I've done this, I can see whatever browser I'm using utilizing the CPU at 50%. Firefox's memory usage grows to about 1 GB; IE's stays in the several hundred MBs. We once let this run for half an hour, and it did not complete. I'm most likely going to modify the web app to have an option of delivering a plain text file for download, and I imagine that will get the users what they need. But for the mean time, and because I'm curious - and I don't like my application freezing people's browsers, does anyone have any ideas about the browser freezing? I understand that sometimes you just reach your memory limit, but 22 MB sounds to me like an amount I should be able to copy to the clipboard.

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• Haskell Add Function Return to List Until Certain Length

  - by kienjakenobi

  I want to write a function which takes a list and constructs a subset of that list of a certain length based on the output of a function. If I were simply interested in the first 50 elements of the sorted list xs, then I would use fst (splitAt 50 (sort xs)). However, the problem is that elements in my list rely on other elements in the same list. If I choose element p, then I MUST also choose elements q and r, even if they are not in the first 50 elements of my list. I am using a function finderFunc which takes an element a from the list xs and returns a list with the element a and all of its required elements. finderFunc works fine. Now, the challenge is to write a function which builds a list whose total length is 50 based on multiple outputs of finderFunc. Here is my attempt at this: finish :: [a] -> [a] -> [a] --This is the base case, which adds nothing to the final list finish [] fs = [] --The function is recursive, so the fs variable is necessary so that finish -- can forward the incomplete list to itself. finish ps fs -- If the final list fs is too small, add elements to it | length fs < 50 && length (fs ++ newrs) <= 50 = fs ++ finish newps newrs -- If the length is met, then add nothing to the list and quit | length fs >= 50 = finish [] fs -- These guard statements are currently lacking, not the main problem | otherwise = finish [] fs where --Sort the candidate list sortedps = sort ps --(finderFunc a) returns a list of type [a] containing a and all the -- elements which are required to go with it. This is the interesting -- bit. rs is also a subset of the candidate list ps. rs = finderFunc (head sortedps) --Remove those elements which are already in the final list, because -- there can be overlap newrs = filter (`notElem` fs) rs --Remove the elements we will add to the list from the new list -- of candidates newps = filter (`notElem` rs) ps I realize that the above if statements will, in some cases, not give me a list of exactly 50 elements. This is not the main problem, right now. The problem is that my function finish does not work at all as I would expect it to. Not only does it produce duplicate elements in the output list, but it sometimes goes far above the total number of elements I want to have in the list. The way this is written, I usually call it with an empty list, such as: finish xs [], so that the list it builds on starts as an empty list.

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• How can I link two Java serialised objects back together?

  - by Kidburla

  Sometimes (quite a lot, actually) we get a situation in Java where two objects are pointing to the same thing. Now if we serialise these separately it is quite appropriate that the serialised forms have separate copies of the object as it should be possible to open one without the other. However if we now deserialise them both, we find that they are still separated. Is there any way to link them back together? Example follows. public class Example { private static class ContainerClass implements java.io.Serializable { private ReferencedClass obj; public ReferencedClass get() { return obj; } public void set(ReferencedClass obj) { this.obj = obj; } } private static class ReferencedClass implements java.io.Serializable { private int i = 0; public int get() { return i; } public void set(int i) { this.i = i; } } public static void main(String[] args) throws Exception { //Initialise the classes ContainerClass test1 = new ContainerClass(); ContainerClass test2 = new ContainerClass(); ReferencedClass ref = new ReferencedClass(); //Make both container class point to the same reference test1.set(ref); test2.set(ref); //This does what we expect: setting the integer in one (way of accessing the) referenced class sets it in the other one test1.get().set(1234); System.out.println(Integer.toString(test2.get().get())); //Now serialise the container classes java.io.ObjectOutputStream os = new java.io.ObjectOutputStream(new java.io.FileOutputStream("C:\\Users\\Public\\test1.ser")); os.writeObject(test1); os.close(); os = new java.io.ObjectOutputStream(new java.io.FileOutputStream("C:\\Users\\Public\\test2.ser")); os.writeObject(test2); os.close(); //And deserialise them java.io.ObjectInputStream is = new java.io.ObjectInputStream(new java.io.FileInputStream("C:\\Users\\Public\\test1.ser")); ContainerClass test3 = (ContainerClass)is.readObject(); is.close(); is = new java.io.ObjectInputStream(new java.io.FileInputStream("C:\\Users\\Public\\test2.ser")); ContainerClass test4 = (ContainerClass)is.readObject(); is.close(); //We expect the same thing as before, and would expect a result of 4321, but this doesn't happen as the referenced objects are now separate instances test3.get().set(4321); System.out.println(Integer.toString(test4.get().get())); } }

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• new operator overwriting an existing object

  - by dvpdiner2

  I have a custom FastStack class, implemented as a fixed size array and an index into that array. In my copy constructor, I allocate the array and then assign each object from the copy's array into the new array. There's some refcounting in the objects on the stack, hence assignment is used rather than a simple copy. The problem is that when allocating the array, it sometimes overwrites part of the other stack's array. As can be expected, this leads to eventual segmentation faults when that data is dereferenced. class FastStack { private: int m_size, m_ptr; ObjectRef* m_stack; public: FastStack(int size) : m_size(size), m_ptr(-1) { m_stack = new ObjectRef[m_size]; } FastStack(const FastStack& copy) : m_size(copy.m_size), m_ptr(copy.m_ptr) { long a = (long)copy.m_stack[0]; m_stack = new ObjectRef[m_size]; if ((long)copy.m_stack[0] != a) fprintf(stderr, "\nWe have a serious problem!\n\n"); for (int i = 0; i <= m_ptr; i++) m_stack[i] = copy.m_stack[i]; } ~FastStack() { delete[] m_stack; } }; class ObjectRef { private: DataObj* m_obj; public: ObjectRef() : m_obj(0) { } ObjectRef(DataObj* obj) : m_obj(obj) { if (m_obj) m_obj->addRef(); } ObjectRef(const ObjectRef& obj) : m_obj(obj.m_obj) { if (m_obj) m_obj->addRef(); } ~ObjectRef() { if (m_obj) m_obj->delRef(); } ObjectRef& operator=(DataObj* obj) { if (obj) obj->addRef(); if (m_obj) m_obj->delRef(); m_obj = obj; return *this; } ObjectRef& operator=(const ObjectRef& obj) { if (obj.m_obj) obj.m_obj->addRef(); if (m_obj) m_obj->delRef(); m_obj = obj.m_obj; return *this; } }; I see that "We have a serious problem!" line shortly before a segfault, and stepping through it with gdb I can see that one of the ObjectRefs created by new has the same address as the other stack's array. My first instinct is to say that new should never be allocating memory that is already in use, but that clearly seems to be the case here and I am at a complete loss as to what can be done. Added: At the time that I see this happen, m_size = 2 and m_ptr = 0.

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• Socket connection to a telnet-based server hangs on read

  - by mixwhit

  I'm trying to write a simple socket-based client in Python that will connect to a telnet server. I can test the server by telnetting to its port (5007), and entering text. It responds with a NAK (error) or an AK (success), sometimes accompanied by other text. Seems very simple. I wrote a client to connect and communicate with the server, but it hangs on the first attempt to read the response. The connection is successful. Queries like getsockname and getpeername are successful. The send command returns a value that equals the number of characters I'm sending, so it seems to be sending correctly. But in the end, it always hangs when I try to read the response. I've tried using both file-based objects like readline and write (via socket.makefile), as well as using send and recv. With the file object I tried making it with "rw" and reading and writing via that object, and later tried one object for "r" and another for "w" to separate them. None of these worked. I used a packet sniffer to watch what's going on. I'm not versed in all that I'm seeing, but during a telnet session I can see my typed text and the server's text coming back. During my Python socket connection, I can see my text going to the server, but packets back don't seem to have any text in them. Any ideas on what I'm doing wrong, or any strategies to try? Here's the code I'm using (in this case, it's with send and recv): #!/usr/bin/python host = "localhost" port = 5007 msg = "HELLO EMC 1 1" msg2 = "HELLO" import socket import sys try: skt = socket.socket(socket.AF_INET, socket.SOCK_STREAM) except socket.error, e: print("Error creating socket: %s" % e) sys.exit(1) try: skt.connect((host,port)) except socket.gaierror, e: print("Address-related error connecting to server: %s" % e) sys.exit(1) except socket.error, e: print("Error connecting to socket: %s" % e) sys.exit(1) try: print(skt.send(msg)) print("SEND: %s" % msg) except socket.error, e: print("Error sending data: %s" % e) sys.exit(1) while 1: try: buf = skt.recv(1024) print("RECV: %s" % buf) except socket.error, e: print("Error receiving data: %s" % e) sys.exit(1) if not len(buf): break sys.stdout.write(buf)

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• File sorting, Comparison method violates its general contract

  - by user2677383

  My file sorting comparator sometimes invoke java.lang.IllegalArgumentException in android app. I cannot figure out the reason. could you explain that? here is my code block: Comparator cc = new Comparator<File>() { @Override public int compare(File f1, File f2) { if (f1.isDirectory() && !f2.isDirectory()) { return 1; } if (f2.isDirectory() && !f1.isDirectory()) { return -1; } if ((f1.isFile() && f2.isFile()) || (f1.isDirectory() && f2.isDirectory())) { if (sort == 1) { return Util.compareFileName(f2.getName(), f1.getName()); } else if (sort == 2) { return (int) (f1.lastModified() - f2.lastModified()); } else if (sort == 3) { return (int) (f2.lastModified() - f1.lastModified()); } else if (sort == 4) { return (int) (f1.length() - f2.length()); } else if (sort == 5) { return (int) (f2.length() - f1.length()); } else return Util.compareFileName(f1.getName(), f2.getName()); } return f1.compareTo(f2); } }; Util.compareFileName is as followings: public static int compareFileName(String s1, String s2) { int thisMarker = 0; int thatMarker = 0; int s1Length = s1.length(); int s2Length = s2.length(); while (thisMarker < s1Length && thatMarker < s2Length) { String thisChunk = getChunk(s1, s1Length, thisMarker); thisMarker += thisChunk.length(); String thatChunk = getChunk(s2, s2Length, thatMarker); thatMarker += thatChunk.length(); // If both chunks contain numeric characters, sort them numerically int result = 0; if (isDigit(thisChunk.charAt(0)) && isDigit(thatChunk.charAt(0))) { // Simple chunk comparison by length. int thisChunkLength = thisChunk.length(); result = thisChunkLength - thatChunk.length(); // If equal, the first different number counts if (result == 0) { for (int i = 0; i < thisChunkLength; i++) { result = thisChunk.charAt(i) - thatChunk.charAt(i); if (result != 0) { return result; } } } } else { result = thisChunk.compareTo(thatChunk); } if (result != 0) return result; } return s1Length - s2Length; }

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• Starting jetty with spring xml as a background process/thread

  - by compass

  My goal is to set up a jetty test server and inject a custom servlet to test some REST classes in my project. I was able to launch the server with spring xml and run tests against that server. The issue I'm having is sometimes after the server started, the process stopped at the point before running the tests. It seems jetty didn't go to background. It works every time on my computer. But when I deployed to my CI server, it doesn't work. It also doesn't work when I'm on VPN. (Strange.) The server should be completed initialized as when the tests stuck, I was able to access the server using a browser. Here is my spring context xml: .... <bean id="servletHolder" class="org.eclipse.jetty.servlet.ServletHolder"> <constructor-arg ref="courseApiServlet"/> </bean> <bean id="servletHandler" class="org.eclipse.jetty.servlet.ServletContextHandler"/> <!-- Adding the servlet holders to the handlers --> <bean id="servletHandlerSetter" class="org.springframework.beans.factory.config.MethodInvokingFactoryBean"> <property name="targetObject" ref="servletHandler"/> <property name="targetMethod" value="addServlet"/> <property name="arguments"> <list> <ref bean="servletHolder"/> <value>/*</value> </list> </property> </bean> <bean id="httpTestServer" class="org.eclipse.jetty.server.Server" init-method="start" destroy-method="stop" depends-on="servletHandlerSetter"> <property name="connectors"> <list> <bean class="org.eclipse.jetty.server.nio.SelectChannelConnector"> <property name="port" value="#{settings['webservice.server.port']}" /> </bean> </list> </property> <property name="handler"> <ref bean="servletHandler" /> </property> </bean> Running latest Jetty 8.1.8 server and Spring 3.1.3. Any idea?

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• Is it thread safe to read a form controls value (but not change it) without using Invoke/BeginInvoke from another thread

  - by goku_da_master

  I know you can read a gui control from a worker thread without using Invoke/BeginInvoke because my app is doing it now. The cross thread exception error is not being thrown and my System.Timers.Timer thread is able to read gui control values just fine (unlike this guy: can a worker thread read a control in the GUI?) Question 1: Given the cardinal rule of threads, should I be using Invoke/BeginInvoke to read form control values? And does this make it more thread-safe? The background to this question stems from a problem my app is having. It seems to randomly corrupt form controls another thread is referencing. (see question 2) Question 2: I have a second thread that needs to update form control values so I Invoke/BeginInvoke to update those values. Well this same thread needs a reference to those controls so it can update them. It holds a list of these controls (say DataGridViewRow objects). Sometimes (not always), the DataGridViewRow reference gets "corrupt". What I mean by corrupt, is the reference is still valid, but some of the DataGridViewRow properties are null (ex: row.Cells). Is this caused by question 1 or can you give me any tips on why this might be happening? Here's some code (the last line has the problem): public partial class MyForm : Form { void Timer_Elapsed(object sender) { // we're on a new thread (this function gets called every few seconds) UpdateUiHelper updateUiHelper = new UpdateUiHelper(this); foreach (DataGridViewRow row in dataGridView1.Rows) { object[] values = GetValuesFromDb(); updateUiHelper.UpdateRowValues(row, values[0]); } // .. do other work here updateUiHelper.UpdateUi(); } } public class UpdateUiHelper { private readonly Form _form; private Dictionary<DataGridViewRow, object> _rows; private delegate void RowDelegate(DataGridViewRow row); private readonly object _lockObject = new object(); public UpdateUiHelper(Form form) { _form = form; _rows = new Dictionary<DataGridViewRow, object>(); } public void UpdateRowValues(DataGridViewRow row, object value) { if (_rows.ContainsKey(row)) _rows[row] = value; else { lock (_lockObject) { _rows.Add(row, value); } } } public void UpdateUi() { foreach (DataGridViewRow row in _rows.Keys) { SetRowValueThreadSafe(row); } } private void SetRowValueThreadSafe(DataGridViewRow row) { if (_form.InvokeRequired) { _form.Invoke(new RowDelegate(SetRowValueThreadSafe), new object[] { row }); return; } // now we're on the UI thread object newValue = _rows[row]; row.Cells[0].Value = newValue; // randomly errors here with NullReferenceException, but row is never null! }

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• Where can I find "canonical" sample programs that give quick refreshers for any given language? [on hold]

  - by acheong87

  Note to those close-voting this question: I understand this isn't a conventional programming question and I can agree with the reasoning that it's in the subjective domain (like best-of lists). In other ways though I think it's appropriate because, though it's not a "a specific programming problem," nor concerning "a software algorithm", nor (strictly) concerning "software tools commonly used by programmers", I think it is a "practical, answerable [problem that is] unique to the programming profession," and I think it is "based on an actual [problem I] face." I've been wanting this for some time now, because both approaches of (a) Googling for samples as I write every other line of code and (b) just winging it and seeing what errors crop up, distract me from coding efficiently. This note will be removed if the question gains popularity; this question will be deleted otherwise. I spend most of my time developing in C++, PHP, or Javascript, and every once in a while I have to do something in, say, VBA. In those times, it'd be convenient if I could just put up some sample code on a second monitor, something in between a cheat sheet (often too compact; and doesn't resemble anything that could actually compile/run), and a language reference (often too verbose, or segmented; requires extra steps to search or click through an index), so I can just glance at it and recall things, like how to loop through non-empty cells in a column. I think there's a hidden benefit to seeing formed code, that triggers the right spots in our brains to get back into a language we only need to brush up on. Similar in spirit is how http://ideone.com lets you click "Template" in any given language so you can get started without even doing a search. That template alone tells a lot, sometimes! Case-sensitivity, whitespace conventions, identifier conventions, the spelling of certain types, etc. I couldn't find a resource that pulled together such samples, so if there indeed doesn't exist such a repository, I was hoping this question would inspire professionals and experts to contribute links to the most useful sample code they've used for just this purpose: a keep-on-the-side, form-as-well-as-content, compilable/executable, reminder of a language's basic and oft-used features. Personally I am interested in seeing "samplers" for: VBA, Perl, Python, Java, C# (though for some of these autocompleters in Eclipse, Visual Studio, etc. help enough), awk, and sed. I'm tagging c++, php, and javascript because these are languages for which I'd best be able to evaluate whether proffered sample code matches what I had in mind.

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• Pass variables between separate instances of ruby (without writing to a text file or database)

  - by boulder_ruby

  Lets say I'm running a long worker-script in one of several open interactive rails consoles. The script is updating columns in a very, very, very large table of records. I've muted the ActiveRecord logger to speed up the process, and instruct the script to output some record of progress so I know how roughly how long the process is going to take. That is what I am currently doing and it would look something like this: ModelName.all.each_with_index do |r, i| puts i if i % 250 ...runs some process... r.save end Sometimes its two nested arrays running, such that there would be multiple iterators and other things running all at once. Is there a way that I could do something like this and access that variable from a separate rails console? (such that the variable would be overwritten every time the process is run without much slowdown) records = ModelName.all $total = records.count records.each_with_index do |r, i| $i = i ...runs some process... r.save end meanwhile mid-process in other console puts "#{($i/$total * 100).round(2)}% complete" #=> 67.43% complete I know passing global variables from one separate instance of ruby to the next doesn't work. I also just tried this to no effect as well unix console 1 $X=5 echo {$X} #=> 5 unix console 2 echo {$X} #=> "" Lastly, I also know using global variables like this is a major software design pattern no-no. I think that's reasonable, but I'd still like to know how to break that rule if I'd like. Writing to a text file obviously would work. So would writing to a separate database table or something. That's not a bad idea. But the really cool trick would be sharing a variable between two instances without writing to a text file or database column. What would this be called anyway? Tunneling? I don't quite know how to tag this question. Maybe bad-idea is one of them. But honestly design-patterns isn't what this question is about.

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• Load HTML NSString into a UIWebView

  - by ehenrik

  Im doing a project where I connect to a webpage using the NSURLConnection to be able to monitor the status codes that are returned (200 OK / 404 ERROR). I would like to send the user to the top url www.domain.com if I recieve 404 as status code and if i recieve as 200 status code I would like to load the page in to a webview. I have seen several implementations of this problem by creating a new request but I feel that it is unnecessary since you already received the html in the first request so i would just like to load that HTML in to the webView. So i try to use the [webView loadHTMLFromString: baseURL:] but it doesn't always work, I have noticed that when i print the NSString with html in the connectionDidFinnishLoading it sometimes is null and when I monitor these cases by printing the html in didReceiveData a random number of the last packets is NULL (differs between 2-10). It is always the same webpages that doesn't get loaded. If I load them to my webView using [webView loadRequest:myRequest] it always works. My implementation looks like this perhaps someone of you can see what Im doing wrong. I create my first request with a button click. -(IBAction)buttonClick:(id)sender { NSURL *url = [NSURL URLWithString:@"http://www.domain.com/page2/apa.html"]; NSURLRequest *theRequest = [NSURLRequest requestWithURL:url] NSURLConnection *theConnection = [[NSURLConnection alloc] initWithRequest:theRequest delegate:self]; if( theConnection ) { webData = [[NSMutableData data] retain]; } else { } } Then I monitor the response code in the didReceiveResponse method by casting the request to a NSHTTPURLResponse to be able to access the status codes and then setting a Bool depending on the status code. -(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response { NSHTTPURLResponse *ne = (NSHTTPURLResponse *)response; if ([ne statusCode] == 200){ ok = TRUE; } [webData setLength: 0]; } I then check the bools value in connectionDidFinnishLoading. If I log the html NSString I get the source of the webpage so i know that it isn't an empty string. -(void)connectionDidFinishLoading:(NSURLConnection *)connection { NSString *html = [[NSString alloc] initWithBytes: [webData mutableBytes] length:[webData length] encoding:NSUTF8StringEncoding]; NSURL *url = [NSURL URLWithString:@"http://www.domain.com/"]; if (ok){ [webView loadHTMLString:html baseURL:url]; ok = FALSE; } else{ //Create a new request to www.domain.com } } webData is an instance variable and I load it in didReceiveData like this. -(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data { [webData appendData:data]; }

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• Boost MultiIndex - objects or pointers (and how to use them?)?

  - by Sarah

  I'm programming an agent-based simulation and have decided that Boost's MultiIndex is probably the most efficient container for my agents. I'm not a professional programmer, and my background is very spotty. I've two questions: Is it better to have the container contain the agents (of class Host) themselves, or is it more efficient for the container to hold Host *? Hosts will sometimes be deleted from memory (that's my plan, anyway... need to read up on new and delete). Hosts' private variables will get updated occasionally, which I hope to do through the modify function in MultiIndex. There will be no other copies of Hosts in the simulation, i.e., they will not be used in any other containers. If I use pointers to Hosts, how do I set up the key extraction properly? My code below doesn't compile. // main.cpp - ATTEMPTED POINTER VERSION ... #include <boost/multi_index_container.hpp> #include <boost/multi_index/hashed_index.hpp> #include <boost/multi_index/member.hpp> #include <boost/multi_index/ordered_index.hpp> #include <boost/multi_index/mem_fun.hpp> #include <boost/tokenizer.hpp> typedef multi_index_container< Host *, indexed_by< // hash by Host::id hashed_unique< BOOST_MULTI_INDEX_MEM_FUN(Host,int,Host::getID) > // arg errors here > // end indexed_by > HostContainer; ... int main() { ... HostContainer testHosts; Host * newHostPtr; newHostPtr = new Host( t, DOB, idCtr, 0, currentEvents ); testHosts.insert( newHostPtr ); ... } I can't find a precisely analogous example in the Boost documentation, and my knowledge of C++ syntax is still very weak. The code does appear to work when I replace all the pointer references with the class objects themselves. As best I can read it, the Boost documentation (see summary table at bottom) implies I should be able to use member functions with pointer elements.

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• Windows Server: specifying the default IP address when NIC has multiple addresses

  - by Cédric Boivin

  I have a Windows Server which has ~10 IP addresses statically bound. The problem is I don't know how to specify the default IP address. Sometimes when I assign a new address to the NIC, the default IP address changes with the last IP entered in the advanced IP configuration on the NIC. This has the effect (since I use NAT) that the outgoing public IP changes too. Even though this problem is currently on Windows Server 2008, I've had the same problem with a Windows Server 2003. How can you set the default IP address on a NIC when it has multiple IP addresses bound? I remark something. When i check route print i see is it there the problem ? 0.0.0.0 0.0.0.0 192.168.x.x 192.168.99.49 261 if i want the default ip be example : 192.168.99.100 There is my route. Network Destination Netmask Gateway Interface Metric 0.0.0.0 0.0.0.0 192.168.99.1 192.168.99.49 261 10.10.10.0 255.255.255.0 On-link 10.10.10.10 261 10.10.10.10 255.255.255.255 On-link 10.10.10.10 261 10.10.10.255 255.255.255.255 On-link 10.10.10.10 261 192.168.99.0 255.255.255.0 On-link 192.168.99.49 261 192.168.99.49 255.255.255.255 On-link 192.168.99.49 261 192.168.99.51 255.255.255.255 On-link 192.168.99.49 261 192.168.99.52 255.255.255.255 On-link 192.168.99.49 261 192.168.99.53 255.255.255.255 On-link 192.168.99.49 261 192.168.99.54 255.255.255.255 On-link 192.168.99.49 261 192.168.99.55 255.255.255.255 On-link 192.168.99.49 261 192.168.99.56 255.255.255.255 On-link 192.168.99.49 261 192.168.99.57 255.255.255.255 On-link 192.168.99.49 261 192.168.99.58 255.255.255.255 On-link 192.168.99.49 261 192.168.99.59 255.255.255.255 On-link 192.168.99.49 261 192.168.99.60 255.255.255.255 On-link 192.168.99.49 261 192.168.99.61 255.255.255.255 On-link 192.168.99.49 261 192.168.99.62 255.255.255.255 On-link 192.168.99.49 261 192.168.99.64 255.255.255.255 On-link 192.168.99.49 261 192.168.99.65 255.255.255.255 On-link 192.168.99.49 261 192.168.99.66 255.255.255.255 On-link 192.168.99.49 261 192.168.99.67 255.255.255.255 On-link 192.168.99.49 261 192.168.99.68 255.255.255.255 On-link 192.168.99.49 261 192.168.99.70 255.255.255.255 On-link 192.168.99.49 261 192.168.99.71 255.255.255.255 On-link 192.168.99.49 261 192.168.99.100 255.255.255.255 On-link 192.168.99.49 261 192.168.99.108 255.255.255.255 On-link 192.168.99.49 261 192.168.99.109 255.255.255.255 On-link 192.168.99.49 261 192.168.99.112 255.255.255.255 On-link 192.168.99.49 261 192.168.99.255 255.255.255.255 On-link 192.168.99.49 261 224.0.0.0 240.0.0.0 On-link 192.168.99.49 261 224.0.0.0 240.0.0.0 On-link 10.10.10.10 261 255.255.255.255 255.255.255.255 On-link 192.168.99.49 261 255.255.255.255 255.255.255.255 On-link 10.10.10.10 261 I need to be certain, when i go on internet i go with the 192.168.99.100 how i do that ?

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• Windows Server: specifying the default IP address when NIC has multiple addresses

  - by Cédric Boivin

  I have a Windows Server which has ~10 IP addresses statically bound. The problem is I don't know how to specify the default IP address. Sometimes when I assign a new address to the NIC, the default IP address changes with the last IP entered in the advanced IP configuration on the NIC. This has the effect (since I use NAT) that the outgoing public IP changes too. Even though this problem is currently on Windows Server 2008, I've had the same problem with a Windows Server 2003. How can you set the default IP address on a NIC when it has multiple IP addresses bound? I remark something. When i check route print i see is it there the problem ? 0.0.0.0 0.0.0.0 192.168.x.x 192.168.99.49 261 if i want the default ip be example : 192.168.99.100 There is my route. Network Destination Netmask Gateway Interface Metric 0.0.0.0 0.0.0.0 192.168.99.1 192.168.99.49 261 10.10.10.0 255.255.255.0 On-link 10.10.10.10 261 10.10.10.10 255.255.255.255 On-link 10.10.10.10 261 10.10.10.255 255.255.255.255 On-link 10.10.10.10 261 192.168.99.0 255.255.255.0 On-link 192.168.99.49 261 192.168.99.49 255.255.255.255 On-link 192.168.99.49 261 192.168.99.51 255.255.255.255 On-link 192.168.99.49 261 192.168.99.52 255.255.255.255 On-link 192.168.99.49 261 192.168.99.53 255.255.255.255 On-link 192.168.99.49 261 192.168.99.54 255.255.255.255 On-link 192.168.99.49 261 192.168.99.55 255.255.255.255 On-link 192.168.99.49 261 192.168.99.56 255.255.255.255 On-link 192.168.99.49 261 192.168.99.57 255.255.255.255 On-link 192.168.99.49 261 192.168.99.58 255.255.255.255 On-link 192.168.99.49 261 192.168.99.59 255.255.255.255 On-link 192.168.99.49 261 192.168.99.60 255.255.255.255 On-link 192.168.99.49 261 192.168.99.61 255.255.255.255 On-link 192.168.99.49 261 192.168.99.62 255.255.255.255 On-link 192.168.99.49 261 192.168.99.64 255.255.255.255 On-link 192.168.99.49 261 192.168.99.65 255.255.255.255 On-link 192.168.99.49 261 192.168.99.66 255.255.255.255 On-link 192.168.99.49 261 192.168.99.67 255.255.255.255 On-link 192.168.99.49 261 192.168.99.68 255.255.255.255 On-link 192.168.99.49 261 192.168.99.70 255.255.255.255 On-link 192.168.99.49 261 192.168.99.71 255.255.255.255 On-link 192.168.99.49 261 192.168.99.100 255.255.255.255 On-link 192.168.99.49 261 192.168.99.108 255.255.255.255 On-link 192.168.99.49 261 192.168.99.109 255.255.255.255 On-link 192.168.99.49 261 192.168.99.112 255.255.255.255 On-link 192.168.99.49 261 192.168.99.255 255.255.255.255 On-link 192.168.99.49 261 224.0.0.0 240.0.0.0 On-link 192.168.99.49 261 224.0.0.0 240.0.0.0 On-link 10.10.10.10 261 255.255.255.255 255.255.255.255 On-link 192.168.99.49 261 255.255.255.255 255.255.255.255 On-link 10.10.10.10 261 I need to be certain, when i go on internet i go with the 192.168.99.100 how i do that ?

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• SBS 2008 SP2 Backup - Volume Shadow Copy Operation Failed

  - by Robert Ortisi

  Server Setup Exchange 2007 Version: 08.03.0192.001 (Rollup 4) Windows Small Business Server 2008 SP2 (Rollup 5) Exchange set up on D: drive (449 GB / 698 GB Free) 80 GB / 148 GB Free on OS drive. Issue Backup Failure (VSS related) Backup Software Windows Server Backup (ver 1.0) Simplified Error Creation of the shared protection point timed out. Unknown error (0x81000101) The flush and hold writes operation on volume C: timed out while waiting for a release writes command. Volume Shadow Copy Warning: VSS spent 43 seconds trying to flush and hold the volume \?\Volume{b562a5dd-8246-11de-a75b-806e6f6e6963}. This might cause problems when other volumes in the shadow-copy set timeout waiting for the release-writes phase, and it can cause the shadow-copy creation to fail. Trying again when disk activity is lower may solve this problem. What I've tried Server Reboot. Updated Server and Exchange. ReConfigured Sharepoint (Helped resolve last vss error I encountered). registered VSS Dll's (Backups will sometimes work afterwards but VSS writers fail soon after). Tried Implementing Hotfix: http://support.microsoft.com/kb/956136 Tried Implementing Hotfix: http://support.microsoft.com/kb/972135 I left it for a few days and a few backups came through but then began to fail again. Detailed Information Log Name: Application Source: VSS Date: 16/11/2011 8:02:11 PM Event ID: 12341 Task Category: None Level: Warning Keywords: Classic User: N/A Computer: SERVER.DOMAIN.local Description: Volume Shadow Copy Warning: VSS spent 43 seconds trying to flush and hold the volume \?\Volume{b562a5dd-8246-11de-a75b-806e6f6e6963}. This might cause problems when other volumes in the shadow-copy set timeout waiting for the release-writes phase, and it can cause the shadow-copy creation to fail. Trying again when disk activity is lower may solve this problem. Operation: Executing Asynchronous Operation Context: Current State: flush-and-hold writes Volume Name: \?\Volume{b562a5dd-8246-11de-a75b-806e6f6e6963}\ Event Xml: 12341 3 0 0x80000000000000 1651049 Application SERVER.DOMAIN.local 43 \?\Volume{b562a5dd-8246-11de-a75b-806e6f6e6963}\ Operation: Executing Asynchronous Operation Context: Current State: flush-and-hold writes Volume Name: \?\Volume{b562a5dd-8246-11de-a75b-806e6f6e6963}\ ================================================================================= Log Name: System Source: volsnap Date: 16/11/2011 8:02:11 PM Event ID: 8 Task Category: None Level: Error Keywords: Classic User: N/A Computer: SERVER.DOMAIN.local Description: The flush and hold writes operation on volume C: timed out while waiting for a release writes command. Event Xml: 8 2 0 0x80000000000000 987135 System SERVER.DOMAIN.local ================================================================================== Log Name: Application Source: Microsoft-Windows-Backup Date: 16/11/2011 8:11:18 PM Event ID: 521 Task Category: None Level: Error Keywords: User: SYSTEM Computer: SERVER.DOMAIN.local Description: Backup started at '16/11/2011 9:00:35 AM' failed as Volume Shadow copy operation failed for backup volumes with following error code '2155348001'. Please rerun backup once issue is resolved. Event Xml: 521 0 2 0 0 0x8000000000000000 1651065 Application SERVER.DOMAIN.local 2011-11-16T09:00:35.446Z 2155348001 %%2155348001 ================================================================================== Writer name: 'FRS Writer' Writer Id: {d76f5a28-3092-4589-ba48-2958fb88ce29} Writer Instance Id: {ba047fc6-9ce8-44ba-b59f-f2f8c07708aa} State: [5] Waiting for completion Last error: No error Writer name: 'ASR Writer' Writer Id: {be000cbe-11fe-4426-9c58-531aa6355fc4} Writer Instance Id: {0aace3e2-c840-4572-bf49-7fcc3fbcf56d} State: [1] Stable Last error: No error Writer name: 'Shadow Copy Optimization Writer' Writer Id: {4dc3bdd4-ab48-4d07-adb0-3bee2926fd7f} Writer Instance Id: {054593e2-2086-4480-92e5-30386509ed1b} State: [1] Stable Last error: No error Writer name: 'Registry Writer' Writer Id: {afbab4a2-367d-4d15-a586-71dbb18f8485} Writer Instance Id: {840e6f5f-f35a-4b65-bb20-060cf2ee892a} State: [1] Stable Last error: No error Writer name: 'COM+ REGDB Writer' Writer Id: {542da469-d3e1-473c-9f4f-7847f01fc64f} Writer Instance Id: {9486bedc-f6e8-424b-b563-8b849d51b1e1} State: [1] Stable Last error: No error Writer name: 'BITS Writer' Writer Id: {4969d978-be47-48b0-b100-f328f07ac1e0} Writer Instance Id: {29368bb3-e04b-4404-8fc9-e62dae18da91} State: [1] Stable Last error: No error Writer name: 'Dhcp Jet Writer' Writer Id: {be9ac81e-3619-421f-920f-4c6fea9e93ad} Writer Instance Id: {cfb58c78-9609-4133-8fc8-f66b0d25e12d} State: [5] Waiting for completion Last error: No error ==================================================================================

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• Postfix/SMTPD Relay Access Denied when sending outside the network

  - by David

  I asked a very similar question some 4 or 5 months ago, but haven't tracked down a suitable answer. I decided to post a new question so that I can ... a) Post updated info b) post my most current postconf -n output When a user sends mail from inside the network (via webmail) to email addresses both inside and outside the network, the email is delivered. When a user with an email account on the system sends mail from outside the network, using the server as the relay, to addresses inside the network, the email is delivered. But [sometimes] when a user connects via SMTPD to send email to an external address, a Relay Access Denied error is returned: Feb 25 19:33:49 myers postfix/smtpd[8044]: NOQUEUE: reject: RCPT from host-68-169-158-182.WISOLT2.epbfi.com[68.169.158.182]: 554 5.7.1 <host-68-169-158-182.WISOLT2.epbfi.com[68.169.158.182]>: Client host rejected: Access denied; from=<[email protected]> to=<[email protected]> proto=ESMTP helo=<my-computer-name> Feb 25 19:33:52 myers postfix/smtpd[8044]: disconnect from host-68-169-158-182.WISOLT2.epbfi.com[68.169.158.182] Sending this through Microsoft Outlook 2003 generates the above log. However, sending through my iPhone, with the exact same settings, goes through fine: Feb 25 19:37:18 myers postfix/qmgr[3619]: A2D861302C9: from=<[email protected]>, size=1382, nrcpt=1 (queue active) Feb 25 19:37:18 myers amavis[2799]: (02799-09) FWD via SMTP: <[email protected]> -> <[email protected]>,BODY=7BIT 250 2.0.0 Ok, id=02799-09, from MTA([127.0.0.1]:10025): 250 2.0.0 Ok: queued as A2D861302C9 Feb 25 19:37:18 myers amavis[2799]: (02799-09) Passed CLEAN, [68.169.158.182] [68.169.158.182] <[email protected]> -> <[email protected]>, Message-ID: <[email protected]>, mail_id: yMLvzVQJloFV, Hits: -9.607, size: 897, queued_as: A2D861302C9, 6283 ms Feb 25 19:37:18 myers postfix/lmtp[8752]: 2ED3A1302C8: to=<[email protected]>, relay=127.0.0.1[127.0.0.1]:10024, delay=6.6, delays=0.25/0.01/0.19/6.1, dsn=2.0.0, status=sent (250 2.0.0 Ok, id=02799-09, from MTA([127.0.0.1]:10025): 250 2.0.0 Ok: queued as A2D861302C9) Feb 25 19:37:18 myers postfix/qmgr[3619]: 2ED3A1302C8: removed Outgoing Settings on Outlook 2003 match the settings on my iPhone: SMTP server: mail.my-domain.com Username: My full email address Uses SSL Server Port 587 Now, here's postconf -n. I realize the "My Networks" Parameter is a bit nasty. I have these IP addresses in here for just this reason, as others have been complaining of this problem too: alias_database = hash:/etc/postfix/aliases alias_maps = $alias_database append_dot_mydomain = no biff = no broken_sasl_auth_clients = yes command_directory = /usr/sbin config_directory = /etc/postfix content_filter = amavisfeed:[127.0.0.1]:10024 daemon_directory = /usr/libexec/postfix debug_peer_level = 2 disable_vrfy_command = yes html_directory = no inet_interfaces = all mail_owner = postfix mail_spool_directory = /var/spool/mail mailbox_size_limit = 0 mailq_path = /usr/bin/mailq manpage_directory = /usr/share/man message_size_limit = 20480000 mydestination = $myhostname, localhost, localhost.$mydomain mydomain = my-domain.com myhostname = myers.my-domain.com mynetworks = 127.0.0.0/8, 74.125.113.27, 74.125.82.49, 74.125.79.27, 209.85.161.0/24, 209.85.214.0/24, 209.85.216.0/24, 209.85.212.0/24, 209.85.160.0/24 myorigin = $myhostname newaliases_path = /usr/bin/newaliases queue_directory = /var/spool/postfix readme_directory = /usr/share/doc/postfix-2.3.3/README_FILES receive_override_options = no_address_mappings recipient_delimiter = + relay_domains = $mydestination sample_directory = /usr/share/doc/postfix-2.3.3/samples sendmail_path = /usr/sbin/sendmail setgid_group = postdrop smtp_bind_address = my-primary-server's IP address smtpd_banner = mail.my-domain.com smtpd_helo_required = yes smtpd_sasl_auth_enable = yes smtpd_sasl_path = private/auth smtpd_sasl_type = dovecot smtpd_tls_auth_only = yes smtpd_tls_cert_file = /etc/ssl/mailserver/postfix.pem smtpd_tls_key_file = /etc/ssl/mailserver/private/postfix.pem smtpd_tls_loglevel = 3 smtpd_tls_received_header = no smtpd_tls_session_cache_timeout = 3600s smtpd_use_tls = yes tls_random_source = dev:/dev/urandom unknown_local_recipient_reject_code = 554 virtual_alias_maps = mysql:/etc/postfix/mysql-virtual-alias-maps.cf,mysql:/etc/postfix/mysql-email2email.cf virtual_gid_maps = static:5000 virtual_mailbox_base = /var/vmail virtual_mailbox_domains = mysql:/etc/postfix/mysql-virtual-mailbox-domains.cf virtual_mailbox_maps = mysql:/etc/postfix/mysql-virtual-mailbox-maps.cf virtual_minimum_uid = 5000 virtual_transport = dovecot virtual_uid_maps = static:5000 If anyone has any ideas and can help me finally solve this issue once and for all, I'd be eternally grateful.

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• How to setup linux permissions for the WWW folder?

  - by Xeoncross

  Updated Summery The /var/www directory is owned by root:root which means that no one can use it and it's entirely useless. Since we all want a web server that actually works (and no-one should be logging in as "root"), then we need to fix this. Only two entities need access. PHP/Perl/Ruby/Python all need access to the folders and files since they create many of them (i.e. /uploads/). These scripting languages should be running under nginx or apache (or even some other thing like FastCGI for PHP). The developers How do they get access? I know that someone, somewhere has done this before. With however-many billions of websites out there you would think that there would be more information on this topic. I know that 777 is full read/write/execute permission for owner/group/other. So this doesn't seem to be needed as it leaves random users full permissions. What permissions are need to be used on /var/www so that... Source control like git or svn Users in a group like "websites" (or even added to "www-data") Servers like apache or lighthttpd And PHP/Perl/Ruby can all read, create, and run files (and directories) there? If I'm correct, Ruby and PHP scripts are not "executed" directly - but passed to an interpreter. So there is no need for execute permission on files in /var/www...? Therefore, it seems like the correct permission would be chmod -R 1660 which would make all files shareable by these four entities all files non-executable by mistake block everyone else from the directory entirely set the permission mode to "sticky" for all future files Is this correct? Update: I just realized that files and directories might need different permissions - I was talking about files above so i'm not sure what the directory permissions would need to be. Update 2: The folder structure of /var/www changes drastically as one of the four entities above are always adding (and sometimes removing) folders and sub folders many levels deep. They also create and remove files that the other 3 entities might need read/write access to. Therefore, the permissions need to do the four things above for both files and directories. Since non of them should need execute permission (see question about ruby/php above) I would assume that rw-rw-r-- permission would be all that is needed and completely safe since these four entities are run by trusted personal (see #2) and all other users on the system only have read access. Update 3: This is for personal development machines and private company servers. No random "web customers" like a shared host. Update 4: This article by slicehost seems to be the best at explaining what is needed to setup permissions for your www folder. However, I'm not sure what user or group apache/nginx with PHP OR svn/git run as and how to change them. Update 5: I have (I think) finally found a way to get this all to work (answer below). However, I don't know if this is the correct and SECURE way to do this. Therefore I have started a bounty. The person that has the best method of securing and managing the www directory wins.

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• Oracle performance problem

  - by jreid42

  We are using an Oracle 11G machine that is very powerful; has redundant storage etc. It's a beast from what I have been told. We just got this DB for a tool that when I first came on as a coop had like 20 people using, now its upwards of 150 people. I am the only one working on it :( We currently have a system in place that distributes PERL scripts across our entire data center essentially giving us a sort of "grid" computing power. The Perl scripts run a sort of simulation and report back the results to the database. They do selects / inserts. The load is not very high for each script but it could be happening across 20-50 systems at the same time. We then have multiple data centers and users all hitting the same database with this same approach. Our main problem with this is that our database is getting overloaded with connections and having to drop some. We sometimes have upwards of 500 connections. These are old perl scripts and they do not handle this well. Essentially they fail and the results are lost. I would rather avoid having to rewrite a lot of these as they are poorly written, and are a headache to even look at. The database itself is not overloaded, just the connection overhead is too high. We open a connection, make a quick query and then drop the connection. Very short connections but many of them. The database team has basically said we need to lower the number of connections or they are going to ignore us. Because this is distributed across our farm we cant implement persistent connections. I do this with our webserver; but its on a fixed system. The other ones are perl scripts that get opened and closed by the distribution tool and thus arent always running. What would be my best approach to resolving this issue? The scripts themselves can wait for a connection to be open. They do not need to act immediately. Some sort of queing system? I've been suggested to set up a few instances of a tool called "SQL Relay". Maybe one in each data center. How reliable is this tool? How good is this approach? Would it work for what we need? We could have one for each data center and relay requests through it to our main database, keeping a pipeline of open persistent connections? Does this make sense? Is there any other suggestions you can make? Any ideas? Any help would be greatly appreciated. Sadly I am just a coop student working for a very big company and somehow all of this has landed all on my shoulders (there is literally nobody to ask for help; its a hardware company, everybody is hardware engineers, and the database team is useless and in India) and I am quite lost as what the best approach would be? I am extremely overworked and this problem is interfering with on going progress and basically needs to be resolved as quickly as possible; preferably without rewriting the whole system, purchasing hardware (not gonna happen), or shooting myself in the foot. HELP LOL!

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• Kernel Mode Rootkit

  - by Pajarito

  On the other 3 computers in my family, I believe that we have a kernel-mode rootkit for windows. It appears that the same rootkit is on all of them. We think. We changed all the important passwords from my computer, running linux right now. On all of the infected computers is Symantic Endpoint Protection, because it's free from the university where my mom and dad work. In my opinion symantec is a piece of crap, seeing as it didn't even manager to delete the tracking cookies it found when I tried it on my own computer. The Computers and their set-ups: Computer A: Vista Business; symantec antivirus. runs it as admin, no password. IE8. no other security software other than what comes with windows. IE8 security settings the default Computer B: XP Home Premium; symantec antivirus. runs as normal user, no password, admin account with weak password, spybot, uses IE8 with default settings, sometimes Firefox Computer C: XP Home Premium; symantec antivirus. runs as normal user, no password, admin account with weak password, uses IE8 with default settings, no other security programs except what came with windows This is what's happening. Cut and pasted from my dad's forum post. -- When I scanned my laptop (Dell XPS M1330 with Windows Vista Small Business), Symantec Endpoint Protection hangs for a while, perhaps 10 seconds or so, on some of the following files 9129837.exe, hide_evr2.sys, VirusRemoval.vbs, NewVirusRemoval.vbs, dll.dll, alsmt.ext, and _epnt.sys. It does this if a run a scan that I set up to run on a new thumbnail drive and it does this even if the thumbnail is not plugged in. It doesn't seem to do this if I scan only the C: drive. I've check for problems with symantec endpoint protection and also with Microsoft Security Essentials and Malwarebytes Anti-Malware. They found nothing and I can't find anything by searching for hidden files. Next I tried microsoft's rootkitrevealer. It (rootkitrevealer) finds 279660 (or so) discrepancies and the interface is so glitchy after that I can't really figure out what is going on. The screen is squirrely. The rootkitrevealer pulls up many files in the folder \programdata\applicationdata and there are numberous appended \applicationdata on the end of that as well. -- As you can see, what we did was install MSE and MBAM and scan with both of them. Nothing but a tracking cookie. Then I took over and ran rootkitrevealer.exe from MicroSoft from a flash drive. It found a bunch of discrepancies, but only about 20 or so where security related, the rest being files that you just couldn't see from Windows Explorer. I couldn't see whether of not the files list above, the ones that the scan was hanging on, where in the list. The other thing is, I have no idea what to do about the things the scan comes up with. Then we checked the other computers and they do the same thing when you scan with Symantec. The people at the university seen to think that dad might not have a virus, but 2 of the computers slowed down noticably AND IE8 started acting all funny. None of my family is very computer oriented, and 2 of the possible causes for the rootkit are: -My dad bought a new flash drive, which shipped with a data security executable on it -My dad has to download lots of articles for his work Those are the only things that stand out, but it could have been anything. We are currently backing up our data, and I'll post again after trying IceSword 1.22. I just looked at my dad's forum topic, and someone recommended GMER. I'll try that too.

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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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• Sharepoint AD imported users are becomming sporadically corrupted, causing us to have to create a new account

  - by TrevJen

  Sharepoint 2007 MOSS with AD imported users. All servers are 2008. ***UPDATE More details in testing. This Sharepoint is in an AD Child domain (clients.mycompany.local), which is sub to the root of the AD tree (mycompany.local). The user is in the parent tree (as are half of the other functional users. I have elevated the user rights to Domain. In looking at the logs, it seems that the Sharepoint server is trying to authenticate them by querying the DC for the clients domain (which is the way it normally works and still works for all existing identically configured users). I think if I could force it to authenticate up to the top domain DC then it would be ok?? I have around 50 users, over the past 2 months, I have had a handful of the users suddenly unable to login to Sharepoint. When they login, they either get a blank screen or they are repropmted. These users are using accounts that have been used for many months, sometimes the problem originates with a password change. In all cases, the users account works on every other Active Directory authenticated resource (domain, exchange, LDAP). In the most recent case, last night I was forced deleted a user ("John smith") because of corruption. The orifinal account name was jsmith. I deleted him from active directory, then deleted him from the profile list in Sharepoint Shared Services. I could not find a way to delete him from the Sharepoint user list, but I reran the import after recreating his account (renamed it too just to be sure to "smithj"). At first, this did not wor, the user could still access all other resources but Sharepoint. then, some 30 minutes later it inexplicably started working. This morning, the user changed passwords, which immediatly broke the login on Sharepoint again. Logs by request from matt b Office SharePoint Server Date: 4/13/2010 2:00:00 PM Event ID: 7888 Task Category: Office Server General Level: Error Keywords: Classic User: N/A Computer: nb-portal-01.clients.netboundary.local Description: A runtime exception was detected. Details follow. Message: Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED)) – TrevJen 19 hours ago Techinal Details: System.UnauthorizedAccessException: Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED)) at Microsoft.SharePoint.SPGlobal.HandleUnauthorizedAccessException(UnauthorizedAccessException ex) at Microsoft.SharePoint.Library.SPRequest.UpdateField(String bstrUrl, String bstrListName, String bstrXML) at Microsoft.SharePoint.SPField.UpdateCore(Boolean bToggleSealed) – TrevJen 19 hours ago at Microsoft.SharePoint.SPField.Update() at Microsoft.Office.Server.UserProfiles.SiteSynchronizer.UserSynchronizer.PushSchemaToList(Boolean& bAddedColumn) at Microsoft.Office.Server.UserProfiles.SiteSynchronizer.UserSynchronizer.SynchFull() at Microsoft.Office.Server.UserProfiles.SiteSynchronizer.Synch() at Microsoft.Office.Server.Diagnostics.FirstChanceHandler.ExceptionFilter(Boolean fRethrowException, TryBlock tryBlock, FilterBlock filter, CatchBlock catchBlock, FinallyBlock finallyBlock) – TrevJen 19 hours ago Log Name: Application Source: Office SharePoint Server Date: 4/13/2010 2:00:00 PM Event ID: 5553 Task Category: User Profiles Level: Error Keywords: Classic User: N/A Computer: nb-portal-01.clients.netboundary.local Description: failure trying to synch site 6fea15e2-0899-4c19-9016-44d77834c018 for ContentDB b2002b0b-3d4c-411a-8c4f-3d047ca9322c WebApp 3aff7051-455d-4a70-a377-5b1c36df618e. Exception message was Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED)). – TrevJen 18 hours ago

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• Determining cause of high NFS/IO utilization without iotop

  - by Matt

  I have a server that is doing an NFSv4 export for user's home directories. There are roughly 25 users (mostly developers/analysts) and about 40 servers mounting the home directory export. Performance is miserable, with users often seeing multi-second lags for simple commands (like ls, or writing a small text file). Sometimes the home directory mount completely hangs for minutes, with users getting "permission denied" errors. The hardware is a Dell R510 with dual E5620 CPUs and 8 GB RAM. There are eight 15k 2.5” 600 GB drives (Seagate ST3600057SS) configured in hardware RAID-6 with a single hot spare. RAID controller is a Dell PERC H700 w/512MB cache (Linux sees this as a LSI MegaSAS 9260). OS is CentOS 5.6, home directory partition is ext3, with options “rw,data=journal,usrquota”. I have the HW RAID configured to present two virtual disks to the OS: /dev/sda for the OS (boot, root and swap partitions), and /dev/sdb for the home directories. What I find curious, and suspicious, is that the sda device often has very high utilization, even though it only contains the OS. I would expect this virtual drive to be idle almost all the time. The system is not swapping, according to "free" and "vmstat". Why would there be major load on this device? Here is a 30-second snapshot from iostat: Time: 09:37:28 AM Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await svctm %util sda 0.00 44.09 0.03 107.76 0.13 607.40 11.27 0.89 8.27 7.27 78.35 sda1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 sda2 0.00 44.09 0.03 107.76 0.13 607.40 11.27 0.89 8.27 7.27 78.35 sdb 0.00 2616.53 0.67 157.88 2.80 11098.83 140.04 8.57 54.08 4.21 66.68 sdb1 0.00 2616.53 0.67 157.88 2.80 11098.83 140.04 8.57 54.08 4.21 66.68 dm-0 0.00 0.00 0.03 151.82 0.13 607.26 8.00 1.25 8.23 5.16 78.35 dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 dm-2 0.00 0.00 0.67 2774.84 2.80 11099.37 8.00 474.30 170.89 0.24 66.84 dm-3 0.00 0.00 0.67 2774.84 2.80 11099.37 8.00 474.30 170.89 0.24 66.84 Looks like iotop is the ideal tool to use to sniff out these kinds of issues. But I'm on CentOS 5.6, which doesn't have a new enough kernel to support that program. I looked at Determining which process is causing heavy disk I/O?, and besides iotop, one of the suggestions said to do a "echo 1 /proc/sys/vm/block_dump". I did that (after directing kernel messages to tempfs). In about 13 minutes I had about 700k reads or writes, roughly half from kjournald and the other half from nfsd: # egrep " kernel: .*(READ|WRITE)" messages | wc -l 768439 # egrep " kernel: kjournald.*(READ|WRITE)" messages | wc -l 403615 # egrep " kernel: nfsd.*(READ|WRITE)" messages | wc -l 314028 For what it's worth, for the last hour, utilization has constantly been over 90% for the home directory drive. My 30-second iostat keeps showing output like this: Time: 09:36:30 PM Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await svctm %util sda 0.00 6.46 0.20 11.33 0.80 71.71 12.58 0.24 20.53 14.37 16.56 sda1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 sda2 0.00 6.46 0.20 11.33 0.80 71.71 12.58 0.24 20.53 14.37 16.56 sdb 137.29 7.00 549.92 3.80 22817.19 43.19 82.57 3.02 5.45 1.74 96.32 sdb1 137.29 7.00 549.92 3.80 22817.19 43.19 82.57 3.02 5.45 1.74 96.32 dm-0 0.00 0.00 0.20 17.76 0.80 71.04 8.00 0.38 21.21 9.22 16.57 dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 dm-2 0.00 0.00 687.47 10.80 22817.19 43.19 65.48 4.62 6.61 1.43 99.81 dm-3 0.00 0.00 687.47 10.80 22817.19 43.19 65.48 4.62 6.61 1.43 99.82

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