Search Results

Search found 25049 results on 1002 pages for 'dev null'.

Page 2/1002 | < Previous Page | 1 2 3 4 5 6 7 8 9 10 11 12  | Next Page >

• "Null" is null or not an object error in IE javascript

  - by rossmcm

  The following code executes fine in Firefox and Chrome, but gives an error: 'null' is null or not an object when executed in Internet Explorer. if (xmlhttp.responseXML != null) { var xmlDoc = xmlhttp.responseXML.documentElement ; var ResultNodes = xmlDoc.getElementsByTagName ("Result") ; <---- error here if (ResultNodes != null) { (I would have thought the line after the one indicated would be more likely to return the error but the debugger says the run-time error is at the line indicated) Any ideas why?

  Read the article

• Mount TMPFS instead of ro /dev

  - by schiggn

  I am working on a ARM-Based embedded system with a custom Debian Linux based on kernel 2.6.31. In the final system, the Root file system is stored as squashfs on flash. Now, the folder /dev is created by udev, but since there is no hot plugging functionality needed and booting time is critical, I wanted to delete udev and "hard code" the /dev folder (read here, page 5). because i still need to change parameters of the devices (with ioctl /sysfs) this does not work for me in this case. so i thought of mounting a tmpfs on /dev and change the parameters there. is this possible? and how to do best? my approach would be: delete /dev from RFS create tar containing basic devices mount tmpfs /dev untar tar-file into /dev change parameters Could this work? Do you see any problems? I found out, that you can mount on top of already mounted mount point, is it somehow possible just to take data with while mounting the new file system? if so that would be very convenient! Thanks Update: I just tried that out, but I'm stuck at a certain point. I packed all my devices into devices.tar, packed it into /usr of my squashfs and added the following lines to mountkernfs.sh, which is executed right after INIT. #mount /dev on tmpfs echo -n "Mounting /dev on tmpfs..." mount -o size=5M,mode=0755 -t tmpfs tmpfs /dev mknod -m 600 /dev/console c 5 1 mknod -m 600 /dev/null c 1 3 echo "done." echo -n "Populating /dev..." tar -xf /usr/devices.tar -C /dev echo "done." This works fine on the version over NFS, if I place printf's in the code, I can see it executing, if I comment out the extracting part, its complaining about missing devices. Booting OK mmc0: new high speed SDHC card at address 0007 mmcblk0: mmc0:0007 SD04G 3.67 GiB mmcblk0: p1 IP-Config: Unable to set interface netmask (-22). Looking up port of RPC 100003/2 on 192.168.1.234 Looking up port of RPC 100005/1 on 192.168.1.234 VFS: Mounted root (nfs filesystem) on device 0:14. Freeing init memory: 136K INIT: version 2.86 booting Mounting /dev on tmpfs...done. Populating /dev...done. Initializing /var...done. Setting the system clock. System Clock set to: Thu Sep 13 11:26:23 UTC 2012. INIT: Entering runlevel: 2 UBI: attaching mtd8 to ubi0 Commenting out the extraction of the tar mmc0: new high speed SDHC card at address 0007 mmcblk0: mmc0:0007 SD04G 3.67 GiB mmcblk0: p1 IP-Config: Unable to set interface netmask (-22). Looking up port of RPC 100003/2 on 192.168.1.234 Looking up port of RPC 100005/1 on 192.168.1.234 VFS: Mounted root (nfs filesystem) on device 0:14. Freeing init memory: 136K INIT: version 2.86 booting Mounting /dev on tmpfs...done. Populating /dev...done. Initializing /var...done. Setting the system clock. Cannot access the Hardware Clock via any known method. Use the --debug option to see the details of our search for an access method. Unable to set System Clock to: Thu Sep 13 12:24:00 UTC 2012 ... (warning). INIT: Entering runlevel: 2 libubi: error!: cannot open "/dev/ubi_ctrl" So far so good. But if I pack the whole story into a squashfs and boot from there, it is acting strange. It's telling me while booting that it is unable to open an initial console and its throwing errors on mounting the UBIFS devices, but finally provides a login anyway. Over that my echo's are not executed. If I then log in, /dev is mounted as TMPFS as desired and all the devices reside inside. When I redo the "mount" command to mount the UBIFS partitions it is executed whitout problem and useable. From squashfs VFS: Mounted root (squashfs filesystem) readonly on device 31:15. Freeing init memory: 136K Warning: unable to open an initial console. mmc0: new high speed SDHC card at address 0007 mmcblk0: mmc0:0007 SD04G 3.67 GiB mmcblk0: p1 UBIFS error (pid 484): ubifs_get_sb: cannot open "ubi1_0", error -19 Additionally, a part of the rest of the bootscripts is still exexuted, but not all of them. Does anyone has a clue why? Other question, is 5MB enough/too much for /dev?

  Read the article

• Null object that is not null

  - by Guillaume

  Hello, I use 2 threads to act like a produce/consumer using double queue (http://www.codeproject.com/KB/threads/DoubleQueue.aspx). Sometimes in my 2nd thread, I get an object that is NULL but it should not be as I filled it in the first thread. I tried this: if(myObject.Data == null) { Console.WriteLine("Null Object") // <-- Breakpoint here } When I my break point hits, I can watch myObject.Data and indeed it's NULL, but when I hit F10 and then go to the next line (which is } ) myObject.Data is not NULL. I also added a lock on myObject before if .... to be sure that no one whould use this object. How is that possible and what can I do ?

  Read the article

• Returning null vs Throwing exceptions

  - by Svish

  Is in a bit of disagreement with a more experienced developer on this issue, and was wondering what you guys here think about this. Environment is Java, EJB 3, services, etc. The code I wrote calls a service to get things and to create things. Problem was that I got null pointer exceptions in places that didn't make sense. For example when I asked the service to create an object, I got null back. And when I tried to look up an object with an id I knew existed, I still got null back. Was like it was ignoring me. Spent some time trying to figure out what was wrong in my code (since I'm less experienced I usually assume I have messed up). Turns out the reason was security. If the user principal using my service didn't have the right permissions to use the service I called from my service, then that service simply returned null. The services that are here already are usually not documented either, so this is just something you have to know... somehow... So here is the thing: I mean that this is rather confusing as a developer interacting with this service. To me it would make much more sense if that service thew an exception which would tell me that hey, you don't have the proper permissions to get info about this thing or to create this new thing. I would then immediately know why my service wasn't working as expected. However, he argued that asking is not wrong. Exceptions should only be thrown when there is an error and asking for a thing is not an error. Even if you don't have permission to "see" that the thing you asked for. The things are often looked up in a GUI by users and for those users not having the right permissions, these things simply "do not exist". So, in short: Asking is not wrong, hence no exception. Get methods return null because to those users those things "doesn't exist". Create methods return null because nothing was created, since the user wasn't allowed to create anything. So, what do you guys think? Is this normal and/or good practice? I prefer exceptions as I prefer throwing and catching exceptions because I find it much easier to know what's going on. So I would for example also prefer to throw a NotFoundException if you asked for an id which didn't exist, rather than returning null. Anyways, just curious to what others think about this as I'm not the most experienced developer yet.

  Read the article

• #define NULL NULL

  - by sheepsimulator

  #ifndef NULL #define NULL NULL #endif This code compiles in gcc with no warnings/errors. Can someone explain what the preprocessor is doing here?

  Read the article

• which is more effective [ if(NULL==variables) or if(variables==NULL) ]

  - by Apache

  hi expert, want to ask, in java if(NULL==variables) or if(variables==NULL) which will be more effective and what are the difference, thanks

  Read the article

• MySQL Database Query Problem

  - by moustafa

  I need your help!!!. I need to query a table in my database that has record of goods sold. I want the query to detect a particular product and also calculate the quantity sold. The product are 300 now, but it would increase in the future. Below is a sample of my DB Table #---------------------------- # Table structure for litorder #---------------------------- CREATE TABLE `litorder` ( `id` int(10) NOT NULL auto_increment, `name` varchar(50) NOT NULL default '', `address` varchar(50) NOT NULL default '', `xdate` date NOT NULL default '0000-00-00', `ref` varchar(20) NOT NULL default '', `code1` varchar(50) NOT NULL default '', `code2` varchar(50) NOT NULL default '', `code3` varchar(50) NOT NULL default '', `code4` varchar(50) NOT NULL default '', `code5` varchar(50) NOT NULL default '', `code6` varchar(50) NOT NULL default '', `code7` varchar(50) NOT NULL default '', `code8` varchar(50) NOT NULL default '', `code9` varchar(50) NOT NULL default '', `code10` varchar(50) NOT NULL default '', `code11` varchar(50) character set latin1 collate latin1_bin NOT NULL default '', `code12` varchar(50) NOT NULL default '', `code13` varchar(50) NOT NULL default '', `code14` varchar(50) NOT NULL default '', `code15` varchar(50) NOT NULL default '', `product1` varchar(100) NOT NULL default '0', `product2` varchar(100) NOT NULL default '0', `product3` varchar(100) NOT NULL default '0', `product4` varchar(100) NOT NULL default '0', `product5` varchar(100) NOT NULL default '0', `product6` varchar(100) NOT NULL default '0', `product7` varchar(100) NOT NULL default '0', `product8` varchar(100) NOT NULL default '0', `product9` varchar(100) NOT NULL default '0', `product10` varchar(100) NOT NULL default '0', `product11` varchar(100) NOT NULL default '0', `product12` varchar(100) NOT NULL default '0', `product13` varchar(100) NOT NULL default '0', `product14` varchar(100) NOT NULL default '0', `product15` varchar(100) NOT NULL default '0', `price1` int(10) NOT NULL default '0', `price2` int(10) NOT NULL default '0', `price3` int(10) NOT NULL default '0', `price4` int(10) NOT NULL default '0', `price5` int(10) NOT NULL default '0', `price6` int(10) NOT NULL default '0', `price7` int(10) NOT NULL default '0', `price8` int(10) NOT NULL default '0', `price9` int(10) NOT NULL default '0', `price10` int(10) NOT NULL default '0', `price11` int(10) NOT NULL default '0', `price12` int(10) NOT NULL default '0', `price13` int(10) NOT NULL default '0', `price14` int(10) NOT NULL default '0', `price15` int(10) NOT NULL default '0', `quantity1` int(10) NOT NULL default '0', `quantity2` int(10) NOT NULL default '0', `quantity3` int(10) NOT NULL default '0', `quantity4` int(10) NOT NULL default '0', `quantity5` int(10) NOT NULL default '0', `quantity6` int(10) NOT NULL default '0', `quantity7` int(10) NOT NULL default '0', `quantity8` int(10) NOT NULL default '0', `quantity9` int(10) NOT NULL default '0', `quantity10` int(10) NOT NULL default '0', `quantity11` int(10) NOT NULL default '0', `quantity12` int(10) NOT NULL default '0', `quantity13` int(10) NOT NULL default '0', `quantity14` int(10) NOT NULL default '0', `quantity15` int(10) NOT NULL default '0', `amount1` int(10) NOT NULL default '0', `amount2` int(10) NOT NULL default '0', `amount3` int(10) NOT NULL default '0', `amount4` int(10) NOT NULL default '0', `amount5` int(10) NOT NULL default '0', `amount6` int(10) NOT NULL default '0', `amount7` int(10) NOT NULL default '0', `amount8` int(10) NOT NULL default '0', `amount9` int(10) NOT NULL default '0', `amount10` int(10) NOT NULL default '0', `amount11` int(10) NOT NULL default '0', `amount12` int(10) NOT NULL default '0', `amount13` int(10) NOT NULL default '0', `amount14` int(10) NOT NULL default '0', `amount15` int(10) NOT NULL default '0', `totalNaira` double(20,0) NOT NULL default '0', `totalDollar` int(20) NOT NULL default '0', PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 COMMENT='InnoDB free: 4096 kB; InnoDB free: 4096 kB; InnoDB free: 409'; #---------------------------- # Records for table litorder #---------------------------- insert into litorder values (27, 'Sanyaolu Fisayo', '14 Adegboyega Street Palmgrove Lagos', '2010-05-31', '', 'DL 001', 'DL 002', 'DL 003', '', '', '', '', '', '', '', '', '', '', '', '', 'AILMENT & PREVENTION DVD- ENGLISH', 'AILMENT & PREVENTION DVD- HAUSA', 'BEAUTY CD', '', '', '', '', '', '', '', '', '', '', '', '', 800, 800, 3000, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 16, 16, 20, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 12800, 12800, 60000, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, '85600', 563), (28, 'Irenonse Esther', 'Lagos,Nigeria', '2010-06-01', '', 'DL 005', 'DL 008', 'FC 004', '', '', '', '', '', '', '', '', '', '', '', '', 'GET HEALTHY DVD', 'YOUR FUTURE DVD', 'FOREVER FACE CAP (YELLOW)', '', '', '', '', '', '', '', '', '', '', '', '', 1000, 900, 2000, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 2, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2000, 1800, 6000, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, '9800', 64), (29, 'Kalu Lekway', 'Lagos, Nigeria', '2010-06-01', '', 'DL 001', 'DL 003', '', '', '', '', '', '', '', '', '', '', '', '', '', 'AILMENT & PREVENTION DVD- ENGLISH', 'BEAUTY CD', '', '', '', '', '', '', '', '', '', '', '', '', '', 800, 3000, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2400, 18000, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, '20400', 133), (30, 'Dele', 'Ilupeju', '2010-06-02', '', 'DL 001', 'DL 003', '', '', '', '', '', '', '', '', '', '', '', '', '', 'AILMENT & PREVENTION DVD- ENGLISH', 'BEAUTY CD', '', '', '', '', '', '', '', '', '', '', '', '', '', 800, 3000, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 10, 10, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 8000, 30000, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, '38000', 250);

  Read the article

• null coalescing operator for javascript?

  - by Daniel Schaffer

  I assumed this question has already been asked here, but I couldn't find any, so here it goes: Is there a null coalescing operator in Javascript? For example, in C#, I can do this: String someString = null; var whatIWant = someString ?? "Cookies!"; The best approximation I can figure out for Javascript is using the conditional operator: var someString = null; var whatIWant = someString ? someString : 'Cookies!'; Which is sorta icky IMHO. Can I do better?

  Read the article

• Dev Docs and another Responsive Bookmarklet

  - by ihaynes

  Originally posted on: http://geekswithblogs.net/ihaynes/archive/2013/07/30/dev-docs-and-another-responsive-bookmarklet.aspxI came across two sources of developer documentation today, courtesy of the LinkedIn CSS3/HTML5 group. The first, DocHub http://dochub.io/#css/  and the second, DevDocs http://devdocs.io/Another Responsive Bookmarklet by Victor Coulon was also mentioned. http://responsive.victorcoulon.fr/

  Read the article

• [Not in Vermont] IT Jobs: Sharepoint/ASP.NET Dev + Winforms C# Dev in Western Mass

  Two .NET jobs in Western Mass from a recruiter, contact info below Requirement #1: Our client is looking for the best engineers in the world, and then we give them the opportunity to excel. Our light, scrum-based process keeps you focused on delivering functionality that our customers need. We try to do things right (unit tests, continuous builds, bug tracking, etc) and were looking for others who work this way too. Primary Responsibilities Develop SharePoint applications in ASP.NET with a heavy...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

  Read the article

• How to upgrade boost lib using apt-get?

  - by sam

  I use ubuntu 11.04. My boost version: sam@sam:~/code/ros/pcl$ apt-cache showpkg libboost-all-dev Package: libboost-all-dev Versions: 1.42.0.1ubuntu1 (/var/lib/apt/lists/tw.archive.ubuntu.com_ubuntu_dists_natty_universe_binary-amd64_Packages) (/var/lib/dpkg/status) Description Language: File: /var/lib/apt/lists/tw.archive.ubuntu.com_ubuntu_dists_natty_universe_binary-amd64_Packages MD5: 72efad05a3c79394c125b79e1d4eb3a7 Reverse Depends: libvtk5-dev,libboost-all-dev libfeel++-dev,libboost-all-dev Dependencies: 1.42.0.1ubuntu1 - libboost-dev (0 (null)) libboost-date-time-dev (0 (null)) libboost-filesystem-dev (0 (null)) libboost-graph-dev (0 (null)) libboost-iostreams-dev (0 (null)) libboost-math-dev (0 (null)) libboost-program-options-dev (0 (null)) libboost-python-dev (0 (null)) libboost-regex-dev (0 (null)) libboost-serialization-dev (0 (null)) libboost-signals-dev (0 (null)) libboost-system-dev (0 (null)) libboost-test-dev (0 (null)) libboost-thread-dev (0 (null)) libboost-wave-dev (0 (null)) Provides: 1.42.0.1ubuntu1 - Reverse Provides: sam@sam:~/code/ros/pcl$ How to upgrade boost to 1.44+ by using apt tools? Thank you~ When I run apt-add-repository,it shows: sam@sam:~/code/ros/pcl$ sudo apt-add-repository ppa:timklingt/ppa Error reading https://launchpad.net/api/1.0/~timklingt/+archive/ppa: GnuTLS recv error (-9): A TLS packet with unexpected length was received. sam@sam:~/code/ros/pcl$ How to fix it? Thank you~ I try to install libboost1.46-all-dev: sam@sam:~/code/ros/pcl$ sudo apt-get install libboost1.46-all-dev Reading package lists... Done Building dependency tree Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation: The following packages have unmet dependencies: libboost1.46-all-dev : Depends: libboost1.46-dev but it is not going to be installed Depends: libboost-date-time1.46-dev but it is not going to be installed Depends: libboost-filesystem1.46-dev but it is not going to be installed Depends: libboost-graph1.46-dev but it is not going to be installed Depends: libboost-iostreams1.46-dev but it is not going to be installed Depends: libboost-math1.46-dev but it is not going to be installed Depends: libboost-program-options1.46-dev but it is not going to be installed Depends: libboost-python1.46-dev but it is not going to be installed Depends: libboost-regex1.46-dev but it is not going to be installed Depends: libboost-serialization1.46-dev but it is not going to be installed Depends: libboost-signals1.46-dev but it is not going to be installed Depends: libboost-system1.46-dev but it is not going to be installed Depends: libboost-test1.46-dev but it is not going to be installed Depends: libboost-thread1.46-dev but it is not going to be installed Depends: libboost-wave1.46-dev but it is not going to be installed E: Broken packages sam@sam:~/code/ros/pcl$ What's these error means? And how to solve it? Thank you~

  Read the article

• ubuntu 11.10 install 4.4.3-0ubuntu2 package dependencies

  - by HuangheWoo

  before sudo apt-get install gnuplot I sudo apt-get build-dep gnuplot to resolve package dependencies. ~$ sudo apt-get build-dep gnuplot Reading package lists... Done Building dependency tree Reading state information... Done Note, selecting 'liblua5.1-0-dev' instead of 'liblua5.1-dev' The following packages will be REMOVED: libgd2-xpm ubuntu-desktop The following NEW packages will be installed: debhelper diffstat html2text intltool-debian libbsd-dev libcairo-script-interpreter2 libcairo2-dev libedit-dev libexpat1-dev libfontconfig1-dev libfreetype6-dev libgd2-noxpm libgd2-noxpm-dev libglib2.0-dev libjpeg62-dev liblua5.1-0-dev libncurses5-dev libpango1.0-dev libpixman-1-dev libpng12-dev libreadline-dev libreadline6-dev libtinfo-dev libwxbase2.8-dev libwxgtk2.8-dev libxcb-render0-dev libxcb-shm0-dev libxft-dev libxrender-dev po-debconf quilt texinfo wx2.8-headers x11proto-render-dev 0 upgraded, 34 newly installed, 2 to remove and 0 not upgraded. Need to get 9,100 kB of archives. After this operation, 37.8 MB of additional disk space will be used. It says the "ubuntu-desktop" will be removed, but "ubuntu-desktop" is important. What's should I do?

  Read the article

• wcf web service in post method, object properties are null, although the object is not null

  - by Abdalhadi Kolayb

  i have this problem in post method when i send object parameter to the method, then the object is not null, but all its properties have the default values. here is data module: [DataContract] public class Products { [DataMember(Order = 1)] public int ProdID { get; set; } [DataMember(Order = 2)] public string ProdName { get; set; } [DataMember(Order = 3)] public float PrpdPrice { get; set; } } and here is the interface: [OperationContract] [WebInvoke( Method = "POST", UriTemplate = "AddProduct", ResponseFormat = WebMessageFormat.Json, BodyStyle = WebMessageBodyStyle.WrappedRequest, RequestFormat = WebMessageFormat.Json)] string AddProduct([MessageParameter(Name = "prod")]Products prod); public string AddProduct(Products prod) { ProductsList.Add(prod); return "return string"; } here is the json request: Content-type:application/json {"prod":[{"ProdID": 111,"ProdName": "P111","PrpdPrice": 111}]} but in the server the object received: {"prod":[{"ProdID": 0,"ProdName": NULL,"PrpdPrice": 0}]}

  Read the article

• Oral Tradition Check: Two Hundred Meanings for "NULL" in SQL

  - by Thomas L Holaday

  Two decades ago, the topic of "NULL" came up in conversation with a scholarly colleague. As I remember it, he said that C.J.Date, in an essay critical of commercial implementations of SQL, had listed over two hundred meanings for NULL. To my regret, I did not persist the details; but finding that list has since been on my Bucket List. Has anyone else heard this legend? Was it perhaps not Date, but another critic of commercial implementations of SQL?

  Read the article

• Unavailable repository

  - by katrina

  I am new to Ubuntu and keep butting up against errors, such as this: Package libpng12-dev is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source However the following packages replace it: libpng12-0 E: Unable to locate package subversion E: Package 'git-core' has no installation candidate E: Package 'build-essential' has no installation candidate E: Package 'autoconf' has no installation candidate E: Package 'libtool' has no installation candidate E: Unable to locate package libxml2-dev E: Unable to locate package libgeos-dev E: Unable to locate package libpq-dev E: Unable to locate package libbz2-dev E: Package 'proj' has no installation candidate E: Unable to locate package munin-node E: Unable to locate package munin E: Unable to locate package libprotobuf-c0-dev E: Unable to locate package protobuf-c-compiler E: Unable to locate package libfreetype6-dev E: Package 'libpng12-dev' has no installation candidate E: Unable to locate package libtiff4-dev E: Unable to locate package libicu-dev E: Unable to locate package libboost-all-dev E: Unable to locate package libgdal-dev E: Unable to locate package libcairo-dev E: Unable to locate package libcairomm-1.0-dev E: Couldn't find any package by regex 'libcairomm-1.0-dev' E: Unable to locate package apache2 E: Unable to locate package apache2-dev E: Unable to locate package libagg-dev when I want to do this: sudo apt-get install subversion git-core tar unzip wget bzip2 build-essential autoconf libtool libxml2-dev libgeos-dev libpq-dev libbz2-dev proj munin-node munin libprotobuf-c0-dev protobuf-c-compiler libfreetype6-dev libpng12-dev libtiff4-dev libicu-dev libboost-all-dev libgdal-dev libcairo-dev libcairomm-1.0-dev apache2 apache2-dev libagg-dev. Any help or advice would be greatly appreciated. Or referrals to other questions...

  Read the article

• How to install Grub2 under several common scenarios

  - by Huckle

  I feel the community has long needed a clean guide on how to install Grub2 under a a few extremely common scenarios. I will accept answer as solved when it has one section per scenario and assumes nothing other than what is specified. Please add to the existing answer, wiki style, keeping to the original assumptions. Rules: 1. You cannot, at any point in the answer, invoke Ubiquity (the Ubuntu installer). 2. I strongly recommend not using any automatic boor-repair tools as they're not very educational Scenario 1: Non-booting Linux OS, No boot partition, Fix from Live CD Setup: /dev/sda1 is formatted ext* /dev/sda2 is formatted linux_swap /dev/sda1 doesn't boot because MBR is scrambled and /boot/* was erased Explain: How to boot to a Live CD / USB and restore Grub2 to the MBR and /boot of /dev/sda1 Scenario 2: Non-booting Linux OS, Boot partition, Fix from Live CD Setup: /dev/sda1 is formatted fat /dev/sda2 is formatted ext* /dev/sda3 is formatted linux_swap /dev/sda2 doesn't boot because the MBR is scrambled and /dev/sda1 was formatted Explain: How to boot to a Live CD / USB and restore Grub2 to the MBR and /dev/sda1 and then update the fstab on /dev/sda2 Scenario 3: Install on to thumb drive, Booting various OSes, From Linux OS Setup: /dev/sdb is removable media /dev/sdb1 is formatted fat /dev/sdb2 is formatted ext* /dev/sdb3 is formatted fat The MBR of /dev/sdb is otherwise not initialized You are executing from a Linux based OS installed on /dev/sda Explain: How to install Grub2 on to /dev/sdb1, mark /dev/sdb1 active, be able to chose between /dev/sdb2 and /dev/sdb3 on boot. Scenario 4: (Bonus) Install on to thumb drive, Booting ISO, From Linux OS Setup: /dev/sdb is removable media /dev/sdb1 is formatted fat /dev/sdb1 contains /iso/live.iso /dev/sdb2 is formatted ext* /dev/sdb3 is formatted fat The MBR of /dev/sdb is otherwise not initialized You are executing from a Linux based OS installed on /dev/sda Explain: How to install Grub2 on to /dev/sdb1, mark /dev/sdb1 active, be able to chose between /dev/sdb2, /dev/sdb3, and /iso/live.iso on boot.

  Read the article

• Determining distribution of NULL values

  - by AaronBertrand

  Today on the twitter hash tag #sqlhelp, @leenux_tux asked: How can I figure out the percentage of fields that don't have data ? After further clarification, it turns out he is after what proportion of columns are NULL. Some folks suggested using a data profiling task in SSIS . There may be some validity to that, but I'm still a fan of sticking to T-SQL when I can, so here is how I would approach it: Create a #temp table or @table variable to store the results. Create a cursor that loops through all...(read more)

  Read the article

• Much ado about NULL: Exploiting a kernel NULL dereference

  <b>Ksplice:</b> "We think that it&#8217;s important for developers and system administrators to be more knowledgeable about the attacks that black hats regularly use to take control of systems, and so, today, we&#8217;re going to start from where we left off and go all the way to a working exploit for a NULL pointer dereference in a toy kernel module."

  Read the article

• Is /dev in linux virtual?

  - by user973917

  Today at work a client had rm -rf /dev and ended up deleting two files in /dev/shm that forced his site to no longer work. From what I learned previously /dev is not virtual, but a fellow technician had suggested to reboot the server because /dev is virtual like /proc. Sure enough I rebooted the server and the files that the client rm -rf'd were there. So, my question is; is /dev virtual? Is it the kind of virtual like /proc? Is there more documentation on this? How can I restore the /dev files without a server reboot?

  Read the article

• What is the difference between NULL in C++ and null in Java?

  - by Stephano

  I've been trying to figure out why C++ is making me crazy typing NULL. Suddenly it hits me the other day; I've been typing null (lower case) in Java for years. Now suddenly I'm programming in C++ and that little chunk of muscle memory is making me crazy. Wikiperipatetic defines C++ NULL as part of the stddef: A macro that expands to a null pointer constant. It may be defined as ((void*)0), 0 or 0L depending on the compiler and the language. Sun's docs tells me this about Java's "null literal": The null type has one value, the null reference, represented by the literal null, which is formed from ASCII characters. A null literal is always of the null type. So this is all very nice. I know what a null pointer reference is, and thank you for the compiler notes. Now I'm a little fuzzy on the idea of a literal in Java so I read on... A literal is the source code representation of a fixed value; literals are represented directly in your code without requiring computation. There's also a special null literal that can be used as a value for any reference type. null may be assigned to any variable, except variables of primitive types. There's little you can do with a null value beyond testing for its presence. Therefore, null is often used in programs as a marker to indicate that some object is unavailable. Ok, so I think I get it now. In C++ NULL is a macro that, when compiled, defines the null pointer constant. In Java, null is a fixed value that any non-primitive can be assigned too; great for testing in a handy if statement. Java does not have pointers, so I can see why they kept null a simple value rather than anything fancy. But why did java decide to change the all caps NULL to null? Furthermore, am I missing anything here?

  Read the article

• ON DELETE RESTRICT Causing Error 150

  - by Levi Hackwith

  CREATE TABLE project ( id INTEGER NOT NULL AUTO_INCREMENT, created_at DATETIME NOT NULL, name VARCHAR(75) NOT NULL, description LONGTEXT NOT NULL, is_active TINYINT NOT NULL DEFAULT '1', PRIMARY KEY (id), INDEX(name, created_at) ) ENGINE = INNODB; CREATE TABLE role ( id INTEGER NOT NULL, name VARCHAR(50) NOT NULL, description LONGTEXT NOT NULL, PRIMARY KEY (id) ) ENGINE = INNODB; CREATE TABLE organization ( id INTEGER NOT NULL AUTO_INCREMENT, created_at DATETIME NOT NULL, name VARCHAR(100) NOT NULL, is_active TINYINT NOT NULL DEFAULT '1', PRIMARY KEY (id) ) ENGINE = INNODB; CREATE TABLE user ( id INTEGER NOT NULL AUTO_INCREMENT, created_at DATETIME NOT NULL, role_id INTEGER NOT NULL, organization_id INTEGER NOT NULL, last_login_at DATETIME NOT NULL, last_ip_address VARCHAR(25) NOT NULL, username VARCHAR(45) NOT NULL, password CHAR(32) NOT NULL, email_address VARCHAR(255) NOT NULL, first_name VARCHAR(45) NOT NULL, last_name VARCHAR(45) NOT NULL, address_1 VARCHAR(100) NOT NULL, address_2 VARCHAR(25) NULL, city VARCHAR(25) NOT NULL, state CHAR(2) NOT NULL, zip_code VARCHAR(10) NOT NULL, primary_phone_number VARCHAR(10) NOT NULL, secondary_phone_number VARCHAR(10) NOT NULL, is_primary_organization_contact TINYINT NOT NULL DEFAULT '0', is_active TINYINT NOT NULL DEFAULT '1', PRIMARY KEY (id), CONSTRAINT fk_user_role_id FOREIGN KEY (role_id) REFERENCES role (id) ON UPDATE RESTRICT ON DELETE RESTRICT, CONSTRAINT fk_user_organization_id FOREIGN KEY (organization_id) REFERENCES organization (id) ON UPDATE RESTRICT ON DELETE RESTRICT ) ENGINE = INNODB; CREATE TABLE project_user ( user_id INTEGER NOT NULL, project_id INTEGER NOT NULL, PRIMARY KEY (user_id, project_id), CONSTRAINT fk_project_user_user_id FOREIGN KEY (user_id) REFERENCES user (id) ON UPDATE RESTRICT ON DELETE CASCADE, CONSTRAINT fk_project_user_project_id FOREIGN KEY (project_id) REFERENCES project (id) ON UPDATE RESTRICT ON DELETE RESTRICT ) ENGINE = INNODB; CREATE TABLE ticket_category ( id INTEGER NOT NULL AUTO_INCREMENT, name VARCHAR(20) NOT NULL, description LONGTEXT NOT NULL, PRIMARY KEY (id) ) ENGINE = INNODB; CREATE TABLE ticket_type ( id INTEGER NOT NULL AUTO_INCREMENT, name VARCHAR(20) NOT NULL, description LONGTEXT NOT NULL, PRIMARY KEY (id) ) ENGINE = INNODB; CREATE TABLE ticket_status ( id INTEGER NOT NULL AUTO_INCREMENT, name VARCHAR(20) NOT NULL, description LONGTEXT NOT NULL, PRIMARY KEY (id) ) ENGINE = INNODB; CREATE TABLE ticket ( id INTEGER NOT NULL AUTO_INCREMENT, created_at DATETIME NOT NULL, project_id INTEGER NOT NULL, created_by INTEGER NOT NULL, submitted_by INTEGER NOT NULL, assigned_to INTEGER NULL, category_id INTEGER NOT NULL, type_id INTEGER NOT NULL, title VARCHAR(75) NOT NULL, description LONGTEXT NOT NULL, contact_type_id TINYINT NOT NULL, affects_all_clients TINYINT NOT NULL DEFAULT '0', is_billable TINYINT NOT NULL DEFAULT '1', esimated_hours DECIMAL(4, 1) NOT NULL DEFAULT '0', hours_worked DECIMAL (4, 1) NOT NULL DEFAULT '0', status_id TINYINT NOT NULL, PRIMARY KEY (id), CONSTRAINT fk_ticket_project_id FOREIGN KEY (project_id) REFERENCES project (id) ON UPDATE RESTRICT ON DELETE RESTRICT, CONSTRAINT fk_ticket_created_by FOREIGN KEY (created_by) REFERENCES user (id) ON UPDATE RESTRICT ON DELETE RESTRICT, CONSTRAINT fk_ticket_submitted_by FOREIGN KEY (submitted_by) REFERENCES user (id) ON UPDATE RESTRICT ON DELETE RESTRICT, CONSTRAINT fk_ticket_assigned_to FOREIGN KEY (assigned_to) REFERENCES user (id) ON UPDATE RESTRICT ON DELETE RESTRICT, CONSTRAINT fk_ticket_category_id FOREIGN KEY (category_id) REFERENCES ticket_category (id) ON UPDATE RESTRICT ON DELETE RESTRICT, CONSTRAINT fk_ticket_type_id FOREIGN KEY (type_id) REFERENCES ticket_type (id) ON UPDATE RESTRICT ON DELETE RESTRICT, CONSTRAINT fk_ticket_status_id FOREIGN KEY (status_id) REFERENCES ticket_status (id) ON UPDATE RESTRICT ON DELETE RESTRICT ) ENGINE = INNODB; CREATE TABLE ticket_time_entry ( id INTEGER NOT NULL AUTO_INCREMENT, user_id INTEGER NOT NULL, ticket_id INTEGER NOT NULL, started_at DATETIME NOT NULL, ended_at DATETIME NOT NULL, PRIMARY KEY (id), CONSTRAINT fk_ticket_time_entry_user_id FOREIGN KEY (user_id) REFERENCES user (id) ON UPDATE RESTRICT ON DELETE RESTRICT, CONSTRAINT fk_ticket_time_entry_ticket_id FOREIGN KEY (ticket_id) REFERENCES ticket (id) ON UPDATE RESTRICT ON DELETE RESTRICT ) ENGINE = INNODB; The ticket table's create statement causes an error 150. I have no clue why. When I remove the ON DELETE RESTRICT statements from the table declaration, it works. Why is that?

  Read the article

• null values vs "empty" singleton for optional fields

  - by Uko

  First of all I'm developing a parser for an XML-based format for 3D graphics called XGL. But this question can be applied to any situation when you have fields in your class that are optional i.e. the value of this field can be missing. As I was taking a Scala course on coursera there was an interesting pattern when you create an abstract class with all the methods you need and then create a normal fully functional subclass and an "empty" singleton subclass that always returns false for isEmpty method and throws exceptions for the other ones. So my question is: is it better to just assign null if the optional field's value is missing or make a hierarchy described above and assign it an empty singleton implementation?

  Read the article

• Avoiding null in a controller

  - by Kevin Burke

  I'm trying to work through how to write this code. def get(params): """ Fetch a user's details, or 404 """ user = User.fetch_by_id(params['id']) if not user: abort(404) # Render some template for the user... What's the best way to handle the case where the lookup fails? One principle says you should avoid returning null values from functions. These lead to mistakes and AttributeErrors etc. later on in the file. Another idea is to have fetch_by_id raise a ValueError or similar if no user exists with that id. However there's a general principle that you shouldn't use exceptions for control flow, either, which doesn't help much. What could be done better in this case?

  Read the article

• GNU/Linux: SAS-disk detected as /dev/sg7 - not as /dev/sdb

  - by Ole Tange

  I have just installed a SAS disk into a Debian server. It was detected correctly and everything was fine. Then I moved the SAS disk to a different Debian server, the same hardware model and running same version of Debian, but here the SAS disk is detected as /dev/sg7 and not /dev/sdb. smartctl -a /dev/sg7 works fine, but fdisk and cat hang. I tried putting the SAS disk in another slot: Same problem. How can I force the SAS disk to be detected as /dev/sdb? # uname -a Linux maxwell 3.2.0-4-amd64 #1 SMP Debian 3.2.41-2+deb7u2 x86_64 GNU/Linux

  Read the article

• Comparable and Comparator contract with regards to null

  - by polygenelubricants

  Comparable contract specifies that e.compareTo(null) must throw NullPointerException. From the API: Note that null is not an instance of any class, and e.compareTo(null) should throw a NullPointerException even though e.equals(null) returns false. On the other hand, Comparator API mentions nothing about what needs to happen when comparing null. Consider the following attempt of a generic method that takes a Comparable, and return a Comparator for it that puts null as the minimum element. static <T extends Comparable<? super T>> Comparator<T> nullComparableComparator() { return new Comparator<T>() { @Override public int compare(T el1, T el2) { return el1 == null ? -1 : el2 == null ? +1 : el1.compareTo(el2); } }; } This allows us to do the following: List<Integer> numbers = new ArrayList<Integer>( Arrays.asList(3, 2, 1, null, null, 0) ); Comparator<Integer> numbersComp = nullComparableComparator(); Collections.sort(numbers, numbersComp); System.out.println(numbers); // "[null, null, 0, 1, 2, 3]" List<String> names = new ArrayList<String>( Arrays.asList("Bob", null, "Alice", "Carol") ); Comparator<String> namesComp = nullComparableComparator(); Collections.sort(names, namesComp); System.out.println(names); // "[null, Alice, Bob, Carol]" So the questions are: Is this an acceptable use of a Comparator, or is it violating an unwritten rule regarding comparing null and throwing NullPointerException? Is it ever a good idea to even have to sort a List containing null elements, or is that a sure sign of a design error?

  Read the article

< Previous Page | 1 2 3 4 5 6 7 8 9 10 11 12  | Next Page >