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• Cannot connect to FTP server from external host

  - by h3.

  I have a FTP server (vsftpd) setuped on a Linux box (Ubuntu server). When I try to connect with a computer on the same network everything works fine as expected. But as soon the IP is external it won't connect.. I first assumed the port was blocked, but then: localserver:$ sudo tail -f /var/log/vsftpd.log Wed Jan 13 14:21:17 2010 [pid 2407] CONNECT: Client "xxx.xxx.107.4" remotemachine:$ netcat svn-motion.no-ip.biz 21 220 FTP Server And it hangs there. Do any ports other than 21 need to be open?

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• How often do you review fundamentals?

  - by mlnyc

  So I've been out of school for a year and a half now. In school, of course we covered all the fundamentals: OS, databases, programming languages (i.e. syntax, binding rules, exception handling, recursion, etc), and fundamental algorithms. the rest were more in-depth topics on things like NLP, data mining, etc. Now, a year ago if you would have told me to write a quicksort, or reverse a singly-linked list, analyze the time complexity of this 'naive' algorithm vs it's dynamic programming counterpart, etc I would have been able to give you a decent and hopefully satisfying answer. But if you would have asked me more real world questions I might have been stumped (things like how would handle logging for an application, or security difference between GET and POST, differences between SQL Server and Oracle SQL, anything I list on my resume as currently working with [jQuery questions, ColdFusion questions, ...] etc) Now, I feel things are the opposite. I haven't wrote my own sort since graduating, and I don't really have to worry much about theoretical things that do not naturally fall into problems I am trying to solve. For example, I might give you some great SQL solutions using an analytical function that I would have otherwise been stumped on or write a cool web application using angular or something but ask me to write an algo for insertAfter(Element* elem) and I might not be able to do it in a reasonable time frame. I guess my question here to the experienced programmers is how do you balance the need to both learn and experiment with new technologies (fun!), working on personal projects (also fun!) working and solving real world problems in a timeboxed environment (so I might reach out to a library that does what I want rather than re-invent the wheel so that I can focus on the problem I am trying to solve) (work, basically), and refreshing on old theoretical material which is still valid for interviews and such (can be a drag)? Do you review older material (such as famous algorithms, dynamic programming, Big-O analysis, locking implementations) regularly or just when you need it? How much time do you dedicate to both in your 'deliberate practice' and do you have a certain to-do list of topics that you want to work on?

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• My feenix nascita mouse isn't moving my cursor. Ubuntu version appears to not matter. How do I debug this, and get the mouse working?

  - by NullVoxPopuli

  I had 13.04, upgraded to 13.10, and did a fresh install of 13.10, no luck. Any ideas? Just tail -f'd my syslog and plugged in the mouse. here is what I got: Oct 26 16:15:50 Orithyia kernel: [83369.618365] usb 1-1.5.2: new full-speed USB device number 6 using ehci-pci Oct 26 16:15:50 Orithyia kernel: [83369.718913] usb 1-1.5.2: New USB device found, idVendor=04d9, idProduct=a081 Oct 26 16:15:50 Orithyia kernel: [83369.718919] usb 1-1.5.2: New USB device strings: Mfr=1, Product=2, SerialNumber=0 Oct 26 16:15:50 Orithyia kernel: [83369.718921] usb 1-1.5.2: Product: USB Gaming Mouse Oct 26 16:15:50 Orithyia kernel: [83369.718924] usb 1-1.5.2: Manufacturer: Holtek Oct 26 16:15:50 Orithyia kernel: [83369.722486] input: Holtek USB Gaming Mouse as /devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.5/1-1.5.2/1-1.5.2:1.0/input/input13 Oct 26 16:15:50 Orithyia kernel: [83369.722786] hid-generic 0003:04D9:A081.0004: input,hidraw3: USB HID v1.10 Keyboard [Holtek USB Gaming Mouse] on usb-0000:00:1a.0-1.5.2/input0 Oct 26 16:15:50 Orithyia kernel: [83369.729362] hid-generic 0003:04D9:A081.0005: usage index exceeded Oct 26 16:15:50 Orithyia kernel: [83369.729366] hid-generic 0003:04D9:A081.0005: item 0 2 2 2 parsing failed Oct 26 16:15:50 Orithyia kernel: [83369.729379] hid-generic: probe of 0003:04D9:A081.0005 failed with error -22 Oct 26 16:15:50 Orithyia kernel: [83369.731759] hid-generic 0003:04D9:A081.0006: hiddev0,hidraw4: USB HID v1.10 Device [Holtek USB Gaming Mouse] on usb-0000:00:1a.0-1.5.2/input2 Oct 26 16:15:50 Orithyia mtp-probe: checking bus 1, device 6: "/sys/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.5/1-1.5.2" Oct 26 16:15:50 Orithyia mtp-probe: bus: 1, device: 6 was not an MTP device So, I see it did see it is a mouse... but the cursor doesn't move when I move the mouse. Not sure where to debug from here.

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• Why am I getting [mount error(22): Invalid argument] while trying to mount SMB network drive?

  - by Steve_

  Disclaimer: I am very new to Linux :) Anyway, onward: I have a fresh instance of Ubuntu Server (12.04.1 LTS) running on my network and I want to mount a network drive to the server so I can access the contents. The network drive is a SAMBA compatible drive running Darwin OS. If I run the following command: smbclient -L //192.168.0.2 -U myuser It prompts me for the password and then displays output similar to: Domain=[SERVER01] OS=[Darwin] Server=[@(#)PROGRAM:smbd PROJECT:smbx-105.4.0] Sharename Type Comment --------- ---- ------- Comp Staff's Public Folder Disk CompRaid03 Disk Dropbox Disk Groups Disk IPC$ IPC Public Disk Users Disk compstaff Disk However, when I try and mount the CompRaid03 share, using this command: sudo mount -t cifs //192.168.0.2/CompRaid03 /mnt/myshare -o username=myuser I get the same password prompt, but after putting the correct password in, I received this error: mount error(22): Invalid argument dmesg | tail returns: [23576.037373] CIFS VFS: cifs_mount failed w/return code = -22 I don't understand what is wrong with this command. I've managed to mount a share on my current (Windows 8) machine using basically the same command but with a different IP address and share name (obviously). I've spent a good few hours trying to solve this and got no where. Any help or pointers would be greatly appreciated. Thanks Steve EDIT As suggested I've also trued using "user=" instead of "username=": sudo mount -t cifs //192.168.0.2/CompRaid03 /mnt/svnrepo -o user=myuser This results in the same "Invalid argument" error.

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• Is this a good implementation of a loop in Prolog?

  - by Carles Araguz

  First of all, let me tell you that this happens to be the first time I ask something here, so if it's not the right place to do so, please forgive me. I'm developing a rather complex software that has a Prolog core implementing a FSM. Since I don't want it to stop (ever), I'm trying to write a good loop-like predicate that would work using Prolog's recursion. After a few unsuccessful tries (mainly because of stack problems) I ended up having something similar to this: /* Finite State Transition Network */ transition(st0,evnt0,st1). transition(st1,evnt1,st2). transition(st2,evnt2,st0). fsm_state(state(st0),system(Energy,ActivePayloads),[]) :- /* ... */ transition(st0,evnt0,NextState), !, fsm_state(state(NextState),system(Energy,ActivePayloads),[]). fsm_state(state(st1),system(Energy,ActivePayloads),[]) :- /* ... */ transition(st1,evnt1,NextState), !, fsm_state(state(NextState),system(Energy,ActivePayloads),[0,1,2]). fsm_state(state(st2),system(Energy,ActivePayloads),[P|Params]) :- /* ... */ transition(st2,evnt2,NextState), !, fsm_state(state(NextState),system(Energy,ActivePayloads),[]). start :- Sys = system(10,[]), fsm_state(state(s0),Sys,[]). Is this a good approach?

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• software to view logs on remote server

  - by Tarun

  I have configured syslog server on my linux machine like this Linux Machine (syslog client) -- Linux Machine (syslog server) I have configured it and its working properly. Now, the problem is I want to look at the logs located on remote server in a particular directory for example /var/log/host-ip/httpd.log. One way is that I use ssh for that and then see those logs using commands like tail etc. So is there any Browser based graphical utility which I can use on my machine in which I just give the remote folder location, ip-address etc. and the software shows me the logs present on that remote server. Thanks.

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• Barnyard Service - MySQL Error

  - by SLYN

  I installed barnyard2 and saved as a service. When I run service barnyard2 start, Barnyard2 is failed. After I run tail -100 /var/log/messages and I encounter a fault like this. ERROR database: 'mysql' support is not compiled into this build of snort#012 Aug 22 11:52:06 barnyard2[25771]: FATAL ERROR: If this build of barnyard2 was obtained as a binary distribution (e.g., rpm,#012or Windows), then check for alternate builds that contains the necessary#012'mysql' support.#012#012If this build of barnyard2 was compiled by you, then re-run the#012the ./configure script using the '--with-mysql' switch.#012For non-standard installations of a database, the '--with-mysql=DIR'#012syntax may need to be used to specify the base directory of the DB install.#012#012See the database documentation for cursory details (doc/README.database).#012and the URL to the most recent database plugin documentation. Aug 22 11:52:06 barnyard2[25771]: Barnyard2 exiting What sould I do for solving this problem? When I installed Barnyard2, I used these commands: # ./configure --with-mysql --with-mysql-libraries=/usr/lib64/mysql # make ; make install (My System is CentOS 6.5 x86_64.)

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• How do I copy ACLs on Mac OS X?

  - by MagerValp

  Most unix derivates can copy ACLs from one file to another with: getfacl filename1 | setfacl -f - filename2 Unfortunately Mac OS X does not have the getfacl and setfacl commands, as they have rolled ACL handling into chmod. chmod -E accepts a list of ACLs on stdin, but I haven't found a command that will spit out ACLs in a suitable format on stdout. The best I have come up with is: ls -led filename1 | tail +2 | sed 's/^ *[0-9][0-9]*: *//' | chmod -E filename2 Is there a more robust solution? Bonus question: is there a nice way to do it in Python, without using any modules that aren't shipped with 10.6?

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• how to recover data from my disk - I accidentally copied with dd an iso on it

  - by sijoune

  I wanted to create a bootable usb from an iso image and i accidentally put as the output of the dd, instead of my usb drive, one of my hard disks. The iso was 3,3 GB and my disk is 1TB! And it was almost full. Can i at least restore the data that has not been overwritten? Right now i can't even mount it. I get this error: Error mounting /dev/sdd1 at /media/main/UDF Volume: Command-line `mount -t "udf" -o "uhelper=udisks2,nodev,nosuid,uid=1000,gid=1000,iocharset=utf8,umask=0077" "/dev/sdd1" "/media/main/UDF Volume"' exited with non-zero exit status 32: mount: wrong fs type, bad option, bad superblock on /dev/sdd1, missing codepage or helper program, or other error In some cases useful info is found in syslog - try dmesg | tail or so Also since i know which filesystem my disk used if i reformat it to this filesystem is there any chance i can mount it and retrieve the rest of the files?

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• Network randomly drops

  - by user147661

  I have a VPS, ubuntu server 12.04 and for unknown reasons the network connection drops and I have to access my vps via the console and ifdown eth0 and ifup eth0. This brings the connection back up from about a few seconds to a few hours. I have run tail -F /var/log/syslog to monitor the log to see what happens at the point of drop and there is nothing unusual. The vps is running under virt-manager and the hardware is set to virtio. I have had linux friends look at my vps and they are unsure of what is the cause.

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• dynatree: how can i select child node programmatically

  - by Muhammad Adeel Zahid

  hello everyone i m using jquery's dynaTree in my application and i want to select the all the child nodes programmably when a node is selected. the structure of my tree is as follows <div id = "tree"> <ul> <li>package 1 <ul> <li>module 1.1 <ul> <li> document 1.1.1</li> <li> document 1.1.2</li> </ul> </li> <li>module 1.2 <ul> <li>document 1.2.1</li> <li>document 1.2.2</li> </ul> </li> </ul> </li> <li> package 2 <ul> <li> module 2.1 <ul> <li>document 2.1.1</li> <li>document 2.1.1</li> </ul> </li> </ul> </li> </ul> </div> now what i want is that when i click on tree node with title "package 1" all its child nodes i.e (module 1.1, document 1.1.1, document 1.1.2, module 1.2, document 1.2.1, document 1.2.2) should also be selected below is the approach i tried to use $("#tree").dynatree({ onSelect: function(flag, dtnode) { // This will happen each time a check box is selected/deselected var selectedNodes = dtnode.tree.getSelectedNodes(); var selectedKeys = $.map(selectedNodes, function(node) { //alert(node.data.key); return node.data.key; }); // Set the hidden input field's value to the selected items $('#SelectedItems').val(selectedKeys.join(",")); if (flag) { child = dtnode.childList; alert(child.length); for (i = 0; i < child.length; i++) { var x = child[i].select(true); alert(i); } } }, checkbox: true, onActivate: function(dtnode) { //alert("You activated " + dtnode.data.key); } }); in the if(flag) condition i get all the child nodes of element that is selected by user and it gives me the correct value that i can see from alert(child.length) statement. then i run the loop to select all the children but loop never goes beyond the statement var x = child[i].select(true); and i can never see the statement alert(i) being executed. the result of above statement is that if i select package 1, module 1.1 and document 1.1.1 is also selected but never does it execute alert(i) statement neither other children of package 1 are selected. in my view when first time child[i].select(true) statement is executed it also triggers the on select event of its children thus making a recursion kind of thing is my thinking correct? no matter recursion or what why on earth does it not complete the loop and execute very next instruction alert(i). please help me in solving this problem. i m dying to see that alert any suggestion and help is highly appriciated thanks Adeel

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• Core Data - JSON (TouchJSON) on iPhone

  - by Urizen

  I have the following code which seems to go on indefinitely until the app crashes. It seems to happen with the recursion in the datastructureFromManagedObject method. I suspect that this method: 1) looks at the first managed object and follows any relationship property recursively. 2) examines the object at the other end of the relationship found at point 1 and repeats the process. Is it possible that if managed object A has a to-many relationship with object B and that relationship is two-way (i.e an inverse to-one relationship to A from B - e.g. one department has many employees but each employee has only one department) that the following code gets stuck in infinite recursion as it follows the to-one relationship from object B back to object A and so on. If so, can anyone provide a fix for this so that I can get my whole object graph of managed objects converted to JSON. #import "JSONUtils.h" @implementation JSONUtils - (NSDictionary*)dataStructureFromManagedObject:(NSManagedObject *)managedObject { NSDictionary *attributesByName = [[managedObject entity] attributesByName]; NSDictionary *relationshipsByName = [[managedObject entity] relationshipsByName]; //getting the values correspoinding to the attributes collected in attributesByName NSMutableDictionary *valuesDictionary = [[managedObject dictionaryWithValuesForKeys:[attributesByName allKeys]] mutableCopy]; //sets the name for the entity being encoded to JSON [valuesDictionary setObject:[[managedObject entity] name] forKey:@"ManagedObjectName"]; NSLog(@"+++++++++++++++++> before the for loop"); //looks at each relationship for the given managed object for (NSString *relationshipName in [relationshipsByName allKeys]) { NSLog(@"The relationship name = %@",relationshipName); NSRelationshipDescription *description = [relationshipsByName objectForKey:relationshipName]; if (![description isToMany]) { NSLog(@"The relationship is NOT TO MANY!"); [valuesDictionary setObject:[self dataStructureFromManagedObject:[managedObject valueForKey:relationshipName]] forKey:relationshipName]; continue; } NSSet *relationshipObjects = [managedObject valueForKey:relationshipName]; NSMutableArray *relationshipArray = [[NSMutableArray alloc] init]; for (NSManagedObject *relationshipObject in relationshipObjects) { [relationshipArray addObject:[self dataStructureFromManagedObject:relationshipObject]]; } [valuesDictionary setObject:relationshipArray forKey:relationshipName]; } return [valuesDictionary autorelease]; } - (NSArray*)dataStructuresFromManagedObjects:(NSArray*)managedObjects { NSMutableArray *dataArray = [[NSArray alloc] init]; for (NSManagedObject *managedObject in managedObjects) { [dataArray addObject:[self dataStructureFromManagedObject:managedObject]]; } return [dataArray autorelease]; } //method to call for obtaining JSON structure - i.e. public interface to this class - (NSString*)jsonStructureFromManagedObjects:(NSArray*)managedObjects { NSLog(@"-------------> just before running the recursive method"); NSArray *objectsArray = [self dataStructuresFromManagedObjects:managedObjects]; NSLog(@"-------------> just before running the serialiser"); NSString *jsonString = [[CJSONSerializer serializer] serializeArray:objectsArray]; return jsonString; } - (NSManagedObject*)managedObjectFromStructure:(NSDictionary*)structureDictionary withManagedObjectContext:(NSManagedObjectContext*)moc { NSString *objectName = [structureDictionary objectForKey:@"ManagedObjectName"]; NSManagedObject *managedObject = [NSEntityDescription insertNewObjectForEntityForName:objectName inManagedObjectContext:moc]; [managedObject setValuesForKeysWithDictionary:structureDictionary]; for (NSString *relationshipName in [[[managedObject entity] relationshipsByName] allKeys]) { NSRelationshipDescription *description = [[[managedObject entity]relationshipsByName] objectForKey:relationshipName]; if (![description isToMany]) { NSDictionary *childStructureDictionary = [structureDictionary objectForKey:relationshipName]; NSManagedObject *childObject = [self managedObjectFromStructure:childStructureDictionary withManagedObjectContext:moc]; [managedObject setValue:childObject forKey:relationshipName]; continue; } NSMutableSet *relationshipSet = [managedObject mutableSetValueForKey:relationshipName]; NSArray *relationshipArray = [structureDictionary objectForKey:relationshipName]; for (NSDictionary *childStructureDictionary in relationshipArray) { NSManagedObject *childObject = [self managedObjectFromStructure:childStructureDictionary withManagedObjectContext:moc]; [relationshipSet addObject:childObject]; } } return managedObject; } //method to call for obtaining managed objects from JSON structure - i.e. public interface to this class - (NSArray*)managedObjectsFromJSONStructure:(NSString *)json withManagedObjectContext:(NSManagedObjectContext*)moc { NSError *error = nil; NSArray *structureArray = [[CJSONDeserializer deserializer] deserializeAsArray:[json dataUsingEncoding:NSUTF32BigEndianStringEncoding] error:&error]; NSAssert2(error == nil, @"Failed to deserialize\n%@\n%@", [error localizedDescription], json); NSMutableArray *objectArray = [[NSMutableArray alloc] init]; for (NSDictionary *structureDictionary in structureArray) { [objectArray addObject:[self managedObjectFromStructure:structureDictionary withManagedObjectContext:moc]]; } return [objectArray autorelease]; } @end

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• Defend PHP; convince me it isn't horrible

  - by Jason L

  I made a tongue-in-cheek comment in another question thread calling PHP a terrible language and it got down-voted like crazy. Apparently there are lots of people here who love PHP. So I'm genuinely curious. What am I missing? What makes PHP a good language? Here are my reasons for disliking it: PHP has inconsistent naming of built-in and library functions. Predictable naming patterns are important in any design. PHP has inconsistent parameter ordering of built-in functions, eg array_map vs. array_filter which is annoying in the simple cases and raises all sorts of unexpected behaviour or worse. The PHP developers constantly deprecate built-in functions and lower-level functionality. A good example is when they deprecated pass-by-reference for functions. This created a nightmare for anyone doing, say, function callbacks. A lack of consideration in redesign. The above deprecation eliminated the ability to, in many cases, provide default keyword values for functions. They fixed this in PHP 5, but they deprecated the pass-by-reference in PHP 4! Poor execution of name spaces (formerly no name spaces at all). Now that name spaces exist, what do we use as the dereference character? Backslash! The character used universally for escaping, even in PHP! Overly-broad implicit type conversion leads to bugs. I have no problem with implicit conversions of, say, float to integer or back again. But PHP (last I checked) will happily attempt to magically convert an array to an integer. Poor recursion performance. Recursion is a fundamentally important tool for writing in any language; it can make complex algorithms far simpler. Poor support is inexcusable. Functions are case insensitive. I have no idea what they were thinking on this one. A programming language is a way to specify behavior to both a computer and a reader of the code without ambiguity. Case insensitivity introduces much ambiguity. PHP encourages (practically requires) a coupling of processing with presentation. Yes, you can write PHP that doesn't do so, but it's actually easier to write code in the incorrect (from a sound design perspective) manner. PHP performance is abysmal without caching. Does anyone sell a commercial caching product for PHP? Oh, look, the designers of PHP do. Worst of all, PHP convinces people that designing web applications is easy. And it does indeed make much of the effort involved much easier. But the fact is, designing a web application that is both secure and efficient is a very difficult task. By convincing so many to take up programming, PHP has taught an entire subgroup of programmers bad habits and bad design. It's given them access to capabilities that they lack the understanding to use safely. This has led to PHP's reputation as being insecure. (However, I will readily admit that PHP is no more or less secure than any other web programming language.) What is it that I'm missing about PHP? I'm seeing an organically-grown, poorly-managed mess of a language that's spawning poor programmers. So convince me otherwise!

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• Dual booting on separate hard drives

  - by tornadorider

  I have windows XP professional installed on 1 hard drive and Ubuntu 10.10 on my second hard drive. On start up the computer completely skips the grub menu and boots straight into 10.10. I have tried running os-prober with the windows hard drive mounted and then updating grub but it didnt work. Any ideas? I have changed the boot order so that the HDD with xp on it is first however the computer still booted into linux. I tried running grub-install /dev/sda and got this /usr/sbin/grub-setup: warn: Sector 32 is already in use by FlexNet; avoiding it. This software may cause boot or other problems in future. Please ask its authors not to store data in the boot track.. /usr/sbin/grub-setup: warn: Sector 33 is already in use by FlexNet; avoiding it. This software may cause boot or other problems in future. Please ask its authors not to store data in the boot track.. Installation finished. No error reported I checked using disk utility and the code for my xp hard drive is sdb so i ran the camand grub-install /dev/sdb shich gave me this Installation finished. No error reported. So i rebooted but it still didnt work. Any other ideas? Additional info gedit /boot/grub/grub.cfg: # # DO NOT EDIT THIS FILE # # It is automatically generated by grub-mkconfig using templates # from /etc/grub.d and settings from /etc/default/grub # ### BEGIN /etc/grub.d/00_header ### if [ -s $prefix/grubenv ]; then set have_grubenv=true load_env fi set default="0" if [ "${prev_saved_entry}" ]; then set saved_entry="${prev_saved_entry}" save_env saved_entry set prev_saved_entry= save_env prev_saved_entry set boot_once=true fi function savedefault { if [ -z "${boot_once}" ]; then saved_entry="${chosen}" save_env saved_entry fi } function recordfail { set recordfail=1 if [ -n "${have_grubenv}" ]; then if [ -z "${boot_once}" ]; then save_env recordfail; fi; fi } function load_video { insmod vbe insmod vga } insmod part_msdos insmod ext2 set root='(hd0,msdos1)' search --no-floppy --fs-uuid --set d682c9bd-dd89-4827-9802-a1f921ebe21c if loadfont /usr/share/grub/unicode.pf2 ; then set gfxmode=640x480 load_video insmod gfxterm fi terminal_output gfxterm insmod part_msdos insmod ext2 set root='(hd0,msdos1)' search --no-floppy --fs-uuid --set d682c9bd-dd89-4827-9802-a1f921ebe21c set locale_dir=($root)/boot/grub/locale set lang=en insmod gettext if [ "${recordfail}" = 1 ]; then set timeout=-1 else set timeout=10 fi ### END /etc/grub.d/00_header ### ### BEGIN /etc/grub.d/05_debian_theme ### set menu_color_normal=white/black set menu_color_highlight=black/light-gray ### END /etc/grub.d/05_debian_theme ### ### BEGIN /etc/grub.d/10_linux ### menuentry 'Ubuntu, with Linux 2.6.35-28-generic' --class ubuntu --class gnu-linux --class gnu --class os { recordfail insmod part_msdos insmod ext2 set root='(hd0,msdos1)' search --no-floppy --fs-uuid --set d682c9bd-dd89-4827-9802-a1f921ebe21c linux /boot/vmlinuz-2.6.35-28-generic root=UUID=d682c9bd-dd89-4827-9802-a1f921ebe21c ro quiet splash initrd /boot/initrd.img-2.6.35-28-generic } menuentry 'Ubuntu, with Linux 2.6.35-28-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os { recordfail insmod part_msdos insmod ext2 set root='(hd0,msdos1)' search --no-floppy --fs-uuid --set d682c9bd-dd89-4827-9802-a1f921ebe21c echo 'Loading Linux 2.6.35-28-generic ...' linux /boot/vmlinuz-2.6.35-28-generic root=UUID=d682c9bd-dd89-4827-9802-a1f921ebe21c ro single echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-2.6.35-28-generic } menuentry 'Ubuntu, with Linux 2.6.35-22-generic' --class ubuntu --class gnu-linux --class gnu --class os { recordfail insmod part_msdos insmod ext2 set root='(hd0,msdos1)' search --no-floppy --fs-uuid --set d682c9bd-dd89-4827-9802-a1f921ebe21c linux /boot/vmlinuz-2.6.35-22-generic root=UUID=d682c9bd-dd89-4827-9802-a1f921ebe21c ro quiet splash initrd /boot/initrd.img-2.6.35-22-generic } menuentry 'Ubuntu, with Linux 2.6.35-22-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os { recordfail insmod part_msdos insmod ext2 set root='(hd0,msdos1)' search --no-floppy --fs-uuid --set d682c9bd-dd89-4827-9802-a1f921ebe21c echo 'Loading Linux 2.6.35-22-generic ...' linux /boot/vmlinuz-2.6.35-22-generic root=UUID=d682c9bd-dd89-4827-9802-a1f921ebe21c ro single echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-2.6.35-22-generic } ### END /etc/grub.d/10_linux ### ### BEGIN /etc/grub.d/20_linux_xen ### ### END /etc/grub.d/20_linux_xen ### ### BEGIN /etc/grub.d/20_memtest86+ ### menuentry "Memory test (memtest86+)" { insmod part_msdos insmod ext2 set root='(hd0,msdos1)' search --no-floppy --fs-uuid --set d682c9bd-dd89-4827-9802-a1f921ebe21c linux16 /boot/memtest86+.bin } menuentry "Memory test (memtest86+, serial console 115200)" { insmod part_msdos insmod ext2 set root='(hd0,msdos1)' search --no-floppy --fs-uuid --set d682c9bd-dd89-4827-9802-a1f921ebe21c linux16 /boot/memtest86+.bin console=ttyS0,115200n8 } ### END /etc/grub.d/20_memtest86+ ### ### BEGIN /etc/grub.d/30_os-prober ### if [ "x${timeout}" != "x-1" ]; then if keystatus; then if keystatus --shift; then set timeout=-1 else set timeout=0 fi else if sleep --interruptible 3 ; then set timeout=0 fi fi fi ### END /etc/grub.d/30_os-prober ### ### BEGIN /etc/grub.d/40_custom ### # This file provides an easy way to add custom menu entries. Simply type the # menu entries you want to add after this comment. Be careful not to change # the 'exec tail' line above. ### END /etc/grub.d/40_custom ### ### BEGIN /etc/grub.d/41_custom ### if [ -f $prefix/custom.cfg ]; then source $prefix/custom.cfg; fi ### END /etc/grub.d/41_custom ### sudo fdisk -l: Disk /dev/sda: 80.1 GB, 80060424192 bytes 255 heads, 63 sectors/track, 9733 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x0008a483 Device Boot Start End Blocks Id System /dev/sda1 * 1 9352 75112448 83 Linux /dev/sda2 9352 9734 3068929 5 Extended /dev/sda5 9352 9734 3068928 82 Linux swap / Solaris Disk /dev/sdb: 500.1 GB, 500107862016 bytes 255 heads, 63 sectors/track, 60801 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0xc5d6c5d6 Device Boot Start End Blocks Id System /dev/sdb1 1 60800 488375968+ 7 HPFS/NTFS sudo blkid /dev/sda1: UUID="d682c9bd-dd89-4827-9802-a1f921ebe21c" TYPE="ext4" /dev/sda5: UUID="09e9c2cb-d903-4f0b-a181-536951845231" TYPE="swap" /dev/sdb1: UUID="B21844EB1844AFE1" TYPE="ntfs" sudo os-prober (nothing) Boot Info Script 0.55 dated February 15th, 2010 ============================= Boot Info Summary: ============================== => Grub 2 is installed in the MBR of /dev/sda and looks on the same drive in partition #1 for (,msdos1)/boot/grub. => Grub 2 is installed in the MBR of /dev/sdb and looks on the same drive in partition #1 for (,msdos1)/boot/grub. sda1: _________________________________________________________________________ File system: ext4 Boot sector type: - Boot sector info: Operating System: Ubuntu 10.10 Boot files/dirs: /boot/grub/grub.cfg /etc/fstab /boot/grub/core.img sda2: _________________________________________________________________________ File system: Extended Partition Boot sector type: Unknown Boot sector info: sda5: _________________________________________________________________________ File system: swap Boot sector type: - Boot sector info: sdb1: _________________________________________________________________________ File system: ntfs Boot sector type: Windows XP Boot sector info: No errors found in the Boot Parameter Block. Operating System: Windows XP Boot files/dirs: =========================== Drive/Partition Info: ============================= Drive: sda ___________________ _____________________________________________________ Disk /dev/sda: 80.1 GB, 80060424192 bytes 255 heads, 63 sectors/track, 9733 cylinders, total 156368016 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes Partition Boot Start End Size Id System /dev/sda1 * 2,048 150,226,943 150,224,896 83 Linux /dev/sda2 150,228,990 156,366,847 6,137,858 5 Extended /dev/sda5 150,228,992 156,366,847 6,137,856 82 Linux swap / Solaris Drive: sdb ___________________ _____________________________________________________ Disk /dev/sdb: 500.1 GB, 500107862016 bytes 255 heads, 63 sectors/track, 60801 cylinders, total 976773168 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes Partition Boot Start End Size Id System /dev/sdb1 * 63 976,751,999 976,751,937 7 HPFS/NTFS blkid -c /dev/null: ____________________________________________________________ Device UUID TYPE LABEL /dev/sda1 d682c9bd-dd89-4827-9802-a1f921ebe21c ext4 /dev/sda2: PTTYPE="dos" /dev/sda5 09e9c2cb-d903-4f0b-a181-536951845231 swap /dev/sda: PTTYPE="dos" /dev/sdb1 B21844EB1844AFE1 ntfs /dev/sdb: PTTYPE="dos" ============================ "mount | grep ^/dev output: =========================== Device Mount_Point Type Options /dev/sda1 / ext4 (rw,errors=remount-ro,commit=0) =========================== sda1/boot/grub/grub.cfg: =========================== # # DO NOT EDIT THIS FILE # # It is automatically generated by grub-mkconfig using templates # from /etc/grub.d and settings from /etc/default/grub # ### BEGIN /etc/grub.d/00_header ### if [ -s $prefix/grubenv ]; then set have_grubenv=true load_env fi set default="0" if [ "${prev_saved_entry}" ]; then set saved_entry="${prev_saved_entry}" save_env saved_entry set prev_saved_entry= save_env prev_saved_entry set boot_once=true fi function savedefault { if [ -z "${boot_once}" ]; then saved_entry="${chosen}" save_env saved_entry fi } function recordfail { set recordfail=1 if [ -n "${have_grubenv}" ]; then if [ -z "${boot_once}" ]; then save_env recordfail; fi; fi } function load_video { insmod vbe insmod vga } insmod part_msdos insmod ext2 set root='(hd0,msdos1)' search --no-floppy --fs-uuid --set d682c9bd-dd89-4827-9802-a1f921ebe21c if loadfont /usr/share/grub/unicode.pf2 ; then set gfxmode=640x480 load_video insmod gfxterm fi terminal_output gfxterm insmod part_msdos insmod ext2 set root='(hd0,msdos1)' search --no-floppy --fs-uuid --set d682c9bd-dd89-4827-9802-a1f921ebe21c set locale_dir=($root)/boot/grub/locale set lang=en insmod gettext if [ "${recordfail}" = 1 ]; then set timeout=-1 else set timeout=10 fi ### END /etc/grub.d/00_header ### ### BEGIN /etc/grub.d/05_debian_theme ### set menu_color_normal=white/black set menu_color_highlight=black/light-gray ### END /etc/grub.d/05_debian_theme ### ### BEGIN /etc/grub.d/10_linux ### menuentry 'Ubuntu, with Linux 2.6.35-28-generic' --class ubuntu --class gnu-linux --class gnu --class os { recordfail insmod part_msdos insmod ext2 set root='(hd0,msdos1)' search --no-floppy --fs-uuid --set d682c9bd-dd89-4827-9802-a1f921ebe21c linux /boot/vmlinuz-2.6.35-28-generic root=UUID=d682c9bd-dd89-4827-9802-a1f921ebe21c ro quiet splash initrd /boot/initrd.img-2.6.35-28-generic } menuentry 'Ubuntu, with Linux 2.6.35-28-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os { recordfail insmod part_msdos insmod ext2 set root='(hd0,msdos1)' search --no-floppy --fs-uuid --set d682c9bd-dd89-4827-9802-a1f921ebe21c echo 'Loading Linux 2.6.35-28-generic ...' linux /boot/vmlinuz-2.6.35-28-generic root=UUID=d682c9bd-dd89-4827-9802-a1f921ebe21c ro single echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-2.6.35-28-generic } menuentry 'Ubuntu, with Linux 2.6.35-22-generic' --class ubuntu --class gnu-linux --class gnu --class os { recordfail insmod part_msdos insmod ext2 set root='(hd0,msdos1)' search --no-floppy --fs-uuid --set d682c9bd-dd89-4827-9802-a1f921ebe21c linux /boot/vmlinuz-2.6.35-22-generic root=UUID=d682c9bd-dd89-4827-9802-a1f921ebe21c ro quiet splash initrd /boot/initrd.img-2.6.35-22-generic } menuentry 'Ubuntu, with Linux 2.6.35-22-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os { recordfail insmod part_msdos insmod ext2 set root='(hd0,msdos1)' search --no-floppy --fs-uuid --set d682c9bd-dd89-4827-9802-a1f921ebe21c echo 'Loading Linux 2.6.35-22-generic ...' linux /boot/vmlinuz-2.6.35-22-generic root=UUID=d682c9bd-dd89-4827-9802-a1f921ebe21c ro single echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-2.6.35-22-generic } ### END /etc/grub.d/10_linux ### ### BEGIN /etc/grub.d/20_linux_xen ### ### END /etc/grub.d/20_linux_xen ### ### BEGIN /etc/grub.d/20_memtest86+ ### menuentry "Memory test (memtest86+)" { insmod part_msdos insmod ext2 set root='(hd0,msdos1)' search --no-floppy --fs-uuid --set d682c9bd-dd89-4827-9802-a1f921ebe21c linux16 /boot/memtest86+.bin } menuentry "Memory test (memtest86+, serial console 115200)" { insmod part_msdos insmod ext2 set root='(hd0,msdos1)' search --no-floppy --fs-uuid --set d682c9bd-dd89-4827-9802-a1f921ebe21c linux16 /boot/memtest86+.bin console=ttyS0,115200n8 } ### END /etc/grub.d/20_memtest86+ ### ### BEGIN /etc/grub.d/30_os-prober ### if [ "x${timeout}" != "x-1" ]; then if keystatus; then if keystatus --shift; then set timeout=-1 else set timeout=0 fi else if sleep --interruptible 3 ; then set timeout=0 fi fi fi ### END /etc/grub.d/30_os-prober ### ### BEGIN /etc/grub.d/40_custom ### # This file provides an easy way to add custom menu entries. Simply type the # menu entries you want to add after this comment. Be careful not to change # the 'exec tail' line above. menuentry "Windows XP" { set root=(hd1,1) chainloader (hd1,1)+1 } ### END /etc/grub.d/40_custom ### ### BEGIN /etc/grub.d/41_custom ### if [ -f $prefix/custom.cfg ]; then source $prefix/custom.cfg; fi ### END /etc/grub.d/41_custom ### =============================== sda1/etc/fstab: =============================== # /etc/fstab: static file system information. # # Use 'blkid -o value -s UUID' to print the universally unique identifier # for a device; this may be used with UUID= as a more robust way to name # devices that works even if disks are added and removed. See fstab(5). # # <file system> <mount point> <type> <options> <dump> <pass> proc /proc proc nodev,noexec,nosuid 0 0 /dev/sda1 / ext4 errors=remount-ro 0 1 # swap was on /dev/sda5 during installation UUID=09e9c2cb-d903-4f0b-a181-536951845231 none swap sw 0 0 =================== sda1: Location of files loaded by Grub: =================== 51.7GB: boot/grub/core.img 58.5GB: boot/grub/grub.cfg 1.2GB: boot/initrd.img-2.6.35-22-generic 1.3GB: boot/initrd.img-2.6.35-28-generic 58.2GB: boot/vmlinuz-2.6.35-22-generic 51.7GB: boot/vmlinuz-2.6.35-28-generic 1.3GB: initrd.img 1.2GB: initrd.img.old 51.7GB: vmlinuz 58.2GB: vmlinuz.old =========================== Unknown MBRs/Boot Sectors/etc ======================= Unknown BootLoader on sda2 00000000 d9 ed 13 ab ff a8 33 8c 01 b2 47 99 e1 4a b1 f1 |......3...G..J..| 00000010 69 5f a7 29 a4 1a 03 9e 31 b9 45 02 71 e6 58 78 |i_.)....1.E.q.Xx| 00000020 3d f6 ee 7b 3e 33 1b 82 c6 7d cf 1a c8 e7 bc 2f |=..{>3...}...../| 00000030 b9 e1 70 75 cf 18 aa e7 d5 7e 3c f1 b4 e7 9e 3a |..pu.....~<....:| 00000040 55 38 f1 b4 ee 78 59 0b 5e f7 3c 4c 57 73 9c 2a |U8...xY.^.<LWs.*| 00000050 28 f1 19 ed 11 9c b2 19 e2 80 92 1c 7b 84 ee 0b |(...........{...| 00000060 e2 c0 ac af 0a 50 42 b9 cf 0c dc 2c 20 77 85 dc |.....PB...., w..| 00000070 8f 70 5f 7b 84 9b a1 f7 8c 2d ee 70 5c ae f7 39 |.p_{.....-.p\..9| 00000080 63 f7 09 8a ec 79 4c ed 9f cc ad 3c f8 1b 47 7d |c....yL....<..G}| 00000090 3f 97 d5 16 cb 29 45 38 25 61 36 08 de 10 93 0f |?....)E8%a6.....| 000000a0 95 4f ea 54 f9 89 ff f1 bf 9a cc bb fd b6 22 b1 |.O.T..........".| 000000b0 65 08 05 21 78 19 46 b0 24 7e fb de d4 b3 ba d6 |e..!x.F.$~......| 000000c0 ec 11 65 82 ee 10 1d 12 04 91 da 6d 67 47 ea 9b |..e........mgG..| 000000d0 6f b0 aa fb cb 67 10 64 86 e8 26 85 fb f9 50 77 |o....g.d..&...Pw| 000000e0 9d 13 9b 9e d9 11 f3 a1 50 1b 11 b7 93 79 9f ab |........P....y..| 000000f0 c1 b6 86 0f 35 ed d4 9f dc f8 db bd ed 45 3a 68 |....5........E:h| 00000100 54 68 4a 1d d1 fc b8 c9 72 b4 d7 7b 60 e7 39 2f |ThJ.....r..{`.9/| 00000110 2a 0a 4e 52 72 52 c6 e2 2a 55 6a 2a e1 82 40 71 |*.NRrR..*Uj*..@q| 00000120 11 11 e0 53 d6 ff 1b a9 c6 65 df 1e b7 15 6f a2 |...S.....e....o.| 00000130 15 02 a4 6d 19 b7 78 57 a6 ee 9e 36 08 7d 6f 7c |...m..xW...6.}o|| 00000140 fd f7 7c d5 40 ff 0f c7 97 dc aa 00 ce 8b bb dc |..|.@...........| 00000150 e2 eb 1c 50 74 d8 14 cc 9a d6 5c a2 ab f2 67 f9 |...Pt.....\...g.| 00000160 58 ed 43 79 0e 78 7a 5c a6 f8 7b e8 05 4e 62 8a |X.Cy.xz\..{..Nb.| 00000170 0a 5f 22 ee a6 38 b9 e1 32 45 97 08 cc 75 66 c6 |._"..8..2E...uf.| 00000180 b3 a2 2d 89 a1 e9 95 21 28 53 fd dd be b1 b2 a2 |..-....!(S......| 00000190 78 3f a3 c9 3d e3 31 54 88 cf 78 0d e1 21 a8 74 |x?..=.1T..x..!.t| 000001a0 06 60 9d 21 c6 7a 24 e1 cc 28 f8 98 e0 99 e3 fc |.`.!.z$..(......| 000001b0 fa 8b eb d5 56 03 20 b8 54 ba c6 ee 9f 57 00 fe |....V. .T....W..| 000001c0 ff ff 82 fe ff ff 02 00 00 00 00 a8 5d 00 00 00 |............]...| 000001d0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 000001f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 55 aa |..............U.| 00000200

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• A jQuery Plug-in to monitor Html Element CSS Changes

  - by Rick Strahl

  Here's a scenario I've run into on a few occasions: I need to be able to monitor certain CSS properties on an HTML element and know when that CSS element changes. The need for this arose out of wanting to build generic components that could 'attach' themselves to other objects and monitor changes on the ‘parent’ object so the dependent object can adjust itself accordingly. What I wanted to create is a jQuery plug-in that allows me to specify a list of CSS properties to monitor and have a function fire in response to any change to any of those CSS properties. The result are the .watch() and .unwatch() jQuery plug-ins. Here’s a simple example page of this plug-in that demonstrates tracking changes to an element being moved with draggable and closable behavior: http://www.west-wind.com/WestWindWebToolkit/samples/Ajax/jQueryPluginSamples/WatcherPlugin.htm Try it with different browsers – IE and FireFox use the DOM event handlers and Chrome, Safari and Opera use setInterval handlers to manage this behavior. It should work in all of them but all but IE and FireFox will show a bit of lag between the changes in the main element and the shadow. The relevant HTML for this example is this fragment of a main <div> (#notebox) and an element that is to mimic a shadow (#shadow). <div class="containercontent"> <div id="notebox" style="width: 200px; height: 150px;position: absolute; z-index: 20; padding: 20px; background-color: lightsteelblue;"> Go ahead drag me around and close me! </div> <div id="shadow" style="background-color: Gray; z-index: 19;position:absolute;display: none;"> </div> </div> The watcher plug in is then applied to the main <div> and shadow in sync with the following plug-in code: <script type="text/javascript"> $(document).ready(function () { var counter = 0; $("#notebox").watch("top,left,height,width,display,opacity", function (data, i) { var el = $(this); var sh = $("#shadow"); var propChanged = data.props[i]; var valChanged = data.vals[i]; counter++; showStatus("Prop: " + propChanged + " value: " + valChanged + " " + counter); var pos = el.position(); var w = el.outerWidth(); var h = el.outerHeight(); sh.css({ width: w, height: h, left: pos.left + 5, top: pos.top + 5, display: el.css("display"), opacity: el.css("opacity") }); }) .draggable() .closable() .css("left", 10); }); </script> When you run this page as you drag the #notebox element the #shadow element will maintain and stay pinned underneath the #notebox element effectively keeping the shadow attached to the main element. Likewise, if you hide or fadeOut() the #notebox element the shadow will also go away – show the #notebox element and the shadow also re-appears because we are assigning the display property from the parent on the shadow. Note we’re attaching the .watch() plug-in to the #notebox element and have it fire whenever top,left,height,width,opacity or display CSS properties are changed. The passed data element contains a props[] and vals[] array that holds the properties monitored and their current values. An index passed as the second parm tells you which property has changed and what its current value is (propChanged/valChanged in the code above). The rest of the watcher handler code then deals with figuring out the main element’s position and recalculating and setting the shadow’s position using the jQuery .css() function. Note that this is just an example to demonstrate the watch() behavior here – this is not the best way to create a shadow. If you’re interested in a more efficient and cleaner way to handle shadows with a plug-in check out the .shadow() plug-in in ww.jquery.js (code search for fn.shadow) which uses native CSS features when available but falls back to a tracked shadow element on browsers that don’t support it, which is how this watch() plug-in came about in the first place :-) How does it work? The plug-in works by letting the user specify a list of properties to monitor as a comma delimited string and a handler function: el.watch("top,left,height,width,display,opacity", function (data, i) {}, 100, id) You can also specify an interval (if no DOM event monitoring isn’t available in the browser) and an ID that identifies the event handler uniquely. The watch plug-in works by hooking up to DOMAttrModified in FireFox, to onPropertyChanged in Internet Explorer, or by using a timer with setInterval to handle the detection of changes for other browsers. Unfortunately WebKit doesn’t support DOMAttrModified consistently at the moment so Safari and Chrome currently have to use the slower setInterval mechanism. In response to a changed property (or a setInterval timer hit) a JavaScript handler is fired which then runs through all the properties monitored and determines if and which one has changed. The DOM events fire on all property/style changes so the intermediate plug-in handler filters only those hits we’re interested in. If one of our monitored properties has changed the specified event handler function is called along with a data object and an index that identifies the property that’s changed in the data.props/data.vals arrays. The jQuery plugin to implement this functionality looks like this: (function($){ $.fn.watch = function (props, func, interval, id) { /// <summary> /// Allows you to monitor changes in a specific /// CSS property of an element by polling the value. /// when the value changes a function is called. /// The function called is called in the context /// of the selected element (ie. this) /// </summary> /// <param name="prop" type="String">CSS Properties to watch sep. by commas</param> /// <param name="func" type="Function"> /// Function called when the value has changed. /// </param> /// <param name="interval" type="Number"> /// Optional interval for browsers that don't support DOMAttrModified or propertychange events. /// Determines the interval used for setInterval calls. /// </param> /// <param name="id" type="String">A unique ID that identifies this watch instance on this element</param> /// <returns type="jQuery" /> if (!interval) interval = 100; if (!id) id = "_watcher"; return this.each(function () { var _t = this; var el$ = $(this); var fnc = function () { __watcher.call(_t, id) }; var data = { id: id, props: props.split(","), vals: [props.split(",").length], func: func, fnc: fnc, origProps: props, interval: interval, intervalId: null }; // store initial props and values $.each(data.props, function (i) { data.vals[i] = el$.css(data.props[i]); }); el$.data(id, data); hookChange(el$, id, data); }); function hookChange(el$, id, data) { el$.each(function () { var el = $(this); if (typeof (el.get(0).onpropertychange) == "object") el.bind("propertychange." + id, data.fnc); else if ($.browser.mozilla) el.bind("DOMAttrModified." + id, data.fnc); else data.intervalId = setInterval(data.fnc, interval); }); } function __watcher(id) { var el$ = $(this); var w = el$.data(id); if (!w) return; var _t = this; if (!w.func) return; // must unbind or else unwanted recursion may occur el$.unwatch(id); var changed = false; var i = 0; for (i; i < w.props.length; i++) { var newVal = el$.css(w.props[i]); if (w.vals[i] != newVal) { w.vals[i] = newVal; changed = true; break; } } if (changed) w.func.call(_t, w, i); // rebind event hookChange(el$, id, w); } } $.fn.unwatch = function (id) { this.each(function () { var el = $(this); var data = el.data(id); try { if (typeof (this.onpropertychange) == "object") el.unbind("propertychange." + id, data.fnc); else if ($.browser.mozilla) el.unbind("DOMAttrModified." + id, data.fnc); else clearInterval(data.intervalId); } // ignore if element was already unbound catch (e) { } }); return this; } })(jQuery); Note that there’s a corresponding .unwatch() plug-in that can be used to stop monitoring properties. The ID parameter is optional both on watch() and unwatch() – a standard name is used if you don’t specify one, but it’s a good idea to use unique names for each element watched to avoid overlap in event ids especially if you’re monitoring many elements. The syntax is: $.fn.watch = function(props, func, interval, id) props A comma delimited list of CSS style properties that are to be watched for changes. If any of the specified properties changes the function specified in the second parameter is fired. func The function fired in response to a changed styles. Receives this as the element changed and an object parameter that represents the watched properties and their respective values. The first parameter is passed in this structure: { id: watcherId, props: [], vals: [], func: thisFunc, fnc: internalHandler, origProps: strPropertyListOnWatcher }; A second parameter is the index of the changed property so data.props[i] or data.vals[i] gets the property and changed value. interval The interval for setInterval() for those browsers that don't support property watching in the DOM. In milliseconds. id An optional id that identifies this watcher. Required only if multiple watchers might be hooked up to the same element. The default is _watcher if not specified. It’s been a Journey I started building this plug-in about two years ago and had to make many modifications to it in response to changes in jQuery and also in browser behaviors. I think the latest round of changes made should make this plug-in fairly future proof going forward (although I hope there will be better cross-browser change event notifications in the future). One of the big problems I ran into had to do with recursive change notifications – it looks like starting with jQuery 1.44 and later, jQuery internally modifies element properties on some calls to some .css()  property retrievals and things like outerHeight/Width(). In IE this would cause nasty lock up issues at times. In response to this I changed the code to unbind the events when the handler function is called and then rebind when it exits. This also makes user code less prone to stack overflow recursion as you can actually change properties on the base element. It also means though that if you change one of the monitors properties in the handler the watch() handler won’t fire in response – you need to resort to a setTimeout() call instead to force the code to run outside of the handler: $("#notebox") el.watch("top,left,height,width,display,opacity", function (data, i) { var el = $(this); … // this makes el changes work setTimeout(function () { el.css("top", 10) },10); }) Since I’ve built this component I’ve had a lot of good uses for it. The .shadow() fallback functionality is one of them. Resources The watch() plug-in is part of ww.jquery.js and the West Wind West Wind Web Toolkit. You’re free to use this code here or the code from the toolkit. West Wind Web Toolkit Latest version of ww.jquery.js (search for fn.watch) watch plug-in documentation © Rick Strahl, West Wind Technologies, 2005-2011Posted in ASP.NET  JavaScript  jQuery  

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• Problems configuring nameserver in plesk

  - by Saif Bechan

  Hello, i have some troubles with setting up a nameserver in PLESK for months now. I have tried all possible scenario's but i can not get this to work. I am really in need for some help, and if you can i will really appreciate it. Basically what i want is to just set up a nameserver in PLESK. I have a primary IP, and my host gave me a secondary nameserver i can use. My host is leaseweb in the netherlands. I have made some screenshots of the important parts in my opinion, maybe you guys can see some errors in them. To use the secondary nameserver provided by leaseweb i had to enable ACL on that account, i did so and made a screenshot of that too. The DNS recursion is set to localnets. These settings have not changed for months, so the dns should be fully updated everywhere. The check i run is the following: https://www.sidn.nl/over-nl/aanvraag...-server-check/ Domeinnaam (inclusief .nl): rdshosting.nl Eerste Nameserver: ns1.rdshosting.nl Eerste IP: 62.212.66.33 Tweede Nameserver: ns7.leaseweb.net Tweede ip: 62.212.76.50 If i run the dns check of the netherlands it gives me the following errors: primary name server "ns1.rdshosting.nl." Error: specified name server is not listed as NS record. All public name servers for a domain must also be listed as NS records in the zone of the domain. This domain was specified explicitly as a name server, but not found in the zone description of the primary name server. TE.6a rdshosting.nl. 86400 IN SOA ns1.rdspartners.nl. saif2k.hotmail.com. (2010031102 12H 1H 7D 3H) Error: the MNAME in SOA says "ns1.rdspartners.nl." is the primary name server. The MNAME field in the SOA record (first parameter) lists a different primary name server from the one specified for this check. RFC1035 section 3.3.13 rdshosting.nl. 86400 IN NS ns1.rdspartners.nl. Warning: hidden name server "ns1.rdspartners.nl." never used for first contact. The zone contains an NS record for a host which is not in the list of specified name servers. Hence, this name server will not be used to initiate contact to the domain. It may be used in sequential lookups, so it may still be useful. secondary name server "ns1.rdspartners.nl." [BROKEN] [HIDDEN] Failure: name server at 77.232.85.129 cannot be reached: (unknown error) The name server could not be contacted, which may be due to temporary technical problems or global DNS configuration mistakes. The internal error is shown, but not always clear about the cause. secondary name server "ns7.leaseweb.net." Info: name server looks correctly configured. I have the content of the file etc/named.conf also: // $Id: named.conf,v 1.1.1.1 2001/10/15 07:44:36 kap Exp $ // // Refer to the named(8) man page for details. If you are ever going // to setup a primary server, make sure you've understood the hairy // details of how DNS is working. Even with simple mistakes, you can // break connectivity for affected parties, or cause huge amount of // useless Internet traffic. options { allow-recursion { localnets; }; directory "/var"; auth-nxdomain no; pid-file "/var/run/named/named.pid"; // In addition to the "forwarders" clause, you can force your name // server to never initiate queries of its own, but always ask its // forwarders only, by enabling the following line: // // forward only; // If you've got a DNS server around at your upstream provider, enter // its IP address here, and enable the line below. This will make you // benefit from its cache, thus reduce overall DNS traffic in the Internet. /* forwarders { 127.0.0.1; }; */ /* * If there is a firewall between you and nameservers you want * to talk to, you might need to uncomment the query-source * directive below. Previous versions of BIND always asked * questions using port 53, but BIND 8.1 uses an unprivileged * port by default. */ // query-source address * port 53; /* * If running in a sandbox, you may have to specify a different * location for the dumpfile. */ // dump-file "s/named_dump.db"; }; //Use with the following in named.conf, adjusting the allow list as needed: key "rndc-key" { algorithm hmac-md5; secret "CeMgS23y0oWE20nyv0x40Q=="; }; controls { inet 127.0.0.1 port 953 allow { 127.0.0.1; } keys { "rndc-key"; }; }; // Note: the following will be supported in a future release. /* host { any; } { topology { 127.0.0.0/8; }; }; */ // Setting up secondaries is way easier and the rough picture for this // is explained below. // // If you enable a local name server, don't forget to enter 127.0.0.1 // into your /etc/resolv.conf so this server will be queried first. // Also, make sure to enable it in /etc/rc.conf. zone "." { type hint; file "named.root"; }; zone "0.0.127.IN-ADDR.ARPA" { type master; file "localhost.rev"; }; // NB: Do not use the IP addresses below, they are faked, and only // serve demonstration/documentation purposes! // // Example secondary config entries. It can be convenient to become // a secondary at least for the zone where your own domain is in. Ask // your network administrator for the IP address of the responsible // primary. // // Never forget to include the reverse lookup (IN-ADDR.ARPA) zone! // (This is the first bytes of the respective IP address, in reverse // order, with ".IN-ADDR.ARPA" appended.) // // Before starting to setup a primary zone, better make sure you fully // understand how DNS and BIND works, however. There are sometimes // unobvious pitfalls. Setting up a secondary is comparably simpler. // // NB: Don't blindly enable the examples below. :-) Use actual names // and addresses instead. // // NOTE!!! FreeBSD runs bind in a sandbox (see named_flags in rc.conf). // The directory containing the secondary zones must be write accessible // to bind. The following sequence is suggested: // // mkdir /etc/namedb/s // chown bind.bind /etc/namedb/s // chmod 750 /etc/namedb/s zone "rdshosting.nl" { type master; file "rdshosting.nl"; allow-transfer { 77.232.85.129; 62.212.76.50; common-allow-transfer; }; }; zone "66.212.62.in-addr.arpa" { type master; file "66.212.62.in-addr.arpa"; allow-transfer { common-allow-transfer; }; }; acl common-allow-transfer { 62.212.76.50; }; As i mentioned i made some screenshots of some parts: First the dns settings in plesk: http://www.freeimagehosting.net/uploads/2480faed5e.jpg Second the acl settings in plesk: http://www.freeimagehosting.net/uploads/777f5e69b0.jpg Third my settings at leaseweb: http://www.freeimagehosting.net/uploads/de7122b19c.jpg And last the secondary nameserver settings from leaseweb: http://www.freeimagehosting.net/uploads/fd1da38a8f.jpg If someone has anysuggestion at all on this this will be highly appriciated. Thank you for your time! PS. I am dutch so dutch answers are welcome aswell

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• help with number calculation algorithm [hw]

  - by sa125

  Hi - I'm working on a hw problem that asks me this: given a finite set of numbers, and a target number, find if the set can be used to calculate the target number using basic math operations (add, sub, mult, div) and using each number in the set exactly once (so I need to exhaust the set). This has to be done with recursion. So, for example, if I have the set {1, 2, 3, 4} and target 10, then I could get to it by using ((3 * 4) - 2)/1 = 10. I'm trying to phrase the algorithm in pseudo-code, but so far haven't gotten too far. I'm thinking graphs are the way to go, but would definitely appreciate help on this. thanks.

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• django admin: Add a "remove file" field for Image- or FileFields

  - by w-

  I was hunting around the net for a way to easily allow users to blank out imagefield/filefields they have set in the admin. I found this http://www.djangosnippets.org/snippets/894/ What was really interesting to me here was the code posted in the comment by rfugger remove_the_file = forms.BooleanField(required=False) def save(self, *args, **kwargs): object = super(self.__class__, self).save(*args, **kwargs) if self.cleaned_data.get('remove_the_file'): object.the_file = '' return object When i try to use this in my own form I basically added this to my admin.py which already had a BlahAdmin class BlahModelForm(forms.ModelForm): class Meta: model = Blah remove_img01 = forms.BooleanField(required=False) def save(self, *args, **kwargs): object = super(self.__class__, self).save(*args, **kwargs) if self.cleaned_data.get('remove_img01'): object.img01 = '' return object when i run it I get this error maximum recursion depth exceeded while calling a Python object at this line object = super(self.__class__, self).save(*args, **kwargs) When i think about it for a bit, it seems obvious that it is just infinitely calling itself causing the error. My problem is i can't figure out what is the correct way i should be doing this. Any suggestions? thanks

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• unrobustive jQuery and rails with ajax and form validation

  - by bogumbiker

  Hello, I am looking for a way to call successfully custom function from submitHandler to do proper ajax post. Here is my custom function: jQuery.fn.submitWithAjax = function() { this.submit(function() { $.post(this.action, $(this).serialize(), null, "script"); return false; }) return this; }; Before using validate plugin I had following which worked fine: $(document).ready(function() { $("#my_form").submitWithAjax(); } Now I have added the validation part and have no idea how to call my custom submitWithAjax function?? $(document).ready(function() { $("#my_form").validate({ /*Validations - works perfectly!! */ }, submitHandler: function(form) { /* $("#my_form").submitWithAjax(); - this works but introduces recursion */ /* how to call custom subitWithAjax() ????? */ } }); }) Thanks!

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• Language Design: Combining Gotos and Functions

  - by sub

  I'm designing and currently rethinking a low-level interpreted programming language with similarities to assembler. I very soon came across the functions/loops/gotos decision problem and thought that while loops like while and for would be too high-level and unfitting, gotos would be too low level, unmaintainable and generally evil again. Functions like you know them from most languages that have return values and arguments aren't fitting in the language's concept either. So I tried to figure out something between a function and a goto which is capable of Recursion Efficient loops After some thinking I came up with the idea of subroutines: They have a beginning and an end like a function They have a name but no arguments like a goto You can go into one with jump and go out of it again before its end with return (doesn't give back any result, only stops the subroutine) Handled just like normal code - Global scope like goto So I wanted to know: Is the idea above good? What are the (dis)advantages? Would there be a better combination of function and goto or even a completely new idea?

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• SElinux process killed while trying to set boolean

  - by Antonio

  I've got a strange problem. I can not allow apache to connect to database at my CentOC 6.4 box: [root@centos6 ~]# setsebool -P httpd_can_network_connect on Killed [root@centos6 ~]# sestatus -b | grep httpd_can_network_connect httpd_can_network_connect off httpd_can_network_connect_cobbler off httpd_can_network_connect_db off I watched log file, but there was no log messages: tail -f /var/log/audit/audit.log UPDATE: There are some information in /var/log/messages: Nov 9 19:07:16 vs302 kernel: setsebool invoked oom-killer: gfp_mask=0x280da, order=0, oom_adj=0, oom_score_adj=0 Nov 9 19:07:16 vs302 kernel: setsebool cpuset=/ mems_allowed=0 Nov 9 19:07:16 vs302 kernel: Pid: 1660, comm: setsebool Not tainted 2.6.32-358.23.2.el6.x86_64 #1 Nov 9 19:07:16 vs302 kernel: Call Trace: Nov 9 19:07:16 vs302 kernel: [<ffffffff810cb641>] ? cpuset_print_task_mems_allowed+0x91/0xb0 Nov 9 19:07:16 vs302 kernel: [<ffffffff8111ce40>] ? dump_header+0x90/0x1b0 Nov 9 19:07:16 vs302 kernel: [<ffffffff8111d2c2>] ? oom_kill_process+0x82/0x2a0 Nov 9 19:07:16 vs302 kernel: [<ffffffff8111d201>] ? select_bad_process+0xe1/0x120 Nov 9 19:07:16 vs302 kernel: [<ffffffff8111d700>] ? out_of_memory+0x220/0x3c0 Nov 9 19:07:16 vs302 kernel: [<ffffffff8112c3dc>] ? __alloc_pages_nodemask+0x8ac/0x8d0 Nov 9 19:07:16 vs302 kernel: [<ffffffff81160d6a>] ? alloc_pages_vma+0x9a/0x150 Nov 9 19:07:16 vs302 kernel: [<ffffffff81143f0b>] ? handle_pte_fault+0x76b/0xb50 Nov 9 19:07:16 vs302 kernel: [<ffffffff81228664>] ? task_has_capability+0xb4/0x110 Nov 9 19:07:16 vs302 kernel: [<ffffffff81004a49>] ? __raw_callee_save_xen_pmd_val+0x11/0x1e Nov 9 19:07:16 vs302 kernel: [<ffffffff8114452a>] ? handle_mm_fault+0x23a/0x310 Nov 9 19:07:16 vs302 kernel: [<ffffffff811485b6>] ? vma_adjust+0x556/0x5e0 Nov 9 19:07:16 vs302 kernel: [<ffffffff810474e9>] ? __do_page_fault+0x139/0x480 Nov 9 19:07:16 vs302 kernel: [<ffffffff81148b8a>] ? vma_merge+0x29a/0x3e0 Nov 9 19:07:16 vs302 kernel: [<ffffffff81149fdc>] ? do_brk+0x26c/0x350 Nov 9 19:07:16 vs302 kernel: [<ffffffff8100ba1d>] ? retint_restore_args+0x5/0x6 Nov 9 19:07:16 vs302 kernel: [<ffffffff81513bfe>] ? do_page_fault+0x3e/0xa0 Nov 9 19:07:16 vs302 kernel: [<ffffffff81510fb5>] ? page_fault+0x25/0x30 Nov 9 19:07:16 vs302 kernel: Mem-Info: Nov 9 19:07:16 vs302 kernel: Node 0 DMA per-cpu: Nov 9 19:07:16 vs302 kernel: CPU 0: hi: 0, btch: 1 usd: 0 Nov 9 19:07:16 vs302 kernel: Node 0 DMA32 per-cpu: Nov 9 19:07:16 vs302 kernel: CPU 0: hi: 186, btch: 31 usd: 30 Nov 9 19:07:16 vs302 kernel: active_anon:132249 inactive_anon:46 isolated_anon:0 Nov 9 19:07:16 vs302 kernel: active_file:56 inactive_file:59 isolated_file:0 Nov 9 19:07:16 vs302 kernel: unevictable:0 dirty:2 writeback:0 unstable:0 Nov 9 19:07:16 vs302 kernel: free:1369 slab_reclaimable:1774 slab_unreclaimable:11588 Nov 9 19:07:16 vs302 kernel: mapped:54 shmem:48 pagetables:1211 bounce:0 Nov 9 19:07:16 vs302 kernel: Node 0 DMA free:2440kB min:72kB low:88kB high:108kB active_anon:12156kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:14648kB mlocked:0kB dirty:0kB writeback:0kB mapped:0kB shmem:0kB slab_reclaimable:24kB slab_unreclaimable:8kB kernel_stack:0kB pagetables:16kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? yes Nov 9 19:07:16 vs302 kernel: lowmem_reserve[]: 0 590 590 590 Nov 9 19:07:16 vs302 kernel: Node 0 DMA32 free:3036kB min:3072kB low:3840kB high:4608kB active_anon:516840kB inactive_anon:184kB active_file:224kB inactive_file:236kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:604988kB mlocked:0kB dirty:8kB writeback:0kB mapped:216kB shmem:192kB slab_reclaimable:7072kB slab_unreclaimable:46344kB kernel_stack:880kB pagetables:4828kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:128 all_unreclaimable? no Nov 9 19:07:16 vs302 kernel: lowmem_reserve[]: 0 0 0 0 Nov 9 19:07:16 vs302 kernel: Node 0 DMA: 0*4kB 1*8kB 0*16kB 0*32kB 0*64kB 1*128kB 1*256kB 0*512kB 0*1024kB 1*2048kB 0*4096kB = 2440kB Nov 9 19:07:16 vs302 kernel: Node 0 DMA32: 129*4kB 67*8kB 30*16kB 19*32kB 6*64kB 2*128kB 1*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 3036kB Nov 9 19:07:16 vs302 kernel: 182 total pagecache pages Nov 9 19:07:16 vs302 kernel: 0 pages in swap cache Nov 9 19:07:16 vs302 kernel: Swap cache stats: add 0, delete 0, find 0/0 Nov 9 19:07:16 vs302 kernel: Free swap = 0kB Nov 9 19:07:16 vs302 kernel: Total swap = 0kB Nov 9 19:07:16 vs302 kernel: 157439 pages RAM Nov 9 19:07:16 vs302 kernel: 6271 pages reserved Nov 9 19:07:16 vs302 kernel: 2686 pages shared Nov 9 19:07:16 vs302 kernel: 146395 pages non-shared Nov 9 19:07:16 vs302 kernel: [ pid ] uid tgid total_vm rss cpu oom_adj oom_score_adj name Nov 9 19:07:16 vs302 kernel: [ 271] 0 271 2798 231 0 -17 -1000 udevd Nov 9 19:07:16 vs302 kernel: [ 476] 0 476 2797 230 0 -17 -1000 udevd Nov 9 19:07:16 vs302 kernel: [ 718] 0 718 2279 122 0 0 0 dhclient Nov 9 19:07:16 vs302 kernel: [ 762] 0 762 6909 58 0 -17 -1000 auditd Nov 9 19:07:16 vs302 kernel: [ 787] 0 787 62270 147 0 0 0 rsyslogd Nov 9 19:07:16 vs302 kernel: [ 801] 25 801 40326 2655 0 0 0 named Nov 9 19:07:16 vs302 kernel: [ 850] 0 850 16563 172 0 -17 -1000 sshd Nov 9 19:07:16 vs302 kernel: [ 875] 0 875 23451 240 0 0 0 sshd Nov 9 19:07:16 vs302 kernel: [ 966] 498 966 4780 44 0 0 0 wrapper Nov 9 19:07:16 vs302 kernel: [ 968] 498 968 497404 40812 0 0 0 java Nov 9 19:07:16 vs302 kernel: [ 1057] 0 1057 20216 225 0 0 0 master Nov 9 19:07:16 vs302 kernel: [ 1064] 89 1064 20278 209 0 0 0 qmgr Nov 9 19:07:16 vs302 kernel: [ 1071] 0 1071 27075 121 0 0 0 bash Nov 9 19:07:16 vs302 kernel: [ 1111] 0 1111 24880 350 0 0 0 httpd Nov 9 19:07:16 vs302 kernel: [ 1117] 48 1117 24913 351 0 0 0 httpd Nov 9 19:07:16 vs302 kernel: [ 1118] 48 1118 24880 337 0 0 0 httpd Nov 9 19:07:16 vs302 kernel: [ 1119] 48 1119 24880 337 0 0 0 httpd Nov 9 19:07:16 vs302 kernel: [ 1120] 48 1120 24880 337 0 0 0 httpd Nov 9 19:07:16 vs302 kernel: [ 1121] 48 1121 24880 337 0 0 0 httpd Nov 9 19:07:16 vs302 kernel: [ 1122] 48 1122 24880 337 0 0 0 httpd Nov 9 19:07:16 vs302 kernel: [ 1124] 48 1124 24880 337 0 0 0 httpd Nov 9 19:07:16 vs302 kernel: [ 1125] 48 1125 24880 337 0 0 0 httpd Nov 9 19:07:16 vs302 kernel: [ 1129] 0 1129 29313 151 0 0 0 crond Nov 9 19:07:16 vs302 kernel: [ 1143] 0 1143 1018 22 0 0 0 agetty Nov 9 19:07:16 vs302 kernel: [ 1146] 0 1146 1015 22 0 0 0 mingetty Nov 9 19:07:16 vs302 kernel: [ 1514] 0 1514 23451 237 0 0 0 sshd Nov 9 19:07:16 vs302 kernel: [ 1517] 0 1517 27075 113 0 0 0 bash Nov 9 19:07:16 vs302 kernel: [ 1641] 89 1641 20236 218 0 0 0 pickup Nov 9 19:07:16 vs302 kernel: [ 1659] 0 1659 25234 39 0 0 0 tail Nov 9 19:07:16 vs302 kernel: [ 1660] 0 1660 89903 85712 0 0 0 setsebool Nov 9 19:07:16 vs302 kernel: Out of memory: Kill process 1660 (setsebool) score 568 or sacrifice child Nov 9 19:07:16 vs302 kernel: Killed process 1660, UID 0, (setsebool) total-vm:359612kB, anon-rss:342708kB, file-rss:140kB

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• Unobtrusive jQuery and Rails with AJAX and form validation

  - by bogumbiker

  Hello, I am looking for a way to call successfully custom function from submitHandler to do proper ajax post. Here is my custom function: jQuery.fn.submitWithAjax = function() { this.submit(function() { $.post(this.action, $(this).serialize(), null, "script"); return false; }) return this; }; Before using validate plugin I had following which worked fine: $(document).ready(function() { $("#my_form").submitWithAjax(); } Now I have added the validation part and have no idea how to call my custom submitWithAjax function?? $(document).ready(function() { $("#my_form").validate({ /*Validations - works perfectly!! */ }, submitHandler: function(form) { /* $("#my_form").submitWithAjax(); - this works but introduces recursion */ /* how to call custom subitWithAjax() ????? */ } }); }) Thanks!

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• Programmatically modifying an embedded resource before registering/referencing it on the page

  - by Jimock

  Hi All, Firstly, "Modifying" may be the wrong term, I see a few people have posted online just asking whether they can actually modify an embedded resource. What I am wanting to to, is use a resource in my assembly as a kind of template which I would do a find and replace on before registering it on the page - is this possible? For example; say I have a few lines of jQuery as an embedded resource in my assembly and in this script I am referencing a CSS class name that can be set by the front-end programmer. Since I do not know what the CSS class will be until implementation, is there a way of going through the embedded resource and replacing, say, $myclass$ with ThisClassName. Any help would be appreciated, if it's not possible then at least tell me so I can stop chasing my tail. Cheers, James

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• algorithm diagram

  - by tunl

  This is the max searching algorithm diagram: So, I wonder how can draw diagram for Recursion in HaNoi Tower program: package tunl; public class TowersApp { static int n = 3; public static void main(String[] args) { TowersApp.doTowers(3, 'A', 'B', 'C'); } public static void doTowers(int n, char from, char inter, char to) { if (n == 1) { System.out.println("disk 1 from "+ from + " to " + to); } else { doTowers(n-1, from, to, inter); System.out.println("disk " + n + " from " + from + " to " + to); doTowers(n-1, inter, from, to); } } } I can't draw it. Anyone can help me !!!

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• How are lists implemented in Haskell (GHC)?

  - by eman

  I was just curious about some exact implementation details of lists in Haskell (GHC-specific answers are fine)--are they naive linked lists, or do they have any special optimizations? More specifically: Do length and (!!) (for instance) have to iterate through the list? If so, are their values cached in any way (i.e., if I call length twice, will it have to iterate both times)? Does access to the back of the list involve iterating through the whole list? Are infinite lists and list comprehensions memoized? (i.e., for fib = 1:1:zipWith (+) fib (tail fib), will each value be computed recursively, or will it rely on the previous computed value?) Any other interesting implementation details would be much appreciated. Thanks in advance!

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