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  • tool to find out distance in terms of no. of hops in unix

    - by mawia
    Hi! all, I am writing an application for video streaming.In the application server is required to know the distance of the client from it self in terms of hop number.My question is,is there any tool/method other than traceroute available in unix environment to find it? I also need to find out the geographical location of the client.So is their any tool/method for this as well? Any help in this regard will be highly appreciated. Thanks in advance. Mawia

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  • SQlite: Column format for unix timestamp; Integer types

    - by SF.
    Original problem: What is the right column format for a unix timestamp? The net is full of confusion: some posts claim SQLite has no unsigned types - either whatsoever, or with exception of the 64bit int type (but there are (counter-)examples that invoke UNSIGNED INTEGER). The data types page mentions it only in a bigint example. It also claims there is a 6-byte integer but doesn't give a name for it. Of course standard INTEGER being 4-byte signed signed stores unix timestamps as negative numbers. I've heard that some systems return 64-bit timestamps too. OTOH I'm not too fond of wasting 4 bytes to store 1 extra bit (top bit of timestamp), and even if I have to pick a bigger data format, I'd rather go for the 6-byte one. I've even seen a post that claims SQLite unix timestamp is of type REAL... Complete problem: Could someone please clarify that mess?

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  • How to Practice Unix Programming in C?

    - by danben
    After five years of professional Java (and to a lesser extent, Python) programming and slowly feeling my CS education slip away, I decided I wanted to broaden my horizons / general usefulness to the world and do something that feels more (to me) like I really have an influence over the machine. I chose to learn C and Unix programming since I feel like that is where many of the most interesting problems are. My end goal is to be able to do this professionally, if for no other reason than the fact that I have to spend 40-50 hours per week on work that pays the bills, so it may as well also be the type of coding I want to get better at. Of course, you don't get hired to do things you haven't dont before, so for now I am ramping up on my own. To this end, I started with K&R, which was a great resource in part due to the exercises spread throughout each chapter. After that I moved on to Computer Systems: A Programmer's Perspective, followed by ten chapters of Advanced Programming in the Unix Environment. When I am done with this book, I will read Unix Network Programming. What I'm missing in the Stevens books is the lack of programming problems; they mainly document functionality and provide examples, with a few end-of-chapter questions following. I feel that I would benefit much more from being challenged to use the knowledge in each chapter ala K&R. I could write some test program for each function, but this is a less desirable method as (1) I would probably be less motivated than if I were rising to some external challenge, and (2) I will naturally only think to use the function in the ways that have already occurred to me. So, I'd like to get some recommendations on how to practice. Obviously, my first choice would be to find some resource that has Unix programming challenges. I have also considered finding and attempting to contribute to some open source C project, but this is a bit daunting as there would be some overhead in learning to use the software, then learning the codebase. The only open-source C project I can think of that I use regularly is Python, and I'm not sure how easy that would be to get started on. That said, I'm open to all kinds of suggestions as there are likely things I haven't even thought of.

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  • Better way to set unix permissions when deploying war file

    - by Chris G
    We have a vendor application where we download their updates and deploy a war file. We are deploying the war file on a unix application server running oracle application server 9i. I believe when we deploy the war file, we remove the previous install and then deploy the new war file. When we deploy the war file, sometimes we have to manually set the unix file permissions for the class and other files. We do this so all the unix user ids can run the processes they need. Is there a better way to do this?

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  • How to validate Windows VC++ DLL on Unix systems

    - by Guildencrantz
    I have a solution, mostly C#, but with a few VC++ projects, that is pushed through our standard release process (perl and bash scripts on Unix boxes). Currently the initiative is to validate DLL and EXE versions as they pass through the process. All the versioning is set so that File Version is of the format $Id: $ (between the colon and the second dollar should be a git commit hash), and the Product Version is of the format $Hudson Build: $ (between the colon and the second dollar should be a string representing the hudson build details). Currently this system works extremely well for the C# projects because this version information is stored as plain strings within the compiled code (you can literally use the unix strings command and see the version information); the problem is that the VC++ projects do not expose this information as strings (I have used a windows system to verify that the version information is correctly being set), so I'm not sure how to extract the version on a unix system. Any suggestions for either A) Getting a string representation of the version embedded in the compiled code, or B) A utility/script which can extract this information?

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  • Postfix Postscreen: how to use postscreen for smtp and smtps both

    - by petermolnar
    I'm trying to get postscreen work. I've followed the man page and it's already running correctly for smtp. But it I want to use it for smtps as well (adding the same line as smtp in master.cf but with smtps) i receive failure messages in syslog like: postfix/postscreen[8851]: fatal: btree:/var/lib/postfix/postscreen_cache: unable to get exclusive lock: Resource temporarily unavailable Some say that postscreen can only run once; that's ok. But can I use the same postscreen session for both smtp and smtps? If not, how to enable postscreen for smtps as well? Any help would be apprecieted! The parts of the configs: main.cf postscreen_access_list = permit_mynetworks, cidr:/etc/postfix/postscreen_access.cidr postscreen_dnsbl_threshold = 8 postscreen_dnsbl_sites = dnsbl.ahbl.org*3 dnsbl.njabl.org*3 dnsbl.sorbs.net*3 pbl.spamhaus.org*3 cbl.abuseat.org*3 bl.spamcannibal.org*3 nsbl.inps.de*3 spamrbl.imp.ch*3 postscreen_dnsbl_action = enforce postscreen_greet_action = enforce master.cf (full) smtpd pass - - n - - smtpd smtp inet n - n - 1 postscreen tlsproxy unix - - n - 0 tlsproxy dnsblog unix - - n - 0 dnsblog ### the problematic line ### smtps inet n - - - - smtpd pickup fifo n - - 60 1 pickup cleanup unix n - - - 0 cleanup qmgr fifo n - n 300 1 qmgr tlsmgr unix - - - 1000? 1 tlsmgr rewrite unix - - - - - trivial-rewrite bounce unix - - - - 0 bounce defer unix - - - - 0 bounce trace unix - - - - 0 bounce verify unix - - - - 1 verify flush unix n - - 1000? 0 flush proxymap unix - - n - - proxymap proxywrite unix - - n - 1 proxymap smtp unix - - - - - smtp relay unix - - - - - smtp showq unix n - - - - showq error unix - - - - - error retry unix - - - - - error discard unix - - - - - discard local unix - n n - - local virtual unix - n n - - virtual lmtp unix - - - - - lmtp anvil unix - - - - 1 anvil scache unix - - - - 1 scache dovecot unix - n n - - pipe flags=DRhu user=virtuser:virtuser argv=/usr/bin/spamc -e /usr/lib/dovecot/deliver -d ${recipient} -f {sender}

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  • Is copy paste programming bad ?

    - by ring bearer
    With plain google as well as google code search tools it is easy to find how to program using some resource or solve certain problems ( such as a Java class, or a ftp block in perl etc) and so developers are so tempted to just purely copy paste the code (in a way re-use) - is this an incompetency? I have done this myself though I think I am a better programmer than many others I have seen. Who has the time to RTFM? In this age of information abundance, I do not think that copy paste programming is bad. Isn't that what sites like stackoverflow do anyway? People ask - ok here is my problem - how to solve it? now someone will post complete code and the person who asked the question would simply copy paste the most voted answer. No matter how small the problem is. I am working with a bunch of young coders who heavily rely on internet to get their job done. I see convenience (for example, you may be quite good with algorithms and such but you may not know how to use a BufferedReader in Java - would you read complete Javadoc for BufferedReader or look up some example of using it somewhere??) in copy pasting and modifying code to get the job done. What are the real dangers of copy paste coding that can impact their competency?

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  • Functional programming and stateful algorithms

    - by bigstones
    I'm learning functional programming with Haskell. In the meantime I'm studying Automata theory and as the two seem to fit well together I'm writing a small library to play with automata. Here's the problem that made me ask the question. While studying a way to evaluate a state's reachability I got the idea that a simple recursive algorithm would be quite inefficient, because some paths might share some states and I might end up evaluating them more than once. For example, here, evaluating reachability of g from a, I'd have to exclude f both while checking the path through d and c: So my idea is that an algorithm working in parallel on many paths and updating a shared record of excluded states might be great, but that's too much for me. I've seen that in some simple recursion cases one can pass state as an argument, and that's what I have to do here, because I pass forward the list of states I've gone through to avoid loops. But is there a way to pass that list also backwards, like returning it in a tuple together with the boolean result of my canReach function? (although this feels a bit forced) Besides the validity of my example case, what other techniques are available to solve this kind of problems? I feel like these must be common enough that there have to be solutions like what happens with fold* or map. So far, reading learnyouahaskell.com I didn't find any, but consider I haven't touched monads yet. (if interested, I posted my code on codereview)

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  • Thread safe GUI programming

    - by James
    I have been programming Java with swing for a couple of years now, and always accepted that GUI interactions had to happen on the Event Dispatch Thread. I recently started to use GTK+ for C applications and was unsurprised to find that GUI interactions had to be called on gtk_main. Similarly, I looked at SWT to see in what ways it was different to Swing and to see if it was worth using, and again found the UI thread idea, and I am sure that these 3 are not the only toolkits to use this model. I was wondering if there is a reason for this design i.e. what is the reason for keeping UI modifications isolated to a single thread. I can see why some modifications may cause issues (like modifying a list while it is being drawn), but I do not see why these concerns pass on to the user of the API. Is there a limit imposed by an operating system? Is there a good reason these concerns are not 'hidden' (i.e. some form of synchronization that is invisible to the user)? Is there any (even purely conceptual) way of creating a thread safe graphics library, or is such a thing actually impossible? I found this http://blogs.operationaldynamics.com/andrew/software/gnome-desktop/gtk-thread-awareness which seems to describe GTK differently to how I understood it (although my understanding was the same as many people's) How does this differ to other toolkits? Is it possible to implement this in Swing (as the EDT model does not actually prevent access from other threads, it just often leads to Exceptions)

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  • C# Threading Background Process - Programming - How to?

    - by Magic
    Hello...I have been given the horrible task of doing this. Launch the website Take a screenshot Fill in the form details, click on Next Take a screenshot ... ... ... Rinse. Repeat. Now, with various combinations, this comes up to 300 screenshots. And I have to do this for 4 different browsers. Chrome, Firefox, IE 6 and IE 7. I cannot use tools which will capture the screenshot and store them, such as, SnagIT. I need to take a screenshot, copy it to a Word Document and take the second screenshot and take it to a Word Document. I thought, I will write a tiny utility which will help me do this. Here is the requirement spec that I put up for it - An executable which once launched seats itself in the System Tray. While it is active, all instances of Key Press (Print Scrn), it should write the contents to a Word Document as defined (either a default path or a user defined one). Save the document periodically. Now, my question is - if I am going to develop this using C# (Winforms application), how do I go about doing this. I can do a fair bit of C# programming and I am willing to learn. But I am not able to locate the references for how to do a background process so that it runs in the background. And while it runs, it has to capture the Print Scrn command. Can you folks point me to the right material where I can learn this? Theoretical references should suffice. But if there are practical references, then nothing like it. Thanks!

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  • Learning by doing (and programming by trial and error)

    - by AlexBottoni
    How do you learn a new platform/toolkit while producing working code and keeping your codebase clean? When I know what I can do with the underlying platform and toolkit, I usually do this: I create a new branch (with GIT, in my case) I write a few unit tests (with JUnit, for example) I write my code until it passes my tests So far, so good. The problem is that very often I do not know what I can do with the toolkit because it is brand new to me. I work as a consulant so I cannot have my preferred language/platform/toolkit. I have to cope with whatever the customer uses for the task at hand. Most often, I have to deal (often in a hurry) with a large toolkit that I know very little so I'm forced to "learn by doing" (actually, programming by "trial and error") and this makes me anxious. Please note that, at some point in the learning process, usually I already have: read one or more five-stars books followed one or more web tutorials (writing working code a line at a time) created a couple of small experimental projects with my IDE (IntelliJ IDEA, at the moment. I use Eclipse, Netbeans and others, as well.) Despite all my efforts, at this point usually I can just have a coarse understanding of the platform/toolkit I have to use. I cannot yet grasp each and every detail. This means that each and every new feature that involves some data preparation and some non-trivial algorithm is a pain to implement and requires a lot of trial-and-error. Unfortunately, working by trial-and-error is neither safe nor easy. Actually, this is the phase that makes me most anxious: experimenting with a new toolkit while producing working code and keeping my codebase clean. Usually, at this stage I cannot use the Eclipse Scrapbook because the code I have to write is already too large and complex for this small tool. In the same way, I cannot use any more an indipendent small project for my experiments because I need to try the new code in place. I can just write my code in place and rely on GIT for a safe bail-out. This makes me anxious because this kind of intertwined, half-ripe code can rapidly become incredibly hard to manage. How do you face this phase of the development process? How do you learn-by-doing without making a mess of your codebase? Any tips&tricks, best practice or something like that?

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  • How to get better at solving Dynamic programming problems

    - by newbie
    I recently came across this question: "You are given a boolean expression consisting of a string of the symbols 'true', 'false', 'and', 'or', and 'xor'. Count the number of ways to parenthesize the expression such that it will evaluate to true. For example, there is only 1 way to parenthesize 'true and false xor true' such that it evaluates to true." I knew it is a dynamic programming problem so i tried to come up with a solution on my own which is as follows. Suppose we have a expression as A.B.C.....D where '.' represents any of the operations and, or, xor and the capital letters represent true or false. Lets say the number of ways for this expression of size K to produce a true is N. when a new boolean value E is added to this expression there are 2 ways to parenthesize this new expression 1. ((A.B.C.....D).E) ie. with all possible parenthesizations of A.B.C.....D we add E at the end. 2. (A.B.C.(D.E)) ie. evaluate D.E first and then find the number of ways this expression of size K can produce true. suppose T[K] is the number of ways the expression with size K produces true then T[k]=val1+val2+val3 where val1,val2,val3 are calculated as follows. 1)when E is grouped with D. i)It does not change the value of D ii)it inverses the value of D in the first case val1=T[K]=N.( As this reduces to the initial A.B.C....D expression ). In the second case re-evaluate dp[K] with value of D reversed and that is val1. 2)when E is grouped with the whole expression. //val2 contains the number of 'true' E will produce with expressions which gave 'true' among all parenthesized instances of A.B.C.......D i) if true.E = true then val2 = N ii) if true.E = false then val2 = 0 //val3 contains the number of 'true' E will produce with expressions which gave 'false' among all parenthesized instances of A.B.C.......D iii) if false.E=true then val3=( 2^(K-2) - N ) = M ie. number of ways the expression with size K produces a false [ 2^(K-2) is the number of ways to parenthesize an expression of size K ]. iv) if false.E=false then val3 = 0 This is the basic idea i had in mind but when i checked for its solution http://people.csail.mit.edu/bdean/6.046/dp/dp_9.swf the approach there was completely different. Can someone tell me what am I doing wrong and how can i get better at solving DP so that I can come up with solutions like the one given above myself. Thanks in advance.

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  • HTML5 game programming style

    - by fnx
    I am currently trying learn javascript in form of HTML5 games. Stuff that I've done so far isn't too fancy since I'm still a beginner. My biggest concern so far has been that I don't really know what is the best way to code since I don't know the pros and cons of different methods, nor I've found any good explanations about them. So far I've been using the worst (and propably easiest) method of all (I think) since I'm just starting out, for example like this: var canvas = document.getElementById("canvas"); var ctx = canvas.getContext("2d"); var width = 640; var height = 480; var player = new Player("pic.png", 100, 100, ...); also some other global vars... function Player(imgSrc, x, y, ...) { this.sprite = new Image(); this.sprite.src = imgSrc; this.x = x; this.y = y; ... } Player.prototype.update = function() { // blah blah... } Player.prototype.draw = function() { // yada yada... } function GameLoop() { player.update(); player.draw(); setTimeout(GameLoop, 1000/60); } However, I've seen a few examples on the internet that look interesting, but I don't know how to properly code in these styles, nor do I know if there are names for them. These might not be the best examples but hopefully you'll get the point: 1: Game = { variables: { width: 640, height: 480, stuff: value }, init: function(args) { // some stuff here }, update: function(args) { // some stuff here }, draw: function(args) { // some stuff here }, }; // from http://codeincomplete.com/posts/2011/5/14/javascript_pong/ 2: function Game() { this.Initialize = function () { } this.LoadContent = function () { this.GameLoop = setInterval(this.RunGameLoop, this.DrawInterval); } this.RunGameLoop = function (game) { this.Update(); this.Draw(); } this.Update = function () { // update } this.Draw = function () { // draw game frame } } // from http://www.felinesoft.com/blog/index.php/2010/09/accelerated-game-programming-with-html5-and-canvas/ 3: var engine = {}; engine.canvas = document.getElementById('canvas'); engine.ctx = engine.canvas.getContext('2d'); engine.map = {}; engine.map.draw = function() { // draw map } engine.player = {}; engine.player.draw = function() { // draw player } // from http://that-guy.net/articles/ So I guess my questions are: Which is most CPU efficient, is there any difference between these styles at runtime? Which one allows for easy expandability? Which one is the most safe, or at least harder to hack? Are there any good websites where stuff like this is explained? or... Does it all come to just personal preferance? :)

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  • Unix/Linux find and sort by date modified

    - by Richard Easton
    How can I do a simple find which would order the results by most recently modified? Here is the current find I am using (I am doing a shell escape in PHP, so that is the reasoning for the variables): find '$dir' -name '$str'\* -print | head -10 How could I have this order the search by most recently modified? (Note I do not want it to sort 'after' the search, but rather find the results based on what was most recently modified.)

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  • Unix : `nc` on Ubuntu vs Redhat (netcat)

    - by bguiz
    How do I achieve the equivalent of nc -q in Redhat 5? Details? nc -q -1 local host ${PORT} ${CMD} In Ubuntu, nc may be use as above, with the -q option. See manpage. -q after EOF on stdin, wait the specified number of seconds and then quit. If seconds is negative, wait forever. However, this option is not available in Redhat 5. See manpage. (Note: The Red Hat website is horrible to search, if someone finds their manpage for nc, please edit this post or comment with the new link).

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  • Unix LVM: how to resize root lvm

    - by Hussein Sabbagh
    I took over a virtual server at work after a co-worker left. He, however, setup the server incorrectly at multiple stages and im cleaning them up as I run into them... Currently I realized that the file system is broken in half onto 2 logical volumes both at 50gb. One is mounted as the root directory and the other as the /home directory. Saddly, the server has taken up 46gb of the root lv and i need to expand it. I have already shrunk and remounted the home lv. I resized the root lv, but I can't figure out how to unmount the root directory while the computer is on. Obviously this needs to be done before I can finalize the expansion, but I don't know how. I'd appreciate any help or pointing in the right direction. Thanks in advance. PS this is on a CentOS server.

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  • Unix list absolute file name

    - by Matthew Adams
    Given an arbitrary single argument representing a file (or directory, device, etc), how do I get the absolute path of the argument? I've seen many answers to this question involving find/ls/stat/readlink and $PWD, but none that suits my need. It looks like the closest answer is ksh's "whence" command, but I need it to work in sh/bash. Assume a file, foo.txt, is located in my home directory, /Users/matthew/foo.txt. I need the following behavior, despite what my current working directory is (I'm calling the command "abs"): (PWD is ~) $ abs foo.txt /Users/matthew/foo.txt $ abs ~/foo.txt /Users/matthew/foo.txt $ abs ./foo.txt /Users/matthew/foo.txt $ abs /Users/matthew/foo.txt /Users/matthew/foo.txt What would "abs" really be? TIA, Matthew

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  • Setting default path in Unix

    - by eSKay
    I just installed valgrind on my Fedora12 machine. $ valgrind // 1 $ valgrind: Command not found. //error $ /usr/local/bin/valgrind // 2 works fine My $PATH has /usr/local/bin in it. Is there something else that I need to do to make 1 work?

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  • Recursive move utility on Unix?

    - by Thomas Vander Stichele
    Sometimes I have two trees that used to have the same content, but have grown out of sync (because I moved disks around or whatever). A good example is a tree where I mirror upstream packages from Fedora. I want to merge those two trees again by moving all of the files from tree1 into tree2. Usually I do this with: rsync -arv tree1/* tree2 Then delete tree1. However, this takes an awful lot of time and disk space, and it would be much easier to be able to do: mv -r tree1/* tree2 In other words, a recursive move. It would be faster because first of all it would not even copy, just move the inodes, and second I wouldn't need a delete at the end. Does this exist ? As a test case, consider the following sequence of commands: $ mkdir -p a/b $ touch a/b/c1 $ rsync -arv a/ a2 sending incremental file list created directory ./ b/ b/c1 b/c2 sent 173 bytes received 57 bytes 460.00 bytes/sec total size is 0 speedup is 0.00 $ touch a/b/c2 What command would now have the effect of moving a/b/c2 to a2/b/c2 and then deleting the a subtree (since everything in it is already in the destination tree) ?

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  • Combine multiple unix commands into one output

    - by Ben McCormack
    I need to search our mail logs for a specific e-mail address. We keep a current file named maillog as well as a week's worth of .bz2 files in the same folder. Currently, I'm running the following commands to search for the file: grep [email protected] maillog bzgrep [email protected] *.bz2 Is there a way combine the grep and bzgrep commands into a single output? That way, I could pipe the combined results to a single e-mail or a single file.

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  • Unix commandline to repeat command with pipes

    - by bguiz
    I want to write a script that will repeat a commandline that usually contains pipes ./myscript.sh ls -lart |grep ^d And in myscript.sh I do a bunch of stuff, and then want to execute ls -lart |grep ^d and pipe the output from that into something else. (sorry in advance if this is really simple and has a 1-liner solution). So far I have tried $@ | someothercommand and $* | someothercommand But to no avail...

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  • Perl under unix/linux

    - by folone
    Could anyone help me fix the following script: cat "test... test... test..." | perl -e '$??s:;s:s;;$?::s;;=]=>%-{<-|}<&|`{;;y; -/:-@[-`{-};`-{/" -;;s;;$_;see' It won't print to the output.

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  • UNIX User Account to Restricted SysAdmin (User/Printer Admin only)

    - by Mark
    Hi all, I'd like to know if there is a way for a user account to be enabled or elevated to carry out system admin tasks WITHOUT having to use the root account or sudo. Goal here is to allow a user account to Add/Delete users/printers without giving them the 'God' powers that the root account carries, in a way setting up a restricted system admin essentially. Not sure if there is a way of doing this as most just use root to my understanding.

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