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  • Script Bash and History Unix

    - by user1107078
    i just start to use Script bash on UNIX and i didnt find a solution to write the first command in the history which start , for example , with ls. If i write in the shell history !ls it works but when i'm going to create a script it wont work. This is my example code #!/bin/bash set -o | grep history set -o history #echo "HISTFILE is $HISTFILE" #history "!ls"; #history #!ls history #it works Another Question why echo "HISTFILE is $HISTFILE" print me only HISTFILE is ?? Thanks

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  • unix cut, remove first token

    - by Mike
    I'm trying to use unix cut to remove the first two fields per line. I have input lines of of the form (token)(whitespace)(token)(lots of text) The problem is that there exit n tokens per line, so I can't do something like this cut -f3,4,5,6,7,8,9 is there a way to tell cut to take everything except the specified fields

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  • file content into unix variable with newlines

    - by Hugo
    I have a text file test.txt with the following content: text1 text2 And I want to assign the content of the file to a UNIX variable but when I do this: testvar=$(cat test.txt) echo $testvar the reult is: text1 text2 instead of text1 text2 Can someone suggest me a solution for this?

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  • output redirection in UNIX

    - by Happy Mittal
    I am a beginner in UNIX. I am finding some difficulty in input/output redirection. ls -l temp cat temp Here why temp file is shown in the list and moreover, it is showing 0 characters. wc temp temp cat temp here output is 0 0 0 temp. Why lines, words, characters are 0. Please help me to undestand this concept.

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  • System.IO.Path or equivelent use with Unix paths

    - by pm_2
    Is it possible to either use the System.IO.Path class, or some similar object to format a unix style path, providing similar functionality to the PATH class? For example, I can do: Console.WriteLine(Path.Combine("c:\\", "windows")); Which shows: "C:\\windows" But is I try a similar thing with forward slashes (/) it just reverses them for me. Console.WriteLine(Path.Combine("/server", "mydir")); Which shows: "/server\\mydir"

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  • Self Modifying Code

    - by Betamoo
    I am recently thinking about writing self-modifying programs, I think it may be powerful and fun... So I am currently looking for a language that allow modifying program own code easily.. I read about C# and the ability to compile -and execute- code in runtime, but that is too hurting.. I am also thinking about assembly... it is easier there to change running code but it is not very powerful... Can you suggest me a powerful language -or a feature- that support modifying code in runtime..? Hint: That what I mean by modifying code in runtime Start: a=10,b=20,c=0 label1: c=a+b .... label1= c=a*b goto label1 Thanks

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  • Differentiate procedural language(c) from oop languages(c++)

    - by niko
    I have been trying to differentiate c and c++(or oop languages) but I don't understand where the difference is. Note I have never used c++ but I asked my friends and some of them to differentiate c and c++ They say c++ has oop concepts and also the public, private modes for definition of variables and which c does not have though. Seriously I have done vb.net programming for a while 2 to 3 months, I never faced a situation to use class concepts and modes of definition like public and private. So I thought what could be the use for these? My friend explained me a program saying that if a variable is public, it can be accessed anywhere I said why not declare it as a global variable like in c? He did not get back to my question and he said if a variable is private it cannot be accessed by some other functions I said why not define it as a local variable, even these he was unable to answer. No matter where I read private variables cannot be accessed whereas public variables can be then why not make public as global and private as local whats the difference? whats the real use of public and private ? please don't say it can be used by everyone, I suppose why not we use some conditions and make the calls? I have heard people saying security reasons, a friend said if a function need to be accessed it should be inherited first. He explained saying that only admin should be able to have some rights and not all so that functions are made private and inherited only by the admin to use Then I said why not we use if condition if ( login == "admin") invoke the function he still did not answer these question. Please clear me with these things, I have done vb.net and vba and little c++ without using oop concepts because I never found their real use while I was writing the code, I'm a little afraid am I too back in oop concepts?

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  • Functional Languages that compile to Android's Dalvik VM?

    - by Berin Loritsch
    I have a software problem that fits the functional approach to programming, but the target market will be on the Android OS. I ask because there are functional languages that compile to Java's VM, but Dalvik bytecode != Java bytecode. Alternatively, do you know if the dx utility can intelligently convert the .class files generated from functional languages like Scala? Edit: In order to add a bit more helpfulness to the community, and also to help me choose better, can I refine the question a bit? Have you used any alternate languages with Dalvik? Which ones? What are some "gotchas" (problems) that I might run into? Is performance acceptable? By that, I mean the application still feels responsive to the user. I've never done mobile phone development, but I grew up on constrained devices and I'm under no illusion that there is a cost to using non-standard languages with the platform. I just need to know if the cost is such that I should shoe-horn my approach into default language (i.e. apply functional principles in the OOP language).

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  • How often is your "Go-To" language the same as your favorite??

    - by K-RAN
    I know that there's already a question asking for your favorite programming language here. I'm curious though, what's your go-to language? The two can be very different. For example, I love Haskell. I learned it this past semester and I fell in love with it's very concise solutions and awesome syntax (I love theoretical math so something like fib = 1 : 1 : [ f | f <- zipWith (+) fibSeq (tail fibSeq)] makes my inner mathematician and computer scientist jump with joy!). However, the majority of my projects for classes and jobs have been in C/C++ & Java. As a result, most of the time when I'm testing something like an algorithm or Data Structure I go straight to C++. What about you guys? What languages do you love and why? What about your go-to language? What language do you use most often to get things done for work or personal projects and why? How often does a language fall into both categories??

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  • Is an event loop just a for/while loop with optimized polling?

    - by Alan
    I'm trying to understand what an event loop is. Often the explanation is that in the event loop, you do something until you're notified that an event occurred. You than handle the event and continue doing what you did before. To map the above definition with an example. I have a server which 'listens' in a event loop, and when a socket connection is detected, the data from it gets read and displayed, after which the server goes to the listening it did before. However, this event happening and us getting notified 'just like that' are to much for me to handle. You can say: "It's not 'just like that' you have to register an event listener". But what's an event listener but a function which for some reason isn't returning. Is it in it's own loop, waiting to be notified when an event happens? Should the event listener also register an event listener? Where does it end? Events are a nice abstraction to work with, however just an abstraction. I believe that in the end, polling is unavoidable. Perhaps we are not doing it in our code, but the lower levels (the programming language implementation or the OS) are doing it for us. It basically comes down to the following pseudo code which is running somewhere low enough so it doesn't result in busy waiting: while(True): do stuff check if event has happened (poll) do other stuff This is my understanding of the whole idea, and i would like to hear if this is correct. I am open in accepting that the whole idea is fundamentally wrong, in which case I would like the correct explanation. Best regards

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  • Advice: USB Monitoring Programming

    - by Kashif
    I need an advice about USB programming in linux. i have to design a USB monitoring program that 'll keep checking usb ports of a linux cent os. as soon as a usb or external hard disk is connected, this program will shoot an email to some specific person about detail of usb (as size, mount on, time). when usb is disconnected, it will again shoot an email to some person with same kind of information. mean while this program will also write logs in syslog/messages with name of programing for easy tracking. Now I want ask that what is best way to develop this program. as I'm new to this field so i know nothing about it? either i should use perl, bash scripting or some other language? I have no idea what is right way to adopt coz this program will keep running all the time to keep a check on usb ports. I know few commands in like lsusb, fdisk (to check attached usb) and df -h (to get detail of usb) but dont know how i can achieve using these commands that i am thinking. also one more thing that in future i also need to modify this program for ubuntu and Citrix XenServer and it should be same everywhere.

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  • UNIX Shell-scripting: UDV

    - by Myx
    I am writing a simple unix shell script: #!/bin/bash # abort the script if a command fails set -e # abort the script if an unitialized shell variable is used set -u i = 0; while [$i -l 1] do src/meshpro input/martini.off video/noise/image$i.off -noise $i src/meshview video/noise/image$i.off -output_image video/noise/image$i.jpg -exit_immediately i='expr $i + 0.1' done When I try to run the script, I get the following error: line 14: i: command not found. I used a tutorial to apply to my code. Any suggestions on what I'm doing wrong?

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  • C++ Multithreading on Unix

    - by Roger
    I have two related questions: 1) Are there any good books for multithreading in C++, especially now that C++11 contains multithreading in the standard library? 2) I have the Wrox Programming on Unix book (1000 pages fat red one) and within it, it uses the Unix Thread class. How does this code relate to boost and the C++11 multithreading libraries? Is it better/worse/just specific to Unix etc? Is the performance the same?

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  • Unix [Homework]: Get a list of /home/user/ directories in /etc/passwd

    - by KChaloux
    I'm very new to Unix, and currently taking a class learning the basics of the system and its commands. I'm looking for a single command line to list off all of the user home directories in alphabetical order from the /etc/passwd directory. This applies only to the home directories, and not the contents within them. There should be no duplicate entries. I've tried many permutations of commands such as the following: sort -d | find /etc/passwd /home/* -type -d | uniq | less I've tried using -path, -name, removing -type, using -prune, and changing the search pattern to things like /home/*/$, but haven't gotten good results once. At best I can get a list of my own directory (complete with every directory inside it, which is bad), and the directories of the other students on the server (without the contained directories, which is good). I just can't get it to display the /home/user directories and nothing else for my own account. Many thanks in advance.

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  • Unix shell script with Iseries command

    - by user293058
    I am trying to ftp a file from unix to as400 and executing iseries command in the script. ftp is working fine,I am getting an error in jobd command as HOST=KCBNSXDD.svr.us.bank.net USER=test PASS=1234 #This is the password for the FTP user. ftp -env $HOST << EOF # Call 2. Here the login credentials are supplied by calling the variables. user $USER $PASS # Call 3. Here you will change to the directory where you want to put or get cd "\$QARCVBEN" # Call4. Here you will tell FTP to put or get the file. #Ebcdic #Mode b quote site crtccsid *user quote site crtccsid *sysval put prod.txt quote rcmd sbmjob cmd(call pgm(pmtiprcc0) parm('prod' 'DEV')) job(\$pmtiprcc) jobd(orderbatch) 550-Error occurred on command SBMJOB cmd(call pgm(pmtiprcc0)) job($pmtiprcc) jobd(orderbatch). 550 Errors occurred on SBMJOB command.. 221 QUIT subcommand received.

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  • Novell est bien le propriétaire d'UNIX, SCO perd son procès

    Mise à jour du 31.03.2010 par Katleen Novell est bien le propriétaire d'UNIX, SCO perd son procès Un verdict très attendu dans le monde de l'informatique vient de tomber, après plusieurs années de procès. Du côté de l'open source, on retenait son souffle : la décision a être annoncée pouvait tout changer. Et c'est finalement le soulagement général : UNIX n'appartient pas à SCO. Le tribunal de Salt Lake City, dans l'Utah, vient de reconnaitre officiellement Novell comme propriétaire légitime d'UNIX. Les développeurs et éditeurs de distributions UNIX et Linux sont donc rassurés : tout est bien qui finit bien. Linux menacé de mort par...

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  • What's the best way to check that environment variables are set in Unix shellscript

    - by AndrewR
    I've got a few Unix shell scripts where I need to check that certain environment variables are set before I start doing stuff, so I do this sort of thing: if [ -z "$STATE" ]; then echo "Need to set STATE" exit 1 fi if [ -z "$DEST" ]; then echo "Need to set DEST" exit 1 fi which is a lot of typing. Is there a more elegant idiom for checking that a set of environment variables is set? EDIT: I should mention that these variables have no meaningful default value - the script should error out if any are unset.

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  • Reading / Writing from a Unix Socket in Ruby

    - by Olly
    I'm trying to connect, read and write from a UNIX socket in Ruby. It is a stats socket used by haproxy. My code is the following: require 'socket' socket = UNIXSocket.new("/tmp/haproxy.stats.socket") # First attempt: works socket.puts("show stat") while(line = socket.gets) do puts line end # Second attemp: fails socket.puts("show stat") while(line = socket.gets) do puts line end It succeeds the first time, but on the second attempt fails. I'm not sure why. # pxname,svname,qcur,qmax,scur,smax,slim,stot,bin,bout,dreq,dresp,ereq,econ,eresp,wretr,wredis,status,weight,act,bck,chkfail,chkdown,lastchg,downtime,qlimit,pid,iid,sid,throttle,lbtot,tracked,type,rate,rate_lim,rate_max,check_status,check_code,check_duration,hrsp_1xx,hrsp_2xx,hrsp_3xx,hrsp_4xx,hrsp_5xx,hrsp_other,hanafail,req_rate,req_rate_max,req_tot,cli_abrt,srv_abrt, stats,FRONTEND,,,0,0,2000,0,0,0,0,0,0,,,,,OPEN,,,,,,,,,1,1,0,,,,0,0,0,0,,,,0,0,0,0,0,0,,0,0,0,,, stats,BACKEND,0,0,0,0,2000,0,0,0,0,0,,0,0,0,0,UP,0,0,0,,0,22,0,,1,1,0,,0,,1,0,,0,,,,0,0,0,0,0,0,,,,,0,0, legacy_socket,FRONTEND,,,0,0,1000,0,0,0,0,0,0,,,,,OPEN,,,,,,,,,1,2,0,,,,0,0,0,0,,,,0,0,0,0,0,0,,0,0,0,,, all,FRONTEND,,,0,0,10000,0,0,0,0,0,0,,,,,OPEN,,,,,,,,,1,3,0,,,,0,0,0,0,,,,0,0,0,0,0,0,,0,0,0,,, socket_backend,socket,0,0,0,0,200,0,0,0,,0,,0,0,0,0,DOWN,1,1,0,0,1,22,22,,1,4,1,,0,,2,0,,0,L4CON,,0,0,0,0,0,0,0,0,,,,0,0, socket_backend,socket,0,0,0,0,200,0,0,0,,0,,0,0,0,0,DOWN,1,1,0,0,1,22,22,,1,4,2,,0,,2,0,,0,L4CON,,0,0,0,0,0,0,0,0,,,,0,0, socket_backend,socket,0,0,0,0,200,0,0,0,,0,,0,0,0,0,DOWN,1,1,0,0,1,22,22,,1,4,3,,0,,2,0,,0,L4CON,,0,0,0,0,0,0,0,0,,,,0,0, socket_backend,socket,0,0,0,0,200,0,0,0,,0,,0,0,0,0,DOWN,1,1,0,0,1,22,22,,1,4,4,,0,,2,0,,0,L4CON,,0,0,0,0,0,0,0,0,,,,0,0, socket_backend,socket,0,0,0,0,200,0,0,0,,0,,0,0,0,0,DOWN,1,1,0,0,1,22,22,,1,4,5,,0,,2,0,,0,L4CON,,0,0,0,0,0,0,0,0,,,,0,0, socket_backend,socket,0,0,0,0,200,0,0,0,,0,,0,0,0,0,DOWN,1,1,0,0,1,22,22,,1,4,6,,0,,2,0,,0,L4CON,,0,0,0,0,0,0,0,0,,,,0,0, socket_backend,socket,0,0,0,0,200,0,0,0,,0,,0,0,0,0,DOWN,1,1,0,0,1,22,22,,1,4,7,,0,,2,0,,0,L4CON,,0,0,0,0,0,0,0,0,,,,0,0, socket_backend,socket,0,0,0,0,200,0,0,0,,0,,0,0,0,0,DOWN,1,1,0,0,1,21,21,,1,4,8,,0,,2,0,,0,L4CON,,0,0,0,0,0,0,0,0,,,,0,0, socket_backend,socket,0,0,0,0,200,0,0,0,,0,,0,0,0,0,DOWN,1,1,0,0,1,21,21,,1,4,9,,0,,2,0,,0,L4CON,,0,0,0,0,0,0,0,0,,,,0,0, socket_backend,socket,0,0,0,0,200,0,0,0,,0,,0,0,0,0,DOWN,1,1,0,0,1,21,21,,1,4,10,,0,,2,0,,0,L4CON,,0,0,0,0,0,0,0,0,,,,0,0, socket_backend,BACKEND,0,0,0,0,0,0,0,0,0,0,,0,0,0,0,DOWN,0,0,0,,1,21,21,,1,4,0,,0,,1,0,,0,,,,0,0,0,0,0,0,,,,,0,0, api_backend,api,0,0,0,0,200,0,0,0,,0,,0,0,0,0,UP,1,1,0,0,0,22,0,,1,5,1,,0,,2,0,,0,L4OK,,0,0,0,0,0,0,0,0,,,,0,0, api_backend,api,0,0,0,0,1,0,0,0,,0,,0,0,0,0,UP,1,1,0,0,0,22,0,,1,5,2,,0,,2,0,,0,L4OK,,0,0,0,0,0,0,0,0,,,,0,0, api_backend,api,0,0,0,0,1,0,0,0,,0,,0,0,0,0,DOWN,1,1,0,0,1,21,21,,1,5,3,,0,,2,0,,0,L4CON,,0,0,0,0,0,0,0,0,,,,0,0, api_backend,BACKEND,0,0,0,0,0,0,0,0,0,0,,0,0,0,0,UP,2,2,0,,0,22,0,,1,5,0,,0,,1,0,,0,,,,0,0,0,0,0,0,,,,,0,0, www_backend,ruby-www,0,0,0,0,10000,0,0,0,,0,,0,0,0,0,UP,1,1,0,0,0,22,0,,1,6,1,,0,,2,0,,0,L4OK,,0,0,0,0,0,0,0,0,,,,0,0, www_backend,BACKEND,0,0,0,0,0,0,0,0,0,0,,0,0,0,0,UP,1,1,0,,0,22,0,,1,6,0,,0,,1,0,,0,,,,0,0,0,0,0,0,,,,,0,0, /Users/Olly/Desktop/haproxy_stats.rb:14:in `write': Broken pipe (Errno::EPIPE) from /Users/Olly/Desktop/haproxy_stats.rb:14:in `puts' from /Users/Olly/Desktop/haproxy_stats.rb:14 What is the problem? Is there a good reference to using UNIX sockets and Ruby?

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  • How to improve Algorithmic Programming Solving skill? [closed]

    - by gaurav
    Possible Duplicate: How can I improve my problem-solving ability? How do you improve your problem solving skills? Should I learn design patterns or algorithms to improve my logical thinking skills? What to do when you're faced with a problem that you can't solve quickly? Are there non-programming related activities akin to solving programming problems? I am a computer engineering graduate. I have studied programming since three years. I am good in coding and programming. I have been trying to compete in algorithmic competitions on sites such as topcoder,spoj since one and a half year, but I am still unable to solve problems other than too easy problems. I have learned from people that it takes practice to solve such problems. I try to solve those problems but sometimes I am unable to understand and even if I do understand I am unable to think of a good algorithm for solving it. Even if I solve I get Wrong answer and I am unable to figure out what is the problem with my code as it works on samples given on the sites but fails on test cases which they do not provide. I really want to solve those problems and become good in algorithms. I have read books for learning algorithms like Introduction to algorithms by CLRS,practicing programming questions. I have gone through some questions but they don't answer this question. I have seen the questions which are said duplicates but those questions focus on overall programming, but I am asking for algorithm related programming, basically for competing in programming which involve solving a problem statement then online judge will automatically evaluate it, such type of programming is quite different from the type of programming these questions discuss.

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  • How to format a dos path to a unix path on cygwin command line

    - by Jennette
    When using Cygwin, I frequently copy a Windows path and manually edit all of the slashes to Unix format. For example, if I am using Cygwin and need to change directory I enter: cd C:\windows\path then edit this to cd C:/windows/path (Typically, the path is much longer than that). Is there a way to use sed, or something else to do this automatically? For example, I tried: echo C:\windows\path|sed 's|\|g' but got the following error sed: -e expression #1, char 7: unterminated `s' command My goal is to reduce the typing, so maybe I could write a program which I could call. Ideally I would type: conversionScript cd C:/windows/path and this would be equivalent to typing: cd C:\windows\path

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  • Using Unix Process Controll Methods in Ruby

    - by John F. Miller
    Ryan Tomayko touched off quite a fire storm with this post about using Unix process control commands. We should be doing more of this. A lot more of this. I'm talking about fork(2), execve(2), pipe(2), socketpair(2), select(2), kill(2), sigaction(2), and so on and so forth. These are our friends. They want so badly just to help us. I have a bit of code (a delayed_job clone for DataMapper that I think would fit right in with this, but I'm not clear on how to take advantage of the listed commands. Any Ideas on how to improve this code? def start say "*** Starting job worker #{@name}" t = Thread.new do loop do delay = Update.work_off(self) break if $exit sleep delay break if $exit end clear_locks end trap('TERM') { terminate_with t } trap('INT') { terminate_with t } trap('USR1') do say "Wakeup Signal Caught" t.run end end

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