A script is a sequence of commands or instructions that are executed by an interpreter program rather than compiled into a standalone executable program.

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Allow setuid on shell scripts

The setuid permission bit tells Linux to run a program with the effective user id of the owner instead of the executor: > cat setuid-test.c #include <stdio.h> #include <unistd.h> int ...
33
votes
7answers
35k views

Looping through files with spaces in the names?

I wrote the following script to diff the outputs of two directores with all the same files in them as such: #!/bin/bash for file in `find . -name "*.csv"` do echo "file = $file"; diff ...
5
votes
3answers
4k views

Storing output of command in shell variable

I have an operation using cut that I would like to assign result to a variable var4=echo ztemp.xml |cut -f1 -d '.' I get the error: ztemp.xml is not a command The value of var4 never gets ...
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5answers
4k views

What Unix commands can be used as a semaphore/lock?

I want to run multiple Bash shell scripts in parallel. However, I want to avoid race conditions. What Unix commands are truly atomic that I could use for this purpose, and how can I use them?
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votes
8answers
3k views

Automatically run commands over SSH on many servers

There is a list of IP addresses in a .txt file, ex.: 1.1.1.1 2.2.2.2 3.3.3.3 Behind every IP address there is a server, and on every server there is an sshd running on port 22. Not every server is ...
138
votes
22answers
66k views

Repeat a Unix command every x seconds forever

There's a builtin Unix command repeat whose first argument is the number of times to repeat a command, where the command (with any arguments) is specified by the remaining arguments to repeat. For ...
4
votes
4answers
420 views

Check for Process if Same is Running

Is there a script or a way in linux that when I try to execute a shell script/process, if the same is running, it will prompt that same is running and will exit otherwise it will continue.
0
votes
1answer
837 views

/bin/sh: ./check-dependencies.pl: not found — but check-dependencies.pl exists!

I'm trying to build Moses, but when I run make I get the following output: minakshi@minakshi-Vostro-3500:~/Desktop/working-dir/moses/scripts$ make release # Compile the parts make all make[1]: ...
17
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8answers
5k views

Object-oriented shell for *nix

Preface: I love bash and have no intention of starting any sort of argument or holy-war, and hopefully this is not an extremely naive question. This question is somewhat related to this post on ...
12
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7answers
23k views

Execute remote commands, completely detaching from the ssh connection

I have 2 computers, localpc and remoteserver. I need localpc to execute some commands on remoteserver. One of the things it needs to do is start a backup script that runs for a number of hours. I ...
25
votes
2answers
5k views

What does “3>&1 1>&2 2>&3” do in a script?

I saw this line in a script: DEVICE=`dialog --inputbox "Festplatten-Laufzeit auslesen. Gebe Sie das gewünschte Device an: " 0 70 "" 3>&1 1>&2 2>&3` What is 3>&1 ...
6
votes
3answers
3k views

What is IFS in context of for looping?

I'm learning bash scripting right now. I was reading this thread: How to loop over the lines of a file? What is IFS? With for and IFS:
8
votes
5answers
920 views

How can I have more than one possibility in a script's shebang line?

I'm in a bit of an interesting situation where I have a Python script that can theoretically be run by a variety of users with a variety of environments (and PATHs) and on a variety of Linux systems. ...
6
votes
5answers
609 views

Shell programming, avoiding tempfiles

I often write KSH shell scripts that follow the same pattern: (1) retrieve output from one or more command (2) format it using grep|cut|awk|sed and print it to the screen or to a file In order to ...
2
votes
2answers
187 views

Commands for determining level of usage of server

I am scripting a new program that will connect to a cluster of machines in a VM park, and hopefully check their level of usage. The VM clients are a combination of RHEL and CentOS, and runs on ...
6
votes
1answer
175 views

Parallel execution of bash script

I have a table URL_Experiment in my database (mySQL database). I have 2 million URL links in this table. For each URL, I am checking if some particular text is present in the URL and updating the ...
20
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1answer
701 views

How to implement a horizontal cat? [duplicate]

Standard cat concatenates files line by line (row by row, if you will). I find myself needing a horizontal cat command more and more often recently; i.e. a command that takes a list of files and ...
5
votes
2answers
689 views

How to do a text replacement in a big folder hierarchy?

I want to search and replace some text in a large set of files excluding some instances. For each line, I want a prompt asking me if I need to replace that line or not. Something similar to vim's ...
9
votes
3answers
595 views

How to pipe the list of commands displayed by of “tab complete”?

When using commands in bash I like the double tab option to display the available commands. Some commands have more possible matches than others: Is there a way I can pipe the output of the double ...
16
votes
3answers
1k views

Does the shebang determine the shell which runs the script?

This may be a silly question, but I ask it still. If I have declared a shebang #!/bin/bash in the beginning of my_shell_script.sh, so do I always have to invoke this script using bash ...
4
votes
3answers
865 views

Keep running a script via ssh

ssh can use to run remote commands. ssh me@server.com 'long-script.sh' I run a long script that will take a lot of time, but I want to close my computer and keep running the script in the remote ...
6
votes
2answers
2k views

List elements with spaces in zsh

I've been studying zsh scripting for all of 2 hours at this point and I've hit a wall. I want to go through a list of files that may have spaces in them. I'm open to completely different approaches ...
5
votes
2answers
860 views

How to tweet using terminal?

I would like to tweet a message using terminal. I tried something like: curl -u 'TwitterUsername':'TwitterPassword' -d status=”Your Message Here” https://twitter.com/statuses/update.xml but seems ...
5
votes
2answers
2k views

Privoxy: blocking twitter, facebook and google outside of their domainslr

Related subject: blocking facebook.com outside facebook.com domain This is from default.filter ################################################################################# # # shockwave-flash: ...
2
votes
4answers
4k views

Need a loop to sleep for a fraction of second

On my machine I need to execute a cycle that iterates 1 simple command that must have a delay expressed in fractions of second. Let's say that I need: to save a file with an increasing enumaration ...
7
votes
3answers
3k views

How to “send” variable to sub-shell?

I run the following script: VAR="Test" sh -c 'echo "Hello $VAR"' But I get : # ./test.sh Hello How can I "send" the variable VAR of my script to the shell created with sh -c?
4
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2answers
2k views

How to copy someone's else folders from public.me.com with a wget-like tool?

How can I copy a folder from http://public.me.com/ (a service related to iDisk, or MobileMe) to my local filesystem with a Unix tool (like wget, a command-line non-interactive tool)? The problem is ...
2
votes
2answers
217 views

How to copy multiple files but keep their extensions the same?

I am looping through a number of files, and $file represents the current file. How can I make copies or renames and keep the extension the same for this current file? e.g. if $file = x.jpg How to ...
2
votes
2answers
2k views

Sed: replacing digits

I am trying to write some install scripts for when I install/upgrade Ubuntu. I'm having trouble with fixing logrotate.d: /var/log/ufw.log { rotate 7 weekly missingok notifempty compress delaycompress ...
1
vote
2answers
324 views

stdout , stderr and logging using the script command

I have remove.sh which contains: rm -v test.tmp And I have install.sh which contains: script remove.log -c './remove.sh' What can I do so that whether or not test.tmp exists, I don't see any rm ...
0
votes
2answers
906 views

Need help to make rows into column with awk or sed

Recently, I look for scripts to take this: This; Is; First; Line; and make it like: This Is First Line
0
votes
2answers
213 views

Autentification on SSH connection in OneLine [duplicate]

Possible Duplicate: Shell Script for logging into a ssh server I need to connect via SSH to a remote server, however I must do this with out interactive mode and with out use Public keys ...
15
votes
3answers
4k views

What does it mean to have a $“dollarsign-prefixed string” in a script?

I just saw this in an init script: echo $"Stopping Apache" What is that dollar-sign for? My research so far: I found this in the bash manual: extquote If set, $'string' and ...
13
votes
7answers
7k views

Faster way than ping for checking if computer online?

I'm writing a wake on lan script for a set of our lab computers. We have sqlite db with a list of the computer hostnames, IPs, and MACs and currently I ping each of them with '-c1' so it doesn't run ...
5
votes
3answers
4k views

History command inside bash script

I have been bashing my head to write a simple history script for the last two days. History is a shell-built in command I couldn't able to use that within a BASH script. So, Is there a way attain this ...
7
votes
1answer
935 views

confirmed exit using trap

I am trying to trap the Ctrl+C signal asking a confirmation from the user. The trapping part works fine. But once the signal gets trapped, it does not return to the normal execution. Instead, it quits ...
4
votes
1answer
1k views

Increase %e precision with /usr/bin/time shell command

When I run the time command in shell time ./myapp I get an output like the following: real 0m0.668s user 0m0.112s sys 0m0.028s However,when I run the command \time -f %e ./myapp I lose ...
4
votes
2answers
450 views

Shell script printing the most visited directories

Is there a way to write a bash script with the following functionalities? Be launched when I press some key or key combination. (not so important requirement) Identify the 7 most visited directories ...
3
votes
4answers
4k views

Backup of LVM2 logical volume

I'd like to make backup on external drive of LVM2 logical volume in dd manner. Approach I consider is to make lv on extranl drive with identical size copy with dd (Please let me know if you see ...
9
votes
4answers
6k views

Script to change current directory (cd, pwd)

I want to run a script to simply change the current working directory: #!/bin/bash cd web/www/project But, after I run it, the current pwd remains unchanged! How can I do that?
6
votes
2answers
353 views

How does this find command using “find … -exec sh -c '…' sh {} +” work?

@StephaneChazelas posted the following solution to this Q&A: Having some trouble using “find -exec {} +”. $ find . -iname "*.extension" -exec sh -c ' exec <command> "$@" <additional ...
6
votes
4answers
3k views

Parallel execution of a program on multiple files

I have a small script that loops through all files of a folder and executes a (usually long lasting) command. Basically it's for file in ./folder/*; do ./bin/myProgram $file > ./done/$file ...
6
votes
2answers
1k views

bash: Piping for loop output prevents local variable modification

First off, sorry for the title. I'm not sure of the correct terminology so if anyone can improve upon it that would be good. I am trying to write a simple bash function that takes, as it's arguments, ...
3
votes
4answers
1k views

passing passwords to a script

I want to scp a file to a remote host, and from there, run a command on the file, and exit the remote session. If I write a usual script, call scp and then ssh, I am prompted to enter two passwords. ...
2
votes
1answer
782 views

Shell script filtering through jpg files attributes

I'm trying to find a way to filter through thousands of jpg files, and keep only the files with a certain attribute (such as the camera brand with which the picture was captured). How can I do so?
9
votes
2answers
3k views

Confusing use of && and || operators

I was skimming through an /etc/rc.d/init.d/sendmail file (I know this is hardly ever used, but I'm studying for an exam), and I've become a bit confused about the && and the || operators. ...
8
votes
2answers
5k views

Invert boolean variable

I want to try simple script flag=false while !$flag do read x if [ "$x" -eq "true" ] then flag=true fi echo "${x} : ${flag}" done But when i run it, if i type true, i will see ...
7
votes
2answers
784 views

sync files recursively between two folders where files are less than 24 hours old

I want to find all the files under a directory which are within 24 hours then rsync those files with another server. There are some old files that I do not want to transfer, however if those old ...
7
votes
6answers
4k views

Extracting nested zip files

I have numerous zip archives, each of which contains a number of zip archives. What is the best way to recursively extract all files contained within this zip archive and its child zip archives, that ...
5
votes
3answers
2k views

The way to use `/usr/bin/env sed -f ` in shebang?

Typing /usr/bin/env sed -f in terminal works. But if use it as a shebang, #!/usr/bin/env sed -f s/a/b/ The script will be fail to execute: /usr/bin/env: sed -f: No such file or directory I ...