The shell is unix's command-line interface. You can type commands in a shell interactively, or write scripts to automate tasks. Use this tag for questions applying to /bin/sh and most compatible shells (ash, bash, ksh, zsh, …).

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2
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2answers
129 views

In-place substitution for lines matching some pattern in a given set of files

Following on from my previous question: Remove slashes/parent paths from filenames inside CSS and Javascript content I arrived at the following command which replaces any filenames in these ...
3
votes
2answers
763 views

Remove slashes/parent paths from filenames inside CSS and Javascript content

I need to go through all my css and js files and if there is a filename referenced that has any slashes (/) at all then the slash should be removed. What I want is: if any files referenced are ...
4
votes
1answer
1k views

shopt -s nocaseglob is not working on Ubuntu

Case insensitive file name globbing is not working in bash on Ubuntu 11.04 64bit. The shell options specified in .bashrc are as follows: shopt -s nocaseglob shopt -s nocasematch shopt also shows ...
6
votes
2answers
1k views

redirection and pipeline

I was wondering about differences and relation between redirection and pipeline. Is pipeline only used to connect stdout output of a command to stdin input of another command? Is redirection only ...
6
votes
2answers
128 views

understand a sequence of redirections

If several redirections are used together, does changing their order make difference? How shall one understand the meaning of their order? Is the chained channel of redirections built as reading the ...
25
votes
4answers
30k views

Usage of dash (-) in place of a filename

For a command, if using - as an argument in place of a file name will mean STDIN or STDOUT. But in this example, it creates a file with the name -: echo hello > - How can I make - in this ...
1
vote
2answers
263 views

Weird executabe behaviour

I have a server machine with ubuntu 9.10. I am trying to put in place an executable, which turns out to be the latest flashplayer (debugger version). Somehow the file appears as present and ...
4
votes
3answers
486 views

General specification for command line interface

I was wondering where I can find and learn some general idea about the command line interface used in Linux and bash? As to now, I have found pieces of such information only from experience, such as ...
-1
votes
3answers
668 views

calling functions within a function

I need to fetch the results of different time ranges and email the results, but i am having trouble with the email part of the script, how can i send an email with both results? (15min range and ...
9
votes
2answers
6k views

What is the significance of single and double quotes in environment variables?

I defined some environment variables in my .profile like this: MY_HOME="/home/my_user" but the variable does not seem to evaluate unless I strip off the quotes and re-source the file. I believe ...
4
votes
3answers
2k views

Is there a tr for translating into longer strings?

tr is great for translating a set of characters to another set of characters. Sometimes, I want to translate a set of characters to a set of strings, e.g. all < and > to &lt; and &gt;. ...
6
votes
3answers
402 views

Why might tmux only be capable of attaching once per shell session?

I'm using tmux on a Fedora 8 server (workplace restriction) to monitor several boxes on a stress rack. I noticed that I can only attach to my detached tmux session once per shell session. In order ...
8
votes
3answers
11k 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:
4
votes
4answers
157 views

Make mistakenly thinks rule succeeded because of 0-sized file generated by output redirect

In a makefile, I have several rules that look like this: out.txt: foo.sh input.txt ./foo.sh -i input.txt > out.txt If foo.sh fails, then out.txt will be created as a 0-sized file. If I run ...
17
votes
3answers
9k views

Bash: double equals vs -eq

I am doing integer comparison in bash (trying to see if the user is running as root), and I found two different ways of doing it: Double equals: if [ $UID == 0 ] then fi -eq if [ $UID -eq 0 ] ...
2
votes
3answers
4k views

grepping a variable and adding 1 to it

I have a variable containing a leading zeroes number, and I want to grep this variable and that same variable plus one. I made several attempts but ran into errors. Here's what I want to do: read var ...
12
votes
4answers
1k views

How did they manage to drive a Unix computer before mice and copy & paste?

Since Unix is 40 years old, Unix is older than the invention of the computer mouse. (actually only 3 years if Unix is from 1969 and the mouse from 1972) How in the world did a new user do anything ...
4
votes
3answers
320 views

Why do you need the “./” when executing programs in the current directory? [duplicate]

Possible Duplicate: Why do we use “./” to execute a file? It seems redundant and gets annoying after a while -- is there a way to change this? If not, can somebody explain the ...
4
votes
1answer
211 views

Why first set a variable and then export it instead of setting and exporting in one command?

If gpg-agent is executed, it outputs data that can be processed by a shell directly, e.g.: SSH_AUTH_SOCK=/tmp/ssh-apeOFqMF3292/agent.3292; export SSH_AUTH_SOCK; SSH_AGENT_PID=3293; export ...
6
votes
2answers
4k views

Howto create a permanent client connection with netcat?

I'm writing a bash script that constantly read a folder in a loop to send data to a server at a defined time interval. I'm using netcat as the tool to connect to the server and send the data. My ...
3
votes
1answer
525 views

Writing a bash script for apache conf files

I'm trying to automate creating vhosts on my computer. This is merely a learning experience for bash scripting. I'm currently novice. I'm trying to learn more about awk, sed. No, this isn't homework. ...
3
votes
3answers
3k views

Pass the background flag (&) through expect and ssh

My command line/bash fu is extremely weak, but I'm trying to hone my abilities. Hopefully someone can help. I wrote a super simple expect script so that I can SSH in to a headless box we're using at ...
8
votes
5answers
798 views

IO redirection and the head command

I was trying to quickly edit an .hgignore file from the Cygwin bash shell today, and I added a line that was a mistake. I'm not sure if this was the best way to do it, but I quickly thought of using ...
9
votes
1answer
1k 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 ...
1
vote
2answers
1k views

Delete files recursively that DON'T match regexp

I'm attempting to clean out a bunch of temporary files from a folder tree, but don't want to delete files that match some criteria, specifically executable files, .tpl files, and not the subfolder ...
8
votes
2answers
5k views

See the STDOUT redirect of a running process

If I start an app with this command: /path/to/my/command >> /var/log/command.log And the command doesn't return, is there a way, from another prompt, to see what the STDOUT redirect is set ...
6
votes
2answers
823 views

How to detect if input is from argument, file or terminal

In bash, is there a way to know if a given script has been invoked with: $ myscript.sh myfile or: $ myscript.sh < myfile Inside some scripts I always have accessed the contents of myfile with ...
4
votes
1answer
296 views

Program to filter lines by passing them to an external program?

I'm looking for a program to use an external program to filter the lines of a stream - pretty much a version of grep that, for each line, prints or suppresses it based on whether the specified program ...
5
votes
4answers
2k views

Why can't I get the exit values of a command in this bash script?

So I was writing this little nautilus script for transcoding video into mp3: #! /bin/bash -x if [ -z "$1" ] then zenity --warning --text="Error - No file selected !" exit 1 fi ...
2
votes
2answers
323 views

How to update a content management installation by overwriting existing files via ssh and shell?

I have installed a cms (modx) on a webserver running CentOS 5 and Apache 2.2. Now there is a new version and I would like to update it. The instructions in the modx-wiki suggest to overwrite the ...
5
votes
1answer
1k views

How to pipe the result of 'date' command to 'mv' command

I want to rename my file to the current timestamp.I know how to get the current timestamp("date +%s") but how can I pipe it to 'mv' command?
2
votes
3answers
12k views

Executing a shell command from PHP with shell_exec

Included in my thesis is to create an administration interface, in which an administrator can approve users whom have asked for access to use OpenNebula. Upon approval the users should be added to ...
2
votes
1answer
544 views

why isn't xargs parsing my input correctly?

Ive been trying to write a shell script that will interface with cmus and then notify me of the track info using notify-send. Right now it is not working mainly because xargs does not seem to pass 2 ...
8
votes
4answers
7k views

How to print all printable ASCII chars in CLI?

How can I list all the printable ASCII characters in the terminal?
1
vote
4answers
487 views

Fast incremental searching of files from shell

I like the command-t script in vim editor that is able to intelligently and incrementally search for files. Is there some similar program that is able to search from shell? It would be great if it ...
10
votes
6answers
918 views

Why was the word “shell” used to descibe a command-line interface?

I'm curious about the term "shell." I think I know what it is (though the distinction between "shell" and "terminal" is still fuzzy) but why was the word "shell" chosen to describe this type of ...
3
votes
2answers
2k views

Is there a way to push shell config information when SSHing to a host?

I know how to set the GNOME-terminals (or xterms!) prompt to green/red regarding the last exit code: vi .bashrc export PROMPT_COMMAND='PS1="` if [[ \$? = "0" ]]; then echo "\\[\\033[0;32m\\]"; else ...
4
votes
3answers
546 views

mkdir based on input from other directories

I have a directory full of albums I've ripped to FLAC format. Folders are named "Artist - Album [flac]" I need to create matching directories named "Artist - Album [mp3]" but only for certain ...
7
votes
1answer
9k views

How to reset a shell environment?

This issue has been bugging me for a while, and although I've taught I've found my answer through EnvWatcher, unfortunately it only works on Bash. And I use zsh. I would like to replicate the things ...
4
votes
4answers
9k views

What is a command line alternative to top for finding current CPU utilization that isn't dependent on screen width?

If I run top -p <myPID> -n 1 with a terminal that isn't wide enough, the CPU utilization % is omitted from the output. When trying to find a process' cpu utilization via bash scripting, this is ...
2
votes
1answer
535 views

How do I make a droplet/.app in platypus for my unix command?

This is my sample code from the platypus tutorial. I am trying to make it work with a command named pymol, and I want it to open .pdb files or open just pymol. I know nothing about perl, but I have ...
4
votes
2answers
5k views

changing current working dir with a script

I've read this question and answer, but it doesn't quit fit my problem, even tho it's similar. I'm writing a script (called cpj) that will launch one of my current projects. I have about 5 of them. ...
4
votes
3answers
481 views

script to use the output of a command (ls) and use it in another command

I have a collection of pdf files I would like to convert to epub. I know Calibre's command ebook-convert will do the trick (nicely might I add). However I have more than one file. I'd like to be able ...
1
vote
4answers
352 views

Faster delayed execution than 1 minute?

I am working on a program that can "upgrade itself" by install a new package. In order to accomplish this, I am using the at command to specify that a shell script should be run one minute in the ...
0
votes
2answers
2k views

How to generate random IP addresses

$ nmap -n -iR 0 -sL > RANDOM-IPS-TMP.txt $ grep -o "[0-9]*\.[0-9]*\.[0-9]*\.[0-9]*" RANDOM-IPS-TMP.txt | egrep -v "10.*|172.[16-32].*|192.168.*|[224-255].*" > RANDOM-IPS.txt egrep: Invalid ...
9
votes
2answers
7k views

How to make exported shell variables permanent?

export LD_PRELOAD=/usr/lib/libtsocks.so It's ok that I can export in this way, but how can I make it permanent? I want LD_PRELOAD to still be changed after a reboot. I'm using Ubuntu and Fedora
1
vote
1answer
369 views

Which process/program create/write the file which I/O is redirected to?

When learning SELinux, I executed semanage fcontext -l > fcontext.txt under /root directory to dump massive fcontext information to a file. The funny result is: fcontext.txt was created, but the ...
3
votes
1answer
510 views

Git - remove deleted files

I'm using this simple git alias rmdel = "!git rm $(git ls-files -d)" meant "remove deleted", i.e. to remove from the staging area all files deleted from the file system. It works fine except ...
84
votes
13answers
34k views

Get exit status of process that's piped to another

I have two processes foo and bar, connected with a pipe: $ foo | bar bar always exits 0; I'm interested in the exit code of foo. Is there any way to get at it?
3
votes
2answers
764 views

Cut on both characters and field

I have a record like : 2011-05-29 17:51:34 => 'HS|CMGC|RN431|CI13950|CH7-4a37-afe2-acabfc9d262d|DA110529|TI175133|' I want my final output to be something like: 2011-05-29 17:51:34 CI13950 I ...