Questions about bash only, as opposed to other Bourne/POSIX shells. For all Bourne/POSIX-style shells, use the /shell tag instead.

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8
votes
3answers
7k views

bash: Use a variable to store stderr|stdout redirection

Is there any way to redirect stdout and stderr via variable like adding command options in script? For example I have a script: #!/bin/bash -x TEST=">/dev/null 2>&1" OPT='-p -v' mkdir $OPT ...
4
votes
1answer
387 views

Custom bash completion with directories and a fixed set

I'm trying to setup a bash completion, and have two problems For parameter one, I needed a completion for directories For parameter two, a fixed array for completion, I just don't know how to let ...
7
votes
3answers
2k views

How can I find what is interfering with CTRL+F?

I'm running LinuxMint12 with Gnome with Cario-Dock and I have a logitech G15 keyboard. I set up a bash script with the extra keys to take the active window, resize it, and move it to a specific ...
3
votes
5answers
198 views

gnome-dictionary no-window option does not work

I would like to have a bash dictionary so I found gnome-dictionary. However, just typing gnome-dictionary will bring up a GUI box. In gnome-dictionary --help, and in the man file, it says a -n or ...
3
votes
3answers
610 views

Escaping argument in bash script?

I'm writing a bash script wherein I want to check that one of the arguments passed to it is a valid group. I have the line if [ `grep -c -e '\b$2\b' /etc/group` -eq 0 ]; then echo "Error: $2 is ...
7
votes
2answers
3k views

Screen status bar to display current directory for zsh/bash shell

I use GNU screen a lot with zsh as my shell. It would be a nice feature (I think) to be able to display the current directory name (not the full path) as the tab title. I can do that with CTRL+A ...
2
votes
1answer
498 views

Script that unpacks a initrd, allows editing of the preseed.cfg and the packs it to cpio and gzip again

I want to program a script that allows what is said in the title. So basically I gunzip the initrd, than unpack the cpio, open vi to allow editing, save, pack with cpio, and gzip again, so nothing ...
0
votes
1answer
587 views

Directory diff in bash script

I have a bash script that expands two archives (jar files) into two directories and then does a diff of the two folders. I want the diff to be piped into a file so I do this in the bash file. diff -r ...
5
votes
1answer
1k views

Autocomplete of filename in directory

This question is quite similar to this one, but I can't understand the solution. I also know this tutorial, but still I am unable to understand what I am doing wrong. I am trying to autocomplete the ...
3
votes
3answers
411 views

Automatic cleanup of Bash history

How can Bash history be automatically cleaned up? For example Remove detectable typos from history (ls-lh does not show up in which, so it is removed, I meant to type ls -lh) Clean excessive spaces ...
2
votes
2answers
140 views

Bash completion for `unset` command

How can I setup bash completion for the unset command, like when you use echo $XXX, you can get a completion for XXX?
1
vote
1answer
1k views

Capture user input while doing other things

Is there a way to have the output of a subprocess (something other than 'sleep' below) be dovetailed with the output from a foreground command-loop? For example: while true do echo "updating ...
2
votes
3answers
2k views

Ignore or catch division by zero

How do I ignore the division by zero error in Bash? Example 1: (Doesn't work) echo $((1/0)); echo "yay"; echo $((1/0)) || echo "yay"; Example 2: echo -n $(echo -n $((1/0))) 2> /dev/null; echo ...
1
vote
4answers
1k views

Checking for the existence of files against a list

I have a "command" text file that issues a data file download command on each line. I send the command file to bash. However, a small percentage of the downloads fail. Here is the algorithm I ...
4
votes
4answers
454 views

Show output on another “screen” and return to normal when done

I want a similar behavior as less vim nano etc. uses. Is this possible to achieve with bash?
6
votes
1answer
2k views

How do I get the difference between two timestamps?

I am creating a simple backup script. I would like to have a message saying "You last backed up x days ago" on login. I can create a file when I do the backup "backup/.last_backup_timestamp" but what ...
11
votes
4answers
2k views

Is it possible to configure ctrl-w (delete word)?

Normally, Ctrl-w deletes back to the last whitespace. Is it possible to configure it to use additional characters, such as /? Edit: To be more clear: I don't want to configure the key for it, I want ...
6
votes
1answer
1k views

Why bash time is more precise then GNU time?

The buitin bash command time gives milisecond precision of execution and GNU time (usually /usr/bin/time) gives centisecond precision. The times(2) syscall gives times in clocks, and 100 clocks = 1 ...
11
votes
4answers
1k views

How do I choose specific files in a different directory using bash?

I want to list (or delete, or do some other operation) on certain files in a directory, like this: $ ls /opt/somedir/ aa bb cc aa.txt bb.txt cc.txt $ ls /opt/somedir/(aa|bb|cc) ## pseudo-bash ...
3
votes
3answers
2k views

After installing oh-my-zsh: … /.zshrc:source:34: no such file or directory … /.oh-my-zsh/oh-my-zsh.sh

I just tried to install oh-my-zsh. I get the following error when I try to run rvm: zsh: command not found: rvm I also get the following error when I try to open a new tab: ...
5
votes
3answers
503 views

Is there a shortcut in bash to delete the last segment of a path?

I've become pretty proficient with a number of bash shortcut keys that make my bash-ing faster: C-a/C-e, C-u, C-w, M-f/M-b, C-r etc. One common task that I haven't found a good shortcut for though is ...
1
vote
3answers
438 views

Customize the way stderr is appended to a file

I have an issue with a shell script that uses rsync to synchronize 2 directories. I'm storing the result of the rsync command (whether it's successful or not) to a file named status and in case there ...
2
votes
1answer
772 views

Remap bash vi keys?

I use Dvorak and vi, so when I found out about the vi mode in Bash, I was very excited. However, it would be even better if I could remap the movement keys to be the ones that I use in vi (I swap keys ...
5
votes
1answer
2k views

In Bash, why is PROMPT_COMMAND set to something invisible?

On RHEL6 and CentOS 6, /etc/bashrc sets PROMPT_COMMAND here: case $TERM in xterm*) if [ -e /etc/sysconfig/bash-prompt-xterm ]; then PROMPT_COMMAND=/etc/sysconfig/bash-prompt-xterm ...
2
votes
2answers
95 views

How to output only given chars?

How can I crop unneeded chars, and only output what I need? For example: input: ASDFQWER output: DFQ I mean in this case I need only the 3.-4.-5. chars of the string. How do I do that?
7
votes
2answers
459 views

How to do block selection in `screen`

In vim, there's a CtrlV to do block selection. How can I do it in screen?
6
votes
3answers
3k views

How to setup trap in bash functions?

I can setup trap in bash scripts but not bash functions. For example, source the code below and run f, now try Ctrl+C, it's not been trapped! How to setup trap in bash functions? 4 trap ctrl_c ...
5
votes
1answer
237 views

Why is the following command killing a system?

Anyone understand the following code , running in bash ? :(){ :|:& };: It seems to be a "fork" bomb on Linux.
1
vote
1answer
206 views

Tab and complete

Is the key binding for tab to complete in the readline settings set implicitly. Because when I outputted bind -q complete I got this in return complete can be invoked via "\C-i", "\e\e". ...
2
votes
0answers
299 views

What happens when you background a function which calls another function?

Question says it all on the tin. Can someone explain to me what goes on here ? I'm trying to find out how to background a process in a script that calls another function and reliably terminate it when ...
1
vote
1answer
441 views

How to demux audio and know what type it is?

How to demuxed audio and know what type it is? When muxing an audio into a video, ffmpeg, mencoder, etc require to know what the audio's encoding is. The encoder typically uses the file name's ...
5
votes
2answers
673 views

Setting readline variables in the shell

I read in the man page, that you set readline parameters on an off or to a value by using set var value Is this the same as the set builtin, and how do you set the variables once inputrc has already ...
20
votes
4answers
28k views

What does ` (backquote/backtick) mean in bash?

I came across the following command sudo chown `id -u` /somedir And I wonder what is the meaning of the ` symbol. I noticed for instance that while the command above works well the one below does ...
8
votes
3answers
10k views

Bash - test for newline?

In various places around the web I've found: \015 \012 \x0a - hex \n \r all as synonyms for various newlines / carriage returns... But in this small script I cannot recognise when I come across a ...
2
votes
4answers
931 views

Bash options and interactive shells

The -s option to bash doesn't seem to really do anything When I execute commands with or without it nothing changes. What really confuses me is when I execute a shell script I always seem to be ...
1
vote
2answers
211 views

conditional expression and expansion

I don't seem to understand how to "test" the conditional operators [[ and [. I tried using various form such as echo [[a=a]] [[a=a]] echo $? and some other things I want to see what they ...
9
votes
4answers
9k views

How do I reverse a for loop?

How do I properly do a for loop in reverse order? for f in /var/logs/foo*.log; do bar "$f" done I need a solution that doesn't break for funky characters in the file names.
2
votes
2answers
289 views

Why does “$i | sed” not work?

I have this code: if [ $i | sed -e "s/^.*\(.\)$/\1/" = "/" ] then echo "folder" else echo "file" fi where $i is something like this app4/ The code above should get the last char of the ...
2
votes
1answer
347 views

Get pid of long running command executed via at

I would like to spawn a persistent netcat server. My command of choice is the following: echo "bash -c \"while [ 1 ]; do nc -l -p 1111 >> check; done\"" | at now I am wondering how I can get ...
-2
votes
1answer
270 views

Why does this script show all files in the directory and not just PDF files?

I wrote the script below to find the number of PDF files in a given directory. However, it instead shows all the files in the directory: #!bin/bash message="." message1="*.pdf" ls -al $message ...
3
votes
3answers
739 views

Is it a script or is it a binary?

At the end, it looks like it's just a regular sh script: [USER@MACHINE ~/Desktop/D] head -2 truecrypt-7.1-setup-x86 #!/bin/sh CHECKSUM=163123652 but @the scripts end: [USER@MACHINE ~/Desktop/D] ...
2
votes
2answers
1k views

Is the `\` character escaping or becoming part of my ssh key password

If I do: ssh-keygen -N password123\$ -f bobskeys Is \ escaping the $ character or becoming part of the password? Or rather, will bash be doing any escaping before ssh-keygen gets the password ...
5
votes
2answers
2k views

Is it possible to get the error message from previous command which failed when the conditional command runs using ||

I have a helper function: function error_exit { /opt/aws/bin/cfn-signal ... exit 1 } This helper function is used to signal an error. Here is an example of usage: /opt/aws/bin/cfn-init -s ...
3
votes
1answer
596 views

wait for autossh connection to complete

I'm trying to create a script that runs a few commands that take a long time to execute and require a constant connection, but autossh user@server wait $! #or wait ${!} commandA commandB doesn't ...
0
votes
1answer
631 views

-bash: command: command not found [closed]

I'm trying to run a program from the command line, and I got a -bash: command: command not found error. What can I do to troubleshoot/fix the problem?
11
votes
4answers
12k 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?
2
votes
0answers
109 views

How do I get this Bash-script to work? [duplicate]

Possible Duplicate: How to name a file in the deepest level of a directory tree How do I get this script to work? The goal is to find the directory at the deepest level in the directory ...
2
votes
2answers
972 views

su - username -c “./script.sh” -> no such file or directory

We have: a user nico. a folder /home/nico/script_home with some bash scripts: main.sh subscripta.sh sqlscripta.sh We connect as root and cd /home/nico/script_home/ Finally we run ./main.sh We ...
14
votes
5answers
11k views

#!/bin/bash - no such file or directory

I've created a bash script but when I try to execute it, I get #!/bin/bash no such file or directory I need to run the command: bash script.sh for it to work. How can I fix this?
6
votes
1answer
491 views

“Safe mode” on Linux?

Under RouterOS/Cisco there is a function called "safe mode". When someone presses CTRL+X then the terminal goes in "safe-mode" that meant that if the terminal exists in a "bad way", ex.: the user ...