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
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5answers
6k views

How to know if /dev/sdX is a connected USB or HDD?

How can I know if /dev/sdX is a local HDD or usb key ? best doing this without root privileges. OK , udevadm helped a lot: For local HDD: udevadm info --query=all --name=sdb | grep ID_BUS E: ...
8
votes
3answers
23k views

Recursive chmod only folders or only files via script or nautilus menu?

This has been discussed before here. What I'd like to know is how to turn these: Recursive chmod only files within this folder: find . -type f -exec chmod 0600 {} \; Recursive chmod only folders ...
6
votes
3answers
271 views

Which bash will expand {1..$VAR} in the same way that zsh does

In response to a comment of mine to this question on SF the OP asserts that the for i in {1..$NUM} expands correctly in bash. I have access to bash 4.0.33 (Ubuntu), 3.2.25 (Centos) and 3.00.16(1) ...
5
votes
2answers
3k views

Manipulate file name piped from find command

I'm relatively new to Bash and am trying to do something that on the surface seemed pretty straightforward - run find over a directory hierarchy to get all of the *.wma files, pipe that output to a ...
5
votes
3answers
1k 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 ...
4
votes
4answers
7k views

Is there an online bash script testing site?

Sometimes I need to help friends with bash scripting. When I'm on a Windows machine, it's a working environment and I can't just setup Cygwin or use a VM. Is there some free scripting website I can ...
4
votes
1answer
1k views

How to run streamripper and mplayer in a split-screen X terminal, via a single script

I want to run streamripper in its own X Terminal (window), then split the terminal horizontally, and then run mplayer in the lower half. This is simple enough to do manually, but getting a script to ...
20
votes
3answers
2k views

How do you enter a directory that's name is only a minus?

I downloaded lessn to my webserver and unzipped it. It contains a folder named -. I assumed I know how to deal with that, but I don't. I tried cd -- -, but that doesn't have the desired effect. ...
19
votes
4answers
5k views

How can I create an alias for a git [action] command (which includes spaces)?

Most of my my aliases are of this form: alias p='pwd' I want to alias git commit so that it does git commit -v But trying to create an alias with a space gives an error: $ alias 'git commit'='git ...
14
votes
2answers
855 views

How can one time out a root shell after a certain period of time?

Is there a way to 'time out' a root shell (for example, in gnome-terminal) so that after a certain amount of time not issuing any commands, the shell exits? I'm searching for a solution that works in ...
13
votes
1answer
5k views

Are there naming conventions for variables in shell scripts?

Most languages have naming conventions for variables, the most common style I see in shell scripts is MY_VARIABLE=foo. Is this the convention or is it only for global variables? What about variables ...
12
votes
3answers
9k views

Comparing two strings in Bash

I have the following if block in my bash script: if [ ${PACKAGENAME} -eq kakadu-v6_4-00902C ]; then echo "successfully entered if block!!" fi The script execution is not entering my if block even ...
12
votes
2answers
9k views

/dev/tcp listen instead of nc listen

With a netcat listener like: nc -l <port> < ~/.bashrc I can grab my .bashrc on a new machine (doesn't have nc or LDAP) with: cat < /dev/tcp/<ip>/<port> > ~/.bashrc My ...
12
votes
5answers
25k views

Using the system date / time in a Cron Script

I'm setting up a Cronjob that will backup a MySQL database I have in my server, but I don't want it to keep overwriting the same file over and over again. Instead, I want to have an array of backups ...
10
votes
2answers
1k views

Closing a file descriptor, >&- vs <&-

In the bash tutorial I am reading, it says that if you open a file descriptor for reading, i.e. exec 3< echolist Then you must close it like this, exec 3<&- However, if you open a file ...
10
votes
3answers
302 views

bash: Some issue when using read <<<“$VARIABLE” on a read-only root partition. Any known workarounds?

Just by coincidence I had to use my ATA-ID-to-device-name script (found here: http://serverfault.com/questions/244944/linux-ata-errors-translating-to-a-device-name/426561#426561) on a read-only / ...
10
votes
4answers
3k views

Batch delete exif info

How can I recursively remove the EXIF info from several thousand JPG files?
9
votes
3answers
2k views

What does “rm is hashed” mean?

I'm going through http://mywiki.wooledge.org/BashGuide/CommandsAndArguments and came across this: $ type rm rm is hashed (/bin/rm) $ type cd cd is a shell builtin Just a little earlier, the guide ...
8
votes
2answers
378 views

How do I columnate a list of items with minimal width?

How do I columnate any uncollumnated input like ls does? ls is creating an optimized table with minimum width for each row, for example: ls 2 dsao file with space with 5 e g ...
8
votes
4answers
785 views

What is the easiest way to execute text from tail at the command line?

Sometimes I'm working on a new (ubuntu) box and I type git and am alerted: The program 'git' is currently not installed. You can install it by typing: apt-get install git-core If that happens I ...
8
votes
4answers
2k views

Abbreviated current directory in shell prompt?

vim has a really nice feature which it utilizes in its paths when they're a bit long: It abbreviates the path to the document in the tab at the top. Is there a way to do something similar to this ...
8
votes
4answers
2k views

How do I find the overlap of two strings in bash? [closed]

I have two strings. For the sake of the example they are set like this: string1="test toast" string2="test test" What I want is to find the overlap starting at the beginning of the strings. With ...
7
votes
2answers
627 views

Why is `tac file | grep foo' (piping) faster than `grep foo < <(tac file)' (process substitution)?

This question was motivated by "Reverse grepping", about grepping a huge file from bottom up. @chaos said: tac file | grep whatever Or a bit more effective: grep whatever < <(tac file) ...
7
votes
3answers
3k views

Use & (ampersand) in single line bash loop

I have been using this command successfully, which changes a variable in a config file then executes a Python script within a loop: for((i=114;i<=255;i+=1)); do echo $i > numbers.txt;python ...
6
votes
3answers
741 views

How can I view a reference or cheat sheet of the basic bash syntax, in the linux terminal?

Every time I need to do a little bash scripting involving if statements, checking for empty variables and non-existent files et.c. I find myself hitting google for some simple bash manual or guide. ...
6
votes
2answers
1k views

How to trigger error using Trap command

I am using Ubuntu 12.04.2. I am trying to use "trap" command to capture abnormal or error in my shell script but I am also trying to manually trigger "Error" exit. I have tried exit 1, but it won't ...
6
votes
3answers
3k views

Configure up-arrow to browse through commands with same initial characters rather than all previous commands

On the bash command-line, ↑ gives me the previous command. On the command-lines in numpy or matlab, when I type a few characters, ↑ gives me the previously entered command starting with those ...
6
votes
4answers
2k views

Colored FIND output?

Is it possible to get colored output from the find command? That is, in the path of each found item, directories are blue, executable scripts are green, et cetera? I'm using version 4.4.2 of GNU ...
6
votes
1answer
1k views

Customizing bash shell: Bold/color the command

There are a number of tutorials/posts online (e.g. http://www.cyberciti.biz/faq/bash-shell-change-the-color-of-my-shell-prompt-under-linux-or-unix/) about how to customize your prompt in bash by ...
5
votes
2answers
186 views

How can I force bash to deallocate a brace expanded variable without name?

For benchmarking, I ran the command: for i in {1..100000000}; do echo "$i" line >> file done Bash expanded the braces and stored the list 1 2 3 4 5 6 ... 100000000 in memory. I thought ...
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 ...
4
votes
4answers
472 views

Place job in background without freeze

Say you start the job like this foo and then desire that you want to place it in background. Typing Ctrl+Z and then bg does the trick but will freeze foo between Ctrl+Z and bg. How can I place foo ...
4
votes
1answer
4k views

dot file not sourced when running a command via ssh

When I run my program interactively, it works fine: ssh somehost $ ~/some/path/somescript.py When I run my program over ssh directly, it doesn't work. The variable PYTHONPATH is not set, because ...
3
votes
3answers
1k views

Detect if mouse button is pressed, then invoke a script or command

Is there any way to get mouse button state from bash? Xdotool can only get mouse location. I'd like to set something up where I can define a rule where when a mouse button is pressed, a script can ...
2
votes
2answers
5k views

What do square brackets mean without the “if” on the left? [duplicate]

As far as I know, square brackets are used to enclose an expression usually in if else statements. But I found square brackets being used without the "if" as follows: [ -r /etc/profile.d/java.sh ] ...
2
votes
3answers
1k views

Kill backgrounded SSH when shell exits

I'm trying to spawn an SSH from my bash profile script that runs in the background for connection sharing (via its control socket). The problem I'm running into is a reliable way to ensure the SSH ...
2
votes
2answers
355 views

How do I prevent a script from terminating when the shell exits?

In particular, I created a script to start Firefox which I double-click and choose 'Run in terminal,' but when the shell exits Firefox is killed immediately. How do I prevent this from happening?
18
votes
1answer
784 views

What does !$ mean?

I'm following through a tutorial and it mentions to run this command: sudo chmod 700 !$ I'm not familiar with !$. What does it mean?
15
votes
3answers
3k views

Changing parent directory (../) with symlinks

I have a symlink ~/link -> ~/a/really/long/path When I do cd ~/link cd .. it takes me to ~ but I want to go to ~/a/really/long Is there a way to do this? I am using bash.
10
votes
3answers
1k views

Why are interactive shells on OSX login shells by default?

In Linux and, to my knowledge, all Unix systems, terminal emulators run interactive, non-login shells by default. This means that, for bash, the started shell will: When an interactive shell that ...
8
votes
2answers
166 views

Why is the ability to definine functions in an enviromental variable not a security risk in itself?

As I understand it, generally it is considered safe to let anyone provide information that will be stored in an environmental variable. The shellshock vulnerability is an issue here because it means ...
7
votes
1answer
494 views

Why does this PS1 value cause unexpected behaviour? [duplicate]

Possible Duplicate: Why is my bash prompt getting bugged when I browse the history? I have set my PS1 variable in .bashrc to be the following: PS1='\e[35m[\W]:\e[0m ' It achieved what it ...
7
votes
3answers
3k views

Reading passwords without showing on screen in Bash Scripts

How to read passwords in bash scripts in a way like tools which are not showing it on terminal ? (Changing font to black on black might be tricky by easy to copy&paste - so it's not solution)
6
votes
4answers
2k views

Why can't we execute a list of commands as different user without sudo?

This question has been asked in a different way in other forums. But there has not been a decent explanation why you can't do the below in bash. #!/bin/bash command1 SWITCH_USER_TO rag command2 ...
6
votes
5answers
2k views

How to make bash put prompt on a new line after cat command?

What I get: host:~ user$ cat example.txt some texthost:~ stas$ What I want to get: host:~ user$ cat example.txt some text host:~ stas$ Is there a way I can make cat behave like this? I'm using ...
6
votes
1answer
338 views

Can I have my shell history record how wildcards expanded?

If I run: $ ls * foo bar buzz $ history | tail -1 ls * You can see that in my shell history it remembers that I ran ls * rather than ls foo bar buzz. Ideally, I'd like to record both in separate ...
5
votes
3answers
1k views

How can I pass argument stored on a variable to WGET

I'm writing a bash script that extensively uses wget. To define all common parameters in one place I store them on variables. Here's a piece of code: useragent='--user-agent="Mozilla/5.0 (Windows NT ...
5
votes
3answers
3k views

Bash script that reads filenames from a pipe or from command line args?

I want my script to read a bunch of filenames (which may have spaces) given either as a glob or from STDIN and do stuff with them. I've been able to read either way separately, but not combine them. ...
5
votes
1answer
5k views

Trouble in script with spaces in filename

I've got a script that scp's a file from remote host back to local. Sometimes the file names contain spaces. scp does not like spaces in its file names. For some reason my attempts at handling the ...
5
votes
2answers
597 views

Use a script parameter in awk

Here is my script (to find the files that contain a specified pattern) : find . -type f -exec awk -v vawk="$1" '/'"$vawk"'/ {c++} c>0 {print ARGV[1] ; exit 0 } END { if (! c) {exit 1}}' \{\} \; ...