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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5
votes
2answers
1k views

dash compatibility to bash

Wikipedia says that dash executes faster than bash. My question is, if I set /bin/sh to dash, will all scripts that use /bin/sh in their shebang line that was intended for bash work under dash?
17
votes
6answers
17k views

Grabbing the extension in a file name

How do I get the file extension from bash? Here's what I tried: filename=`basename $filepath` fileext=${filename##*.} By doing that I can get extension of bz2 from the path /dir/subdir/file.bz2, ...
5
votes
1answer
247 views

Whenever I type some wrong command, my terminal tries to run that command in the background

Something strange started happening to my terminal. Whenever I type some wrong command it tries to run that command in the background. hegeek@colinux: ~# l [9]+ Stopped l thegeek@colinux: ~# ...
2
votes
5answers
4k views

Bash eval array variable name

Here is my bash case: First case, this is what I want to do "aliasing" var with myvarA: myvarA="variableA" varname="A" eval varAlias=\$"myvar"$varname echo $varAlias Second case for array variable ...
49
votes
6answers
36k views

Why doesn't my Bash script recognize aliases?

In my ~/.bashrc file reside two definitions: commandA, which is an alias to a longer path commandB, which is an alias to a Bash script I want to process the same file with these two commands, so I ...
14
votes
7answers
8k views

bash directory shortcuts

When I type cd ~foo, I'd like bash to take me to some directory foo as a shortcut for typing the full directory path of foo. and I'd like to be able to cp ~foo/bar.txt ~/bar.txt to copy a file from ...
5
votes
1answer
7k views

Remote for-loop over SSH

I have the following in a script for server in ${servers[@]}; do echo ${server} ssh user@${server} "for i in /tmp/foo* ; do echo ${i}; done" done But it doesn't work. Weird thing, I see $I amount ...
1
vote
1answer
96 views

How do I make the “1.9.2” Ruby string point to the final release with RVM?

I'm using RVM to manage my Ruby environment on OSX, and currently it's interpreting '1.9.2' as ruby-1.9.2-rc2 instead of the final release. How can I update this to make it behave as expected?
4
votes
3answers
9k views

Convert ascii code to hexadecimal in UNIX shell script

I'd like to convert ASCII code (like - or _ or ., etc.) to hexadecimal representation in the Unix shell (without bc command), eg : - => %2d. Any ideas?
170
votes
11answers
48k views

Preserve bash history in multiple terminal windows

I consistently have more than one terminal open. Anywhere from two to ten, doing various bits and bobs. Now let's say I restart and open up another set of terminals. Some remember certain things, some ...
10
votes
5answers
6k views

Run a script via cron every other week

I've done quite a bit of research in how to do this, and I see there's no direct way in cron to run a job, say, every other Thursday. Right now, I'm leaning toward making a script that will just run ...
4
votes
2answers
443 views

Scheduling command/script by specifying the exact second

I'm using bash and wondering how I can execute a command/script at a later specified time, with the accuracy of a second? I read the man page for the at-command, but as far as I could understand it's ...
20
votes
7answers
3k views

how to glob every hidden file except current and parent directory [duplicate]

I want to glob every hidden file and directory, but not the current (.) and parent directory (..). I am using bash. Observe current behaviour: $ ls -a . .. ...a ...aa ..a ..aa .a .aa .aaa ...
32
votes
10answers
13k views

Batch renaming files

I have a directory full of images: image0001.png image0002.png image0003.png ... And I would like a one-liner to rename them to (say). 0001.png 0002.png 0003.png ... How do I do this?
4
votes
1answer
195 views

How can I make Ubuntu UI uniformly use bash keyboard shortcuts?

On my default 10.04 Ubuntu install I am consistently tripped up by the fact that some UI text areas/input boxes treat CtrlA as "select all" vs. "move my cursor to the beginning of the line." Is there ...
7
votes
2answers
22k views

su options - running command as another user

I was wondering how to run a command as another user from a script. I have the script's owner set as root. I also have the following command being run within the script to run the command as the ...
3
votes
2answers
629 views

Block specific IP from accessing gateway

Suppose you are on linux internet gateway/router. What would you do to block a client with specific IP using bash script. I prefer something like ./block_client.sh 192.168.1.123 to block and ...
18
votes
2answers
2k views

Display stuff below the prompt at a shell prompt?

Lets's say my prompt looks like this (the _ represents my cursor) ~ % _ Is there any way I could make it look like this ~ % _ [some status] The question was originally about zsh, but now has ...
3
votes
2answers
580 views

How can I apply caret-substitution to my nth-last command?

I regularly find myself having to execute a lengthy command on a file, then process the results with other commands. To process the next file, I usually rerun the same command by hitting the Up key ...
42
votes
4answers
4k views

What features are in zsh and missing from bash, or vice versa?

As a Linux user, I've always just used bash because it was the default on every distro I used. People using other Unix systems such as BSD seem to use other shells far more frequently. In the ...
8
votes
7answers
29k views

Which shell should I use - tcsh vs bash? [closed]

I have been using tcsh for a long time now. But whenever I am searching for something, I often find that the methods specified are bash specific. Even the syntax for the shell scripts is different for ...
29
votes
7answers
2k views

How to determine where an environment variable came from

I have a linux instance that I set up some time ago. When I fire it up and log in as root there are some environment variables that I set up but I can't remember or find where they came from. I've ...
4
votes
8answers
776 views

Write a remote managing script

I need to be able to locally run a script that will connect to various servers and run commands on them. What is the best way to accomplish this?
11
votes
5answers
2k views

Using text from previous commands' output

EDIT April, 2015: If you have this same question I recommend also checking http://xiki.org/ I know this is not how terminals work, but I find myself often wishing there was an easy way of using ...
98
votes
11answers
121k views

Colorizing your terminal and shell environment?

I spend most of my time working in Unix environments and using terminal emulators. I try to use color on the command line, because color makes the output more useful and intuitive. What options exist ...
26
votes
7answers
7k 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?
11
votes
3answers
3k views

bash find xargs grep only single occurence

Maybe it's a bit strange - and maybe there are other tools to do this but, well.. I am using the following classic bash command to find all files which contain some string: find . -type f | xargs ...