Bash

Attention Feminazis

If you are an overzealous feminist and seek documentation for the Bourne Again Shell, type

man bash

at the prompt. (rimshot)

Programming

See also the BASH Programming - Introduction HOWTO.

For

Bash for loops are a little tricky. The general form is

for i in $( ls ); do
  echo item: $i
done

That's how to run a command for every (normal) file in the directory. If you want to make an array yourself, instead of using the lines of a program, that's

for i in {alpha,beta,gamma}; do
  echo item: $i
done

To get a list of files to which you know the extension and want to omit it in the loop, try

for i in $( ls *.png | sed "s/\\.png$//" ); do
...

for .png files. Incidentally, you can strip an extension off of a filename in a variable by doing

$( echo -n $FILENAME | sed "s/\\.png$//" )

Startup files

See shell startup scripts for what to put in these files.

You generally have a choice between .bashrc (see also rc file), .bash_profile, .profile, /etc/profile, et cetera. Here's the gist of what the man basher has to say:

As a login shell

Running as a login shell, bash will always source /etc/profile (if it exists). Then, it selects the first readable file in this order and sources it:

• ~/.bash_profile
• ~/.bash_login
• ~/.profile

Starting login bash with --noprofile makes it skip both /etc/profile and the local profiles.

Incidentally, bash will source ~/.bash_logout upon your logout if it exists.

As a non-login shell

Running as a non-login shell, bash will run ~/.bashrc if it exists. --norc will make it skip the rc file altogether; --rcfile filename will make it source another file instead of ~/.bashrc.