Search notes:

shell

Determine if a command is available

if command -v make > /dev/null 2>&1; then
   echo make is available
else
   echo make is not available
fi

Interactive vs non-interactive

An interactive shell accepts input that is typed on a keyboard.

a non-interactive shell executes commands that are stored in a file.

Interactive login shells are started after a successful login (or with bash -l).

If this interactive login shell is Bash, it normally reads /etc/profile and ~/.bash_profile (if available).

The default login shell can be changed with chsh

At least, in bash, if a shell is a login shell can be determined with shopt login_shell.

/etc/shells contains a list of allowed login shells on the system.

When a bash login shell is terminated, bash sources ~/.bash_logout.

Interactive non login shells

An interactive non login shell is usually started from an other login or non-login shell with /bin/bash or su, xterm or konsole.

Non-interacive shells

A non-interactive shell processes the contents of a shell script. It is non-interactive because it doesn't have to wait for input from a user.

TODO

Comments in here documents

Apparently, a clever use of a here document can be used to block comment code in a shell script:

#!/bin/sh

echo before DOC

: <<'DOC'

  This text is apparently not run by the
  shell interpreter. Therefore, it can
  be used like documentation

DOC

echo after DOC

See this stackoverflow answer for more details.