Bash

Links with good documentation about bash

• Linux Shell Scripting Tutorial (LSST) v2.0
• Advanced Bash-Scripting Guide
• Shell initialization files
• Great FAQ on BASH

Quoting in bash
There are two types of quoting: strong quotes(' ') and weak quotes(” ”). Strong quotes mean to treat all symbols inside them as literally symbols. Weak quotes treat some special characters as special characters… :) For example dollar sign:

echo "$SHELL" /bin/bash

Also, you can quote a single character using backslash(\), it's called backslash-escaping.

Hot keys in Bash

• Ctrl-z - suspend key, puts the currently running process in background and pause it
• Ctrl-c - kills the current command or process, by sending to it SIGINT(2) signal
• CTRL-\ - stops command
• Ctrl-d - kills the shell an End of file in commands
• Ctrl-m - similar to press enter
• To see al your control keys: stty -a

Builtin variables

• $! - PID of last background job
• $_ - final argument of previous command executed
• $? - exit status of last command
• $$ - Process ID (PID) of the script itself
• $# - amount of arguments
• $0 - the command itself

Read file line by line

while read line
do
echo "$line"
done

Create alias

For example to launch “ls –color” instead of “ls”.In .bashrc file:
alias ls="ls --color"
alias ..='cd ..'
alias d='ls -l | grep -E "^d"'

To redirect standard output and standard error to one file
program > file 2>&1

Logical operations

Double bars || mean logical OR.
For example command2 will be launched only if command1 fails:
command1 || command2

Double ampersands && mean logical AND.
For example, command 2 will be launched only if command1 is successful:
command1 && command2