#!/bin/bash

• csh
• ksh
• sh
• tcsh
• zsh

• bash Built-In Commands
• bash completion
• bsfl
• getopts
• iterm

• ftp://ftp.gnu.org/gnu/bash/
• ftp://ftp.beandog.org/rsyncd/dotfiles/.bashrc.extra - My cross-platform .bashrc.extra :D
• Bash Shell Scripting - 10 Seconds Guide
• Conditional statements
• bash colors
• Bash Hackers wiki
• commandlinefu.com
• Summary of shell facilities
• An A-Z Index of the Bash command line for Linux
• bash Cheat Sheet - some pretty advanced stuff
• Delete All Files In Directory Except Few
• Shellshocker
• Use the Unofficial Bash Strict Mode (Unless You Looove Debugging) - strict mode to help find bugs
• ANSI Escape Sequences
• Bash Pitfalls

• -a and
• -o or
• = or == equal to
• -n string is not null
• -z string is null, that is, has zero length

• -eq number equals
• -ne number does not equal
• -gt greater than
• -ge greater than or equal to
• -lt less than
• -le less than or equal to

• -e file exists (returns false in Bourne shell if file is a symlink)
• -f file is not a directory or device file
• -d file exists and is a directory
• -h file exists and is a symlink (also -L)
• -s file exists and has a size greater than zero
• -w file exists and is writeable
• -x file exists and is executable
• -r file exists and is readable
• -b file is a block device
• -c file is a character device
• -p file is a pipe
• -S file is a socket
• -O you are owner of file
• -G you are group owner of file

Use =~ followed by a regular expression pattern. Do not enclose the pattern in quotes if using in a test block.

Check if a variable is a positive integer:

[[ $1 =~ ^[0-9]+$ ]]

Functions are created and called the same as any shell script: use command line arguments as parameters to pass, and echo any output.

function parse_input() {
   INPUT=$1
   echo "You passed ${1} as an argument"
}

cat filename | while read line; do
  echo "Your line says ${line}"
done

Syntax: ${variable:<starting integer>[:<num characters>]}

string="O hai"
echo ${string:2} # returns hai

Get string length

${#string}
expr length $string

Find the index of the first occurrence of a letter in a string

Returns 0 on not found.

expr index abcdefg d

Strings as commands

You need to use eval to reparse a command through bash.

See here

#!/bin/bash
cmd="date --date=\"1 days ago\""
$cmd         # Doesn't work
eval $cmd    # Works

Simple sed replacement

echo testing testing2 | sed -e 's/ /\|/' # returns testing|testing2

Simple cut with a delimiter, grabbing a field

eix --only-names -Ie bash | cut -d "/" -f 2

• http://www.tldp.org/LDP/Bash-Beginners-Guide/html/sect_03_02.html

• $# - number of bash arguments
• $* - display all variables passed
• $$ - pid of shell, or script being run
• $0 - name of the script
• $! - pid of last job run in background
• $_ - last command run, without the arguments

When setting a variable using the backtick operator, use double quotes around the variable to retain newlines.

files=`ls`
echo "$files"

Get the size of the available cols, lines. Useful when writing shell applications that display output that needs to be paged:

tput cols
tput lines

• mktemp (coreutils) make a temporary file in /tmp

“Wonder piping!” –Shaine

$ true | false | true
$ echo ${PIPESTATUS[*]}

• $# Number of arguments on commandline.
• $? Exit status of last command.
• $$ Process id of current program.
• $! Process id of last backgroundjob or background function.
• $0 Program name including the path if started from another directory.
• $1..n Commandline arguments, each at a time.
• $* All commandline arguments in one string.

You can use trap to capture a signal, such as Ctl-C to kill a command, and then map it to an internal function inside the bash script.

This is useful in scenarios where a shell script calls other scripts, and cancelling them would only cancel that one executed script instead of the main one.

control_c() {
        exit 1
}

trap control_c INT

• Delete: Ctrl W
• Clear Line: Ctrl U
• Start of Line: Ctrl A
• End of Line: Ctrl E

Check to see if input is an integer:

if [[ $1 == ?(-)+([0-9]) ]]; then echo "$1 is an integer"; fi