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Help File Library: Bash Scripting Cheat Sheet

Written By: ph34r

A quick cheat sheet for programmers who want to do shell scripting. This is not intended to teach

programming, etc. but it is intended for a someone who knows one programming language to

begin learning about bash scripting.

Basics

All bash scripts must tell the o/s what to use as the interpreter. The first line of any script should

be:

#!/bin/bash

You must make bash scripts executable.

chmod +x filename

Variables

Create a variable - just assign value. Variables are non-datatyped (a variable can hold strings,

numbers, etc. with out being defined as such).

varname=value

Access a variable by putting $ on the front of the name

echo $varname

Values passed in from the command line as arguments are accessed as $# where #= the index of

the variable in the array of values being passed in. This array is base 1 not base 0.

command var1 var2 var3 .... varX

$1 contains whatever var1 was, $2 contains whatever var2 was, etc.

Built in variables:

Variable Use

$1-$N Stores the arguments (variables) that were passed

to the shell program from the command line.

$? Stores the exit value of the last command that was

executed.

$0 Stores the first word of the entered command (the

name of the shell program).

$* Stores all the arguments that were entered on the

command line ($1 $2 ...).

"$@" Stores all the arguments that were entered on the

command line, individually quoted ("$1" "$2" ...).

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Red Hat NETSCAPE MANAGEMENT SYSTEM 6.0 - COMMAND-LINE Instrukcja Użytkownika Strona 35