Bash:Variables

Bash is a *nix shell. Much more is still in the antiperfect unix site.

echo -n <string>

Print <string> without newline

To check within a startup script (like .bashrc) whether or not Bash is running interactively. Test if $- has an 'i' in it or if $PS1 (the prompt) exists.

case "$-" in
*i*)	echo This shell is interactive ;;
*)	echo This shell is not interactive ;;
esac

if [ -z "$PS1" ]; then
        echo This shell is not interactive
else
        echo This shell is interactive

Arithmetics

Bash and ksh only work with integers.

+, -, *, /, %

add, substract, multiply, divide, modulo.

**

For bash, Exponentiation

10#00012

For bash, force the figure (00012) to be interpreted as decimal. Figures starting with 0 are considered octal by default.

expr <expr>

Voer expr uit, bij boolean wordt 1 (onwaar) of 0 (waar) gegeven

((VAR=x+y))

let VAR=x+y

VAR=$((x+y))

VAR=$(expr x + y)

Calculate and assign to VAR

let VAR+=2

Add two to VAR

Special Parameters

$0

Name current procedure

$1

First passed argument ($2 is the second, $3... )

$*

All arguments given as one string

$@

All arguments given as separate strings per parameter

$#

The number of passed arguments

$?

The returnstate for the last executed command. 0 = OK, all others not.

$$

ProcessID of current process, handy to use for temporary files

$!

ProcessID of last spawned process.