Substitution

Substitution is a feature of the bash shell that allows you: =Storing output to variables= Imagine you got that little command line from bash_tips that outputs your IP-address: duffman:~ # ifconfig eth1 | sed -rn 's/^.*inet addr:([^ ]+).*$/\1/p' 192.168.0.6 Now, you want your IP address stored into a variable, say, you want to substitute the commandline by its output and store it to a variable. Use the operator $ to do this: duffman:~ # ip=$(ifconfig eth1 | sed -rn 's/^.*inet addr:([^ ]+).*$/\1/p' ) duffman:~ # echo $ip 192.168.0.6 duffman:~ # The operator $ executes the statement that is within its paranthesis and substitutes itself with the output of that statement. The operator ´´ (backticks) do the same, but they are not cascadable.

=Getting a list of files= The operator * is substituted by all files in your current folder, e.g. ls * behaves the same as ls file1 file2 file3

=See also=
 * stdin
 * stdout
 * stderr
 * piping
 * Redirection
 * Bash-operators