Mastering Linux Shell Scripting - Second Edition

Command substitution

So far, we have seen how to declare variables. These variables can hold integers, strings, arrays, or floats, as we have seen, but this is not everything.

A command substitution means storing the output of a command execution in a variable.

As you might know, the pwd command prints the current working directory. So, we will see how to store its value in a variable.

There are two ways to perform a command substitution:

• Using the backtick character (')
• Using the dollar sign format, like this: $()

Using the first method, we just surround the command between two backticks:

#!/bin/bash 
cur_dir='pwd'
echo $cur_dir 

And the second way is written as follows:

#!/bin/bash 
cur_dir=$(pwd) 
echo $cur_dir 

The output coming from commands ...