Command Substitution

Example of command substitution

We can use the output of one command when invoking another command. This is handy when a program’s argument needs to be generated from another program’s output. We can do this with a feature called command substitution. We’ve already seen variable expansion with curly braces, like ${variable}, where the variable’s value is expanded. Command substitution works similarly. With command substitution, the output of the command replaces the command itself. To define a command substitution, we put the command in parentheses instead of curly braces. We saw an example of command substitution in Building Your Prompt when we used the tput ...