GNU/Linux Command-Line Tools Summary

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6.3. Command Substitution

Command substitution is basically another way to do a pipe, you can use pipes and command substitution interchangeably, it's up to you which one you find easier...

Command substitution can be done in two distinct ways.

   


• Method One (back-quotes)
   

Simply type:


   

command_1 'command_2 -options'

This will execute “command_2” and it's output will become the input to “command_1”.


       Backquote key
        

The back-quote key is usually located at the same place as the tilde, above the [Tab] key.



• Method Two (dollars sign)
   

Simply type:


   

command_1 $(command_2)

This will execute “command_2” and it's output will become the input to “command_1”.



• Using the pipe instead
   

You can of course use pipes to do the same thing, if you don't know what a pipe is, please see Section 6.2 . For example instead of doing:


   

less $cat file1.txt file2.txt

You could do:


   

cat file1.txt file2.txt | less

And end up with exactly the same result, it's up to you which way you find easier.

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