Intro To 'true' Command In Linux

2023-05-20 - By Robert Elder

     I use the 'true' command which does absolutely nothing and then exits successfully:

true

     The 'true' command can be built into the shell or it can exist as a regular executable:

type -a true

true is a shell builtin
true is /usr/bin/true
true is /bin/true

Return Code 0 == 'Success'

     Just like many other commands, whenever you run the 'true' command it will exit with a successful return code:

true

     You can verify this by echoing the dollar sign question mark variable and then observing the value of 0 which indicates a successful program exit:

echo $?

0

Use Case Of 'true' Command

     The 'true' command is useful whenever you must specify a program that should exit successfully.  Here is a while loop that will print hello world forever:

while /bin/true; do echo 'Hello World!'; sleep 1; done

     And the output will look like this:

Hello World!
Hello World!
Hello World!
Hello World!
... Message repeated every 1 second forever.

     The 'while' keyword in bash will continue to run the loop as long as the command exits successfully, and that's exactly what the 'true' command always does.

     That's why the 'true' command is my favourite Linux command.

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