til/ruby/check-return-status-of-running-a-shell-command.md

Check Return Status Of Running A Shell Command

There are many ways to run a shell command in a Ruby context. One of the most common is to place the command inside backticks. It runs the command in a subshell.

The standard output (stdout) from running the command is the return value of the statement. Ruby also captures details about the previously run command in the global $? variable.

> `true`
=> ""
> $?.exitstatus
=> 0

> `false`
=> ""
> $?.exitstatus
=> 1

> `echo 'hello' && exit 2`
=> "hello\n"
> $?
=> #<Process::Status: pid 12284 exit 2>
> $?.exitstatus
=> 2

The value captured in $? is a Process::Status object. It can tell us the exit status of the process with #exitstatus.