Ruby: Call Bash commands, run shell scripts

Ways to execute a shell script

cmd = "echo 'hi'" # Sample string that can be used

1. Kernel#`, commonly called backticks – `cmd`

This is like many other languages, including Bash, PHP, and Perl

Returns the result of the shell command


value = `echo 'hi'`
value = `#{cmd}`

2. Built-in syntax, %x( cmd )

Following the x character is a delimiter, which can be any character. If the delimiter is one of the characters ([{, or <, the literal consists of the characters up to the matching closing delimiter, taking account of nested delimiter pairs. For all other delimiters, the literal comprises the characters up to the next occurrence of the delimiter character. String interpolation #{ ... } is allowed.

Returns the result of the shell command, just like the backticks


value = %x( echo 'hi' )
value = %x[ #{cmd} ]

3. Kernel#system

Executes the given command in a subshell,

Return: true if the command was found and ran successfully, false otherwise


wasGood = system( "echo 'hi'" )
wasGood = system( cmd )

4. Kernel#exec

Replaces the current process by running the given external command.

Return: none, the current process is replaced and never continues


exec( "echo 'hi'" )exec( cmd ) # Note: this will never be reached beacuse of the line above

Extra Advice

$?, which is the same as $CHILD_STATUS, accesses the status of the last system executed command if you use the backticks, system() or %{}. You can then access the exitstatus and pid properties


More Reading