External commands

As a part of the software configuration, you may want to get extra data by running external commands. The basic syntax is the following.

r = run_command('command', 'arg1', 'arg2', 'arg3', check: true)
output = r.stdout().strip()
errortxt = r.stderr().strip()

If check: true is given, meson will error out if command returns with a non-zero exit code. Alternatively, you can set check: false and get the exit code with r.returncode().

Since 0.52.0, you can pass the command environment as a dictionary:

run_command('command', 'arg1', 'arg2', env: {'FOO': 'bar'}, check: true)

Since 0.50.0, you can also pass the command env object:

env = environment()
env.set('FOO', 'bar')
run_command('command', 'arg1', 'arg2', env: env)

The run_command function returns an object that can be queried for return value and text written to stdout and stderr. The strip method call is used to strip trailing and leading whitespace from strings. Usually output from command line programs ends in a newline, which is unwanted in string variables. The first argument can be either a string or an executable you have detected earlier with find_program.

Meson will autodetect scripts with a shebang line and run them with the executable/interpreter specified in it both on Windows and on Unixes.

Note that you cannot pass your command line as a single string. That is, calling run_command('do_something foo bar') will not work. You must either split up the string into separate arguments or pass the split command as an array. It should also be noted that Meson will not pass the command to the shell, so any command lines that try to use things such as environment variables, backticks or pipelines will not work. If you require shell semantics, write your command into a script file and call that with run_command.