Function cmd

build.py:46–82

Run a command. If quiet is True, or if V is not set in the environment, eat its stdout and stderr by default (we'll print both to stderr on any failure though). If V is set and we're not forced to be quiet, just let stdout and stderr flow through as usual. The name V is from

(cmd, quiet=False, shell=False)

def cmd(cmd, quiet=False, shell=False):
    """
    Run a command.  If quiet is True, or if V is not set in the
    environment, eat its stdout and stderr by default (we'll print
    both to stderr on any failure though).

    If V is set and we're not forced to be quiet, just let stdout
    and stderr flow through as usual.  The name V is from the
    standard Linux kernel build ("V=1 make" => print everything).

    (We use quiet=True for build environment test cleanup steps;
    the tests themselves use use cmd_success() to check for failures.)
    """
    if not quiet:
        quiet = os.getenv('V') is None

    kwargs = {'universal_newlines': True}
    if quiet:
        kwargs['stdout'] = subprocess.PIPE
        kwargs['stderr'] = subprocess.STDOUT
    if shell:
        proc = subprocess.Popen(cmd, shell=True, **kwargs)
    else:
        proc = subprocess.Popen(shlex.split(cmd), **kwargs)

    # There is never any stderr output here - either it went straight
    # to os.STDERR_FILENO, or it went to the pipe for stdout.
    out, _ = proc.communicate()

    if proc.returncode:
        # We only have output if we ran in quiet mode.
        if quiet:
            print('Log:\n', out, file=sys.stderr)
        print('Error has occured running command: %s' % cmd, file=sys.stderr)
        sys.exit(proc.returncode)

    return out


BESS_DIR = os.path.dirname(os.path.abspath(__file__))