指定されたコマンドを実行して、その出力にラベルを付与して出力するコマンド

label.py

#!/usr/bin/python
from argparse import ArgumentParser, REMAINDER
import os
import select
from subprocess import Popen, PIPE
import sys

def read_and_write(poll, rem, files, label):
    for fd, _ in poll.poll():
        buf = os.read(fd, 1024)
        if len(buf) > 0:
            lines = buf.split("\n")
            lines[0] = rem[fd] + lines[0]
            for line in lines[:-1]:
                files[fd].write("[{}] {}\n".format(label, line))
            rem[fd] = lines[-1]
        else:
            if len(rem[fd]) > 0:
                files[fd].write("[{}] {}".format(label, rem[fd]))
            poll.unregister(fd)
            del rem[fd]
            del files[fd]

def main():
    parser = ArgumentParser(usage="label LABEL -- COMMAND...",
                            description="add LABEL to the output of COMMAND.")
    parser.add_argument("label", metavar="LABEL",
                        help="a label added to each line of the output.")
    parser.add_argument("command", metavar="COMMAND", nargs=REMAINDER,
                        help="a command to run.")
    parser.print_usage = parser.print_help
    args = parser.parse_args()

    p = Popen(args.command, stdin=sys.stdin, stdout=PIPE, stderr=PIPE)

    poll = select.poll()
    poll.register(p.stdout)
    poll.register(p.stderr)

    rem = {p.stdout.fileno(): "", p.stderr.fileno(): ""}
    files = {p.stdout.fileno(): sys.stdout, p.stderr.fileno(): sys.stderr}
    while rem:
        read_and_write(poll, rem, files, args.label)
    p.wait()
    sys.exit(p.returncode)

if __name__ == "__main__":
    main()