#! /usr/bin/env python

"""repeat <shell-command>

This simple program repeatedly (at 1-second intervals) executes the

shell command given on the command line and displays the output (or as

much of it as fits on the screen).  It uses curses to paint each new

output on top of the old output, so that if nothing changes, the

screen doesn't change.  This is handy to watch for changes in e.g. a

directory or process listing.

To end, hit Control-C.

"""

# Author: Guido van Rossum

# Disclaimer: there's a Linux program named 'watch' that does the same

# thing.  Honestly, I didn't know of its existence when I wrote this!

# To do: add features until it has the same functionality as watch(1);

# then compare code size and development time.

import os

import sys

import time

import curses

def main():

    if not sys.argv[1:]:

        print __doc__

        sys.exit(0)

    cmd = " ".join(sys.argv[1:])

    p = os.popen(cmd, "r")

    text = p.read()

    sts = p.close()

    if sts:

        print >>sys.stderr, "Exit code:", sts

        sys.exit(sts)

    w = curses.initscr()

    try:

        while True:

            w.erase()

            try:

                w.addstr(text)

            except curses.error:

                pass

            w.refresh()

            time.sleep(1)

            p = os.popen(cmd, "r")

            text = p.read()

            sts = p.close()

            if sts:

                print >>sys.stderr, "Exit code:", sts

                sys.exit(sts)

    finally:

        curses.endwin()

main()