1 #! /usr/bin/env python

     2 

     3 """repeat <shell-command>

     4 

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

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

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

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

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

    10 directory or process listing.

    11 

    12 To end, hit Control-C.

    13 """

    14 

    15 # Author: Guido van Rossum

    16 

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

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

    19 

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

    21 # then compare code size and development time.

    22 

    23 import os

    24 import sys

    25 import time

    26 import curses

    27 

    28 def main():

    29     if not sys.argv[1:]:

    30         print __doc__

    31         sys.exit(0)

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

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

    34     text = p.read()

    35     sts = p.close()

    36     if sts:

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

    38         sys.exit(sts)

    39     w = curses.initscr()

    40     try:

    41         while True:

    42             w.erase()

    43             try:

    44                 w.addstr(text)

    45             except curses.error:

    46                 pass

    47             w.refresh()

    48             time.sleep(1)

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

    50             text = p.read()

    51             sts = p.close()

    52             if sts:

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

    54                 sys.exit(sts)

    55     finally:

    56         curses.endwin()

    57 

    58 main()