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      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()
     59