Demo/curses/repeat.py

   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()