I have rewrited my code as follow, but it still not working. import os, sys
pid = os.fork() if pid == 0: os.execvp("du",("du","-shc","/usr/share")) else: while 1: try: os.kill(pid,0) sys.stdout.write('running') sys.stdout.flush() sys.stdout.write('\b\b\b\b\b\b\b') except OSError: print "child ended" -- http://mail.python.org/mailman/listinfo/python-list