clock-overlay

#!/usr/bin/python2

import sys, os
from time import strftime
from time import sleep
from signal import signal, SIGALRM, setitimer, ITIMER_REAL
from errno import EINTR

format_escapes = {
	r'\e': '\x1b',
	r'\t': '\t',
	r'\n': '\x1b[B\x1b[G',
	r'\\': '\\'
}

CLEAR_NEXT_LINE = False # true to clear the line below the output as well

def main(progname, _time_format='\e[1;34m%X\e[m'):
	global time_format
	time_format = replace_all(_time_format, format_escapes)
	signal(SIGALRM, on_alarm)
	setitimer(ITIMER_REAL, 1, 1)
	patrick()

def on_alarm(signum, frame):
	clear_next_s = "\x1b[B\x1b[2K" if CLEAR_NEXT_LINE else ''
	s = "\x1b[s\x1b[H\x1b[2K" + strftime(time_format) + clear_next_s + "\x1b[u"
	while s:
		n = os.write(sys.stdout.fileno(), s)
		s = s[n:]

def patrick():
	c = None
	while 1:
		try:
			n = 0
			c = sys.stdin.read(1) if not c else c
			if not c:
				break
			n = os.write(sys.stdout.fileno(), c)
		except (OSError, IOError), ex:
			if ex.errno != EINTR:
				raise
		if n: c = None

def replace_all(s, replacements):
	for item in replacements.items():
		s = s.replace(*item)
	return s

if __name__=='__main__':
	sys.exit(main(*sys.argv))