ETA from external programs

howlong.py

"""Estimate Time until completion of a process.
Usage: <statusprog> | howlong.py <n>

<statusprog> is a program that writes a line to stdout from time to time.
The line is the number of items completed so far.

<n> is the total number of items to complete.

Example:
for((i=0;i<20;i++)); do echo $i; sleep 1; done | python howlong.py 20

Author: Johannes Buchner (C) 2013
"""

import sys
import progressbar

if len(sys.argv) < 2:
	sys.stderr.write(__doc__)
	sys.exit(-1)

n = int(sys.argv[1])
k = int(sys.stdin.readline())
m = n - k

print 'starting with {} of {} done. {} left'.format(k, n, m)

if m > 0:
	pbar = progressbar.ProgressBar(
		widgets=[progressbar.Percentage(), progressbar.Counter('%5d'),
		progressbar.Bar(), progressbar.ETA()],
		maxval=m).start()

	while True:
		l = sys.stdin.readline()
		if l == '': break
		l = int(l)
		pbar.update(l - k)
		if l == m:
			break

	pbar.finish()