Script to track user login/logout using UTMP

utmp_track.py

# -*- coding: utf-8 -*-
import utmp
import tabulate

from warnings import warn


def time_str(dt):
    """Convert datetime object to date-time string."""
    return dt.strftime('%Y/%m/%d %H:%M:%S')

state = None
entries = [['user', 'login', 'logout', 'hours']]
with open('wtmp', 'rb') as fd:
    buf = fd.read()
    for entry in utmp.read(buf):
        if entry.line == ':0':
            if state is None:
                if entry.user:
                    state = 'out'
                else:
                    continue
            if state == 'in':
                if entry.user:
                    warn('double-login detected (user %s->%s)'
                         % (entries[-1][0], entry.user,))
                else:
                    entries[-1] += [entry.time]
                    state = 'out'
            else:
                assert state == 'out'
                if not entry.user:
                    warn('logout detected without login')
                else:
                    entries.append([entry.user, entry.time])
                    state = 'in'
if len(entries[-1]) != 4:  # didn't finish (will usually be the case)
    assert state == 'in'
    entries.pop(-1)

# Do some nice formatting
for entry in entries[1:]:
    entry.append('%0.3f' % ((entry[2] - entry[1]).total_seconds() / 3600.))
    entry[1] = time_str(entry[1])
    entry[2] = time_str(entry[2])

table = tabulate.tabulate(entries, 'firstrow')
print(table)