A simple tool to track CPU usage of given process

tukan.py

"""
A simple process to measure CPU usage of a process during specified time
Requires at least Linux 2.6.

Care with measurement on tickless kernels!
"""
from __future__ import division
import sys, time

if len(sys.argv) != 4:
    sys.stderr.write('''Proper usage: 
python tukan.py <PID> <DELAY> <TIMES>
<PID>: PID of process to monitor
<DELAY>: (float) amount of seconds of polling interval
<TIMES>: amount of times to poll

Output is dumped on stdout. Each line is a float, percentage
of single processor usage without the percent sign
''')
    sys.exit()

def get_params(pid):
    """Returns a tuple:
    (utime+stime for PID, time_total for system)"""
    with open('/proc/%s/stat' % (pid, ), 'r') as fx:
        line = fx.read().split(' ')
        ptime = int(line[13]) + int(line[14])
    with open('/proc/stat', 'r') as fx:
        linea = map(int, fx.readline().split(' ')[2:])
        total_jiffies = sum(linea)
    return (ptime, total_jiffies)

pid, delay, times = int(sys.argv[1]), float(sys.argv[2]), int(sys.argv[3])

try:
    utime, jiffs = get_params(pid)
except IOError:
    sys.stderr.write('Error: %s does not exist\n' % (pid, ))
    sys.exit()

# Let's roll
for i in xrange(0, times):
    time.sleep(delay)

    try:
        nutime, njiffs = get_params(pid)
    except IOError:
        sys.stderr.write('Error: %s does not exist anymore\n' % (pid, ))
        sys.exit()

    cpu_usage = 100 * (nutime - utime) / (njiffs - jiffs)
    sys.stdout.write('%.2f\n' % (cpu_usage, ))
    utime = nutime
    jiffs = njiffs