Splitting out the output of ps using Python

Question

On Linux, the command ps aux outputs a list of processes with multiple columns for each stat. e.g.

USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START          


        

Answer 1

Check out the python.psutils package.

psutil.process_iter returns a generator which you can use to iterate over all processes. p.cmdline is a list of each Process object's cmdline arguments, separated just the way you want.

You can create a dictionary of pids vs (pid,cmdline,path) with just one line and then use it anyway you want.

pid_dict = dict([(p.pid, dict([('pid',p.pid), ('cmdline',p.cmdline), ('path',p.path)]))
                 for p in psutil.process_iter()]))

Answer 2

The maxsplit optional argument to the split method might help you:

sep.split.(row, maxsplit=42)

Answer 3

Here's a nice routine and usage to get you going:

def getProcessData():
    ps = subprocess.Popen(['ps', 'aux'], stdout=subprocess.PIPE).communicate()[0]
    processes = ps.split('\n')
    # this specifies the number of splits, so the splitted lines
    # will have (nfields+1) elements
    nfields = len(processes[0].split()) - 1
    retval = []
    for row in processes[1:]:
        retval.append(row.split(None, nfields))
    return retval

wantpid = int(contents[0])
pstats = getProcessData()
for ps in pstats:
    if (not len(ps) >= 1): continue
    if (int(ps[1]) == wantpid):
        print "process data:"
        print "USER              PID       %CPU        %MEM       VSZ        RSS        TTY       STAT      START TIME      COMMAND"
        print "%-10.10s %10.10s %10.10s %10.10s %10.10s %10.10s %10.10s %10.10s %10.10s  %s" % (ps[0], ps[1], ps[2], ps[3], ps[4], ps[5], ps[6], ps[7], ps[8], ps[9])

Answer 4

Use the second parameter to split which specifies the maximum number of fields to split the string into. I guess you can find the number by counting the number of fields in the first line, i.e. the column titles.

ps = subprocess.Popen(['ps', 'aux'], stdout=subprocess.PIPE).communicate()[0]
processes = ps.split('\n')
# this specifies the number of splits, so the splitted lines
# will have (nfields+1) elements
nfields = len(processes[0].split()) - 1
for row in processes[1:]:
    print row.split(None, nfields)

Answer 5

Why don't you use PSI instead? PSI provides process information on Linux and other Unix variants.

import psi.process
for p in psi.process.ProcessTable().values(): …