Mini Shell

#!/opt/imh-python/bin/python3
"""Calculate and sort users by memory usage"""

import collections
import argparse
import subprocess
import tabulate


def parse_args():
    """Parse commandline arguments"""
    parser = argparse.ArgumentParser(
        description="""{}
RSS: Resident Set Size is memory actually in use by a process
VSZ: Virtual Set Size is a memory size assigned to a process during the
initial execution but not necessarily in use""".format(
            __doc__
        ),
        formatter_class=argparse.RawTextHelpFormatter,
    )
    parser.add_argument(
        '-n', '--num', type=int, default=15, help='number of users to show'
    )
    parser.add_argument(
        '-s',
        '--sort',
        choices=['vsz', 'rss', 'v', 'r'],
        default='rss',
        help='memory column to short by',
    )
    return parser.parse_args()


def main():
    """call parse_args, collect data from ps, sort, and print"""
    args = parse_args()
    cmd = ['ps', 'haxo', 'user,rss,vsz']
    ps_out = subprocess.run(
        cmd, text=True, stdout=subprocess.PIPE, check=False
    ).stdout
    mem = collections.defaultdict(lambda: [0, 0])

    for line in ps_out.splitlines():
        user, rss, vsz = line.split()
        mem[user][0] += int(rss)
        mem[user][1] += int(vsz)

    out = []
    for user, datum in list(mem.items()):
        out.append([user, datum[0], datum[1]])

    if args.sort.startswith('r'):
        out = sorted(out, key=lambda x: x[1])
    else:
        out = sorted(out, key=lambda x: x[2])

    print(tabulate.tabulate(out[-args.num :], headers=['user', 'rss', 'vsz']))


if __name__ == '__main__':
    main()