psutil

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#!/usr/bin/env python3
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# Copyright (c) 2009, Giampaolo Rodola'. All rights reserved.
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# Use of this source code is governed by a BSD-style license that can be
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# found in the LICENSE file.
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"""Similar to 'ps aux --forest' on Linux, prints the process list
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as a tree structure.
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$ python3 scripts/pstree.py
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0 ?
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|- 1 init
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| |- 289 cgmanager
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| |- 616 upstart-socket-bridge
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| |- 628 rpcbind
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| |- 892 upstart-file-bridge
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| |- 907 dbus-daemon
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| |- 978 avahi-daemon
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| | `_ 979 avahi-daemon
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| |- 987 NetworkManager
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| | |- 2242 dnsmasq
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| | `_ 10699 dhclient
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| |- 993 polkitd
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| |- 1061 getty
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| |- 1066 su
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| | `_ 1190 salt-minion...
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...
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"""
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from __future__ import print_function
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import collections
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import sys
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import psutil
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def print_tree(parent, tree, indent=''):
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    try:
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        name = psutil.Process(parent).name()
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    except psutil.Error:
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        name = "?"
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    print(parent, name)
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    if parent not in tree:
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        return
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    children = tree[parent][:-1]
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    for child in children:
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        sys.stdout.write(indent + "|- ")
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        print_tree(child, tree, indent + "| ")
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    child = tree[parent][-1]
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    sys.stdout.write(indent + "`_ ")
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    print_tree(child, tree, indent + "  ")
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def main():
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    # construct a dict where 'values' are all the processes
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    # having 'key' as their parent
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    tree = collections.defaultdict(list)
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    for p in psutil.process_iter():
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        try:
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            tree[p.ppid()].append(p.pid)
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        except (psutil.NoSuchProcess, psutil.ZombieProcess):
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            pass
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    # on systems supporting PID 0, PID 0's parent is usually 0
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    if 0 in tree and 0 in tree[0]:
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        tree[0].remove(0)
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    print_tree(min(tree), tree)
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if __name__ == '__main__':
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    main()
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