pidtree: Faster by running ps once.

pidtree/pidtree

@@ -0,0 +1,92 @@
+#!/bin/bash
+
+: <<=cut
+=pod
+
+=head1 NAME
+
+pidtree - List children of process ID
+
+
+=head1 SYNOPSIS
+
+B<pidtree> I<pid> [I<pids>]
+
+
+=head1 DESCRIPTION
+
+B<pidtree> lists the process IDs of the (grand*)children of the I<pid>.
+
+=head1 EXAMPLES
+
+Show the tree for all processes on the system:
+
+  pidtree 1
+
+Show the tree for this process:
+
+  pidtree $$
+
+Kill process and all (grand*)children:
+
+  pidtree 12345 | xargs kill
+
+
+=head1 AUTHOR
+
+Copyright (C) 2020 Ole Tange,
+http://ole.tange.dk and Free Software Foundation, Inc.
+
+
+=head1 LICENSE
+
+Copyright (C) 2012 Free Software Foundation, Inc.
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3 of the License, or
+at your option any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+
+=head1 DEPENDENCIES
+
+B<pidtree> uses B<ps>.
+
+
+=head1 SEE ALSO
+
+B<ps>, B<pstree>.
+
+
+=cut
+
+_pidtree() {
+    declare -A children
+    # Make table pid => child pids
+    # This way we only run 'ps' once
+    while read pid parent ; do
+        children[$parent]+=" $pid"
+    done < <(ps -e -o pid,ppid)
+
+    __pidtree() {
+	# Indent pid with spaces ($1)
+        echo "$1$2"
+        for child in ${children["$2"]} ; do
+            __pidtree " $1" "$child"
+        done
+    }
+
+    for pid in "$@" ; do
+        __pidtree '' "$pid"
+    done
+}
+
+_pidtree "$@"