ps-watcher(8)

📦

version 1.08 · 6 versions

1.08 · ubuntu resolute, ubuntu stonking (latest)
1.08 · ubuntu questing
1.08 · ubuntu jammy
1.08 · ubuntu noble
1.08 · debian bookworm
1.08 · debian trixie

💖 NAME 💖

okay so bestie, this is ps-watcher(8), hanging out in the User Contributed Perl Documentation corner of your man pages. And what does it do? It monitors various processes based on ps-like information. periodt. 💅

✨ SYNOPSIS ✨

ps-watcher [options...]
            ["--config"] config-file

🌸 DESCRIPTION 🌸

Periodically, it gets a list of processes via ps. More precisely, each item in the list contains the process name (just what's listed in the cmd field, not the full command and arguments) and its process id (pid). A configuration file specifies a list of Perl regular-expression patterns to match the processes against. For each match, a Perl expression specified for that pattern is evaluated. The evaluated expression can refer to variables which are set by ps and pertain to the matched process(es), for example the amount memory consumed by the process, or the total elapsed time. Some other variables are set by the program, such as the number of times the process is running. If the Perl expression for a matched pattern evaluates true, then an action can be run such as killing the program, restarting it, or mailing an alert, or running some arbitrary Perl code. 👑

Some things you might want to watch a daemon or process for:

check that it is running (hasn't died) 💀
ensure it is not running too many times 👯
isn't consuming too much memory (perhaps a memory leak), or I/O 😭

Some actions you might want to take:

restart a process 🔁
kill off rampant processes 🔪
send an alert about any of the conditions listed above 🚨

Depending on the options you specify, this program can be run as a daemon, run once (which is suitable as a cron job), or run not as a daemon but still continuously (which may be handy in testing the program or your configuration). 🦋

🎀 OPTIONS 🎀

--help — Print a usage message on standard error and exit with a return code of 100.
--doc — Extact the full documentation that you are reading now, print it and exit with a return code of 101.
--version — Print the version release on standard output and exit with a return code of 10.
--debug number — Give debugging output. The higher the number, the more the output. The default is 0 = none. 2 is the most debugging output.
[--config] configuration file — Specify configuration file. .

See "CONFIGURATION FILE FORMAT" below for information on the format of the configuration file and "EXAMPLE CONFIGURATION" for a complete example of a configuration file.

--log [log file] — Send or don't send error and debugging output to a log file. If option is given but no logfile is specified, then use STDERR. The default is no error log file. See also --syslog below.
--syslog | --nosyslog — Send or don't send error and debugging output to syslog. The default is to syslog error and debug output.
--daemon | --nodaemon — Run or don't run as a daemon.
--path search-path — Specify the executable search path used in running commands.
--ps-prog program — One can specify the command that gives ps information. By default, the command is /usr/bin/ps.
--run | --norun — do/don't run actions — go through the motions as though we were going to. This may be useful in debugging.
--sleep interval in seconds — It is expected that one might want to run ps-watcher over and over again. In such instances one can specify the amount of time between iterations with this option.

If a negative number is specified the program is run only once. 😴

🌈 CONFIGURATION FILE MODIFICATION AND SIGNAL HANDLING 🌈

Periodically ps-watcher checks to see if the configuration file that it was run against has changed. If so, the program rereads the configuration file. 🔄

More precisely, the checks are done after waking up from a slumber. If the sleep interval is long (or if you are impatient), you can probably force the program to wake up using a HUP signal. ⏰

At any time you can increase the level of debug output by sending a USR1 signal to the ps-watcher process. Similarly you can decrease the level of debug output by sending the process a USR2 signal. 📶

It is recommended that you terminate ps-watcher via an INT, TERM, or QUIT signal. 🫶

✨ CONFIGURATION FILE FORMAT ✨

okay bestie, so the config file is giving very much structured but make it readable 💅 It's a series of fully qualified filenames wrapped in square brackets, and then a bunch of parameter lines. Each parameter line is <parameter name> = <value> — no cap. Like:

# This is a comment line
; So is this.
[process-pattern1]
 parameter1 = value1
 parameter2 = value2

[process-pattern2]
 parameter1 = value3
 parameter2 = value4

Comments start with # or ; and they take effect to the end of the line. So whatever you say after those is private, bestie 🤫

This should be familiar to those who have worked with text-readible Microsoft ".INI" files. It's literally that vibe.

Note: process patterns (like process-pattern1 and process-pattern2 above) must be unique. If there are times when you may want to refer to the same process, one can be creative to make these unique. e.g. cron and [c]ron which refer to the same process even though they appear to be different.

As quoted directly from the Config::IniFiles documentation:

Multiline or multivalued fields may also be defined ala UNIX "here document" syntax: Parameter=<<EOT value/line 1 value/line 2 EOT

You may use any string you want in place of "EOT". Note that what follows the << and what appears at the end of the text must match exactly, including any trailing whitespace. So don't play with trailing spaces, bestie, it will not eat 💀

There are two special "process patterns": $PROLOG and $EPILOG, the former should appear first and the latter last. They're like the opening and closing credits of your config 🎬

You can put perl code to initialize variables here and do cleanup actions in these sections using perl-action.

A description of parameters names, their meanings and potential values follows.

💖 trigger 💖

This parameter specifies the condition on which a process action is fired. The condition is evaluated with Perl eval() and should therefore return something which is equivalent to "true" in a Perl expression.

If no trigger is given in a section, true or 1 is assumed and the action is unconditionally triggered.

Example:

# Match if httpd has not spawned enough (<4) times. NFS and databases
# daemons typically spawn child processes.  Since the program
# matches against the command names, not commands and arguments,
# something like: ps -ef | grep httpd won't match the below.
# If you want to match against the command with arguments, see
# the example with $args below.
[httpd$]
trigger = $count <= 4

🦋 occurs 🦋

This parameter specifies how many times an action should be performed on processes matching the section trigger. Acceptable values are "every", "first", "first-trigger", and "none".

Setting the occurs value to "none" causes the the trigger to be evaluated when there are no matching processes. (Yes, "the the" — I said what I said, it's in the source 💅) Although one might think "$count == 0" in the action expression would do the same thing, currently as coded this does not work.

Setting the occurs value to "first" causes the process-pattern rule to be finished after handling the first rule that matches, whether or not the trigger evaluated to true.

Setting the occurs value to "first-trigger" causes the process-pattern rule to be finished after handling the first rule that matches and the trigger evaluates to true.

If the item parameter is not specified, "first" is assumed.

Examples:

[.]
occurs = first
action = echo "You have $count processes running"

# Note in the above since there is no trigger specified,
#   occurs = first
# is the same thing as
#   occurs = first-trigger

[.?]
trigger = $vsz > 1000
occurs  = every
action  = echo "Large program $command matches $ps_pat: $vsz KB"

# Fire if /usr/sbin/syslogd is not running.
# Since the program matches against the command names, not commands and
# arguments, something like:
#   ps -ef | grep /usr/sbin/syslogd
# won't match the below.
[(/usr/sbin/)?syslogd]
occurs = none
action = /etc/init.d/syslogd start

🌸 action 🌸

This specifies the action, a command that gets run by the system shell, when the trigger condition is evaluated to be true.

Example:

action = /etc/init.d/market_loader.init restart

✨ perl-action ✨

This specifies Perl statements to be eval'd. This can be especially useful in conjunction with $PROLOG and $EPILOG sections to make tests across collections of process and do things which ps-watcher would otherwise not be able to do.

Example:

# A Perl variable initialization.
# Since ps-watcher runs as a daemon it's a good idea
# to (re)initialize variables before each run.
[$PROLOG]
  perl-action = $root_procs=0;

# Keep track of how many root processes we are running
[.*]
  perl-action = $root_procs++ if $uid == 0
  occurs  = every

# Show this count.
[$EPILOG]
  action  = echo "I counted $root_procs root processes"

🌈 EXPANDED VARIABLES IN TRIGGER/ACTION CLAUSES 🌈

Any variables defined in the program can be used in pattern or action parameters. For example, $program can be used to refer to the name of this program ps-watcher.

The following variables can be used in either the pattern or action fields.

$action — A string containing the text of the action to run.
$perl_action — A string containing the text of the perl_action to run.
$ps_pat — The Perl regular expression specified in the beginning of the section.
$command — The command that matched $ps_pat.

The Perl regular expression specified in the beginning of the section. Normally processes will not have funny characters in them. Just in case, backticks in $command are escaped.

Example:

# List processes other than emacs (which is a known pig) that use lots
# of virtual memory

[.*]
trigger = $command !~ /emacs$/ && $vsz > 10
action  = echo \"Looks like you have a big \$command program: \$vsz KB\"

$count — The number of times the pattern matched. Presumably the number of processes of this class running.
$trigger — A string containing the text of the trigger.

A list of variables specific to this program or fields commonly found in "ps" output is listed below followed by a description of the more common ones. See also "ps" for a more complete description of the meaning of the field.

uid euid ruid gid egid rgid alarm blocked bsdtime c caught
cputime drs dsiz egroup eip esp etime euser f fgid
fgroup flag flags fname fsgid fsgroup fsuid fsuser fuid fuser
group ignored intpri lim longtname m_drs m_trs maj_flt majflt
min_flt  minflt ni nice nwchan opri pagein pcpu pending pgid pgrp
pmem ppid pri rgroup rss rssize rsz ruser s sess session
sgi_p sgi_rss sgid sgroup sid sig sig_block sig_catch sig_ignore
sig_pend sigcatch sigignore sigmask stackp start start_stack start_time
stat state stime suid suser svgid svgroup svuid svuser sz time timeout
tmout tname tpgid trs trss tsiz tt tty tty4 tty8 uid_hack uname
user vsize vsz wchan

Beware though, in some situations ps can return multiple lines for a single process and we will use just one of these in the trigger. In particular, Solaris's "ps" will return a line for each LWP (light-weight process). So on Solaris, if a trigger uses variable lwp, it may or may not match depending on which single line of the multiple "ps" lines is used.

$args — The command along with its command arguments. It is possible that this is might get truncated at certain length (if ps does likewise as is the case on Solaris).
$ppid — The parent process id.
$stime — The start time of the process.
$etime — The end time of the process.
$pmem — The process memory.
$pcpu — The percent CPU utilization.
$tty — The controlling tty.
$vsz — Virtual memory size of the process

💫 OTHER THINGS IN TRIGGER CLAUSES 💫

To make testing against elapsed time easier, a function elapse2sec() has been written to parse and convert elapsed time strings in the format "dd-hh:mm:ss" and a number of seconds.

Some constants for the number of seconds in a minute, hour, or day have also been defined. These are referred to as "MINS", "HOURS", and "DAYS" respectively and they have the expected definitions:

use constant MINS   => 60;
use constant HOURS  => 60*60;
use constant DAYS   => HOURS * 24;

Here is an example of the use of elapsed2sec():

# Which processes have been running for more than 3 hours?
# Also note use of builtin-function elapsed2secs, variable $etime
# and builtin-function HOURS
[.]
  trigger = elapsed2secs('$etime') > 1*DAYS
  action  = echo "$command has been running more than 1 day ($etime)"
  occurs  = every

Please note the quotes around '$etime'.

🎀 EXAMPLE CONFIGURATION 🎀

# Comments start with # or ; and go to the end of the line.

# The format for each entry is in Microsoft .INI form:
# [process-pattern]
# trigger = perl-expression
# action  = program-and-arguments-to-run

[httpd$]
  trigger = $count < 4
  action  = echo "$trigger fired -- You have $count httpd sessions."

[.]
trigger = $vsz > 10
action  = echo "Looks like you have a big $command program: $vsz KB"

# Unfortunately we have use a different pattern below. (Here we use
# ".?" instead of ".".) In effect the the two patterns mean
# test every process.
[.?]
  trigger = elapsed2secs('$etime') > 2*MINS && $pcpu > 40
  occurs  = every
  action  = <<EOT
   echo "$command used $pcpu% CPU for the last $etime seconds" | /bin/mail root
   kill -TERM $pid
EOT

# Scripts don't show as the script name as the command name on some
# operating systems.  Rather the name of the interpreter is listed
# (e.g. bash or perl) Here's how you can match against a script.
# BSD/OS is an exception: it does give the script name rather than
# the interpreter name.
[/usr/bin/perl]
  trigger = \$args !~ /ps-watcher/
  occurs  = every
  action  = echo "***found perl program ${pid}:\n $args"

🌸 Using `$PROLOG` for getting non-ps information 🌸

Okay bestie, here's the tea ☕ — sometimes you wanna use ps-watcher to do something that plain old ps literally cannot do. Like, checking if a port is active?? Not a ps thing, never was. So we bring in lsof to peek at port 3333, and we use the $PROLOG to make sure it actually runs. Iconic teamwork 💅

[$PROLOG]
  occurs  = first
  trigger = { \$x=`lsof -i :3333 >/dev/null 2>&1`; \$? >> 8 }
  action  = <<EOT
  put-your-favorite-command-here arg1 arg2 ...
EOT

Like yes, put your fave command in there, she's ready 🎀

🔒 SECURITY CONSIDERATIONS 🔒

Okay so real talk, no cap: any daemon this flexible is a security risk. Periodt. 💀 The configuration file lets you run arbitrary commands. So if this daemon is running as root and the config file isn't protected from modification?? A bad person could literally have their own programs run as root. Not the vibe. Not it at all. 😭

Good news though: there is nothing in the ps command or in ps-watcher that requires you to run this daemon as root. Zero. None. 🫶

So, same as with all daemons: take the usual security precautions that any careful sysadmin/maintainer of a computer would take. If you can run any daemon as an unprivileged user (or with no privileges at all), do it! If you can't, then set the permissions on the configuration file and the directory it lives in. Lock it down bestie 🔐

This program can also run chrooted, and there's a --path option available which you can use to set the executable search path. Every command used by ps-watcher is fully qualified, and the author generally gives a full execution path in their configuration file, so consider using the option --path=''.

Commands that need to be run as root? You can run those via sudo. The author often runs process accounting which tracks all commands run. Tripwire may be useful to track changed configuration files. Very detective, very slay 🕵️‍♀️✨

🩺 TROUBLESHOOTING 🩺

To debug a configuration file, these options are useful:

ps-watcher --log --nodaemon --sleep -1 --debug 2 *config-file*

And for EVEN MORE information and control, try running the above under the perl debugger, like:

perl -d ps-watcher --log --nodaemon --sleep -1 --debug 2 *config-file*

Obsessed with a good debugger moment honestly 🐛💜

🐛 BUGS 🐛

Okay so, some of these aren't so much a bug in ps-watcher as they are a challenge to getting ps-watcher to do what you want it to do. It's giving "it's not me, it's the situation" 💀

One common problem people run into is understanding exactly what the process variables mean. The manual page ps(1) should be of help, but the author has found some of the descriptions either a bit vague or just plain lacking. 🙈

Sometimes you'll see this error message when debug tracing is turned on:

** debug ** Something wrong getting ps variables

This just means the process died between the time ps-watcher first saw the existence of the process and the time that it queried variables. RIP to that process, she simply left the chat 🪦✨

👀 SEE ALSO 👀

💖 AUTHOR 💖

Rocky Bernstein (rocky@gnu.org)

📜 COPYRIGHT 📜

Copyright (C) 2000, 2002, 2003, 2004, 2005, 2006, 2008
Rocky Bernstein, email: rocky@gnu.org.
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 2 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, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

And that's a wrap bestie!! 🎀✨ This whole thing is ps-watcher(8), from the Perl v5.40.1 era, dated 2025-09-07 — go forth and watch those processes, you absolute main character 👑💅🦋

📦 where this page comes from

ubuntu resolute: ps-watcher 1.08-12 · GPL-2.0-or-later
ubuntu stonking: ps-watcher 1.08-12 · GPL-2.0-or-later
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash on 2026-11-03: a language model's rewrite of the original, under its terms

ps-watcher(8)

💖 NAME 💖

✨ SYNOPSIS ✨

🌸 DESCRIPTION 🌸

🎀 OPTIONS 🎀

🌈 CONFIGURATION FILE MODIFICATION AND SIGNAL HANDLING 🌈

✨ CONFIGURATION FILE FORMAT ✨

💖 trigger 💖

🦋 occurs 🦋

🌸 action 🌸

✨ perl-action ✨

🌈 EXPANDED VARIABLES IN TRIGGER/ACTION CLAUSES 🌈

💫 OTHER THINGS IN TRIGGER CLAUSES 💫

🎀 EXAMPLE CONFIGURATION 🎀

🌸 Using $PROLOG for getting non-ps information 🌸

🔒 SECURITY CONSIDERATIONS 🔒

🩺 TROUBLESHOOTING 🩺

🐛 BUGS 🐛

👀 SEE ALSO 👀

💖 AUTHOR 💖

📜 COPYRIGHT 📜

🌸 Using `$PROLOG` for getting non-ps information 🌸