pmdabash(1) — Linux manual page


PMDABASH(1)              General Commands Manual             PMDABASH(1)

NAME         top

       pmdabash - Bourne-Again SHell trace performance metrics domain

SYNOPSIS         top

       $PCP_PMDAS_DIR/bash/pmdabash [-C] [-d domain] [-l logfile] [-I
       interval] [-t timeout] [-U username] configfile

DESCRIPTION         top

       pmdabash is an experimental Performance Metrics Domain Agent
       (PMDA) which exports "xtrace" events from a traced bash(1)
       process.  This includes the command execution information that
       would usually be sent to standard error with the set -x option to
       the shell.

       Event metrics are exported showing each command executed, the
       function name and line number in the script, and a timestamp.
       Additionally, the process identifier for the shell and its parent
       process are exported.

       This requires bash version 4 or later.

       A brief description of the pmdabash command line options follows:

       -d   It is absolutely crucial that the performance metrics domain
            number specified here is unique and consistent.  That is,
            domain should be different for every PMDA on the one host,
            and the same domain number should be used for the same PMDA
            on all hosts.

       -l   Location of the log file.  By default, a log file named
            bash.log is written in the current directory of pmcd(1) when
            pmdabash is started, i.e.  $PCP_LOG_DIR/pmcd.  If the log
            file cannot be created or is not writable, output is written
            to the standard error instead.

       -s   Amount of time (in seconds) between subsequent evaluations
            of the shell trace file descriptor(s).  The default is 2

       -m   Maximum amount of memory to be allowed for each event queue
            (one per traced process).  The default is 2 megabytes.

       -U   User account under which to run the agent.  The default is
            the unprivileged "pcp" account in current versions of PCP,
            but in older versions the superuser account ("root") was
            used by default.

INSTALLATION         top

       In order for a host to export the names, help text and values for
       the bash performance metrics, do the following as root:

            # cd $PCP_PMDAS_DIR/bash
            # ./Install

       As soon as an instrumented shell script (see INSTRUMENTATION
       selection below) is run, with tracing enabled, new metric values
       will appear - no further setup of the agent is required.

       If you want to undo the installation, do the following as root:

            # cd $PCP_PMDAS_DIR/bash
            # ./Remove

       pmdabash is launched by pmcd(1) and should never be executed
       directly.  The Install and Remove scripts notify pmcd(1) when the
       agent is installed or removed.


       In order to allow the flow of event data between a bash(1) script
       and pmdabash, the script should take the following actions:

            source $PCP_DIR/etc/pcp.env
            source $PCP_SHARE_DIR/lib/

            pcp_trace on $@       # enable tracing
            echo "awoke, $count"

            pcp_trace off         # disable tracing

       The tracing can be enabled and disabled any number of times by
       the script.  On successful installation of the agent, several
       metrics will be available:

            $ pminfo bash

       When an instrumented script is running, the generation of event
       records can be verified using the pmevent(1) command, as follows:

            $ pmevent -t 1 -x '' bash.xtrace.records
            host:      localhost
            samples:   all
            bash.xtrace.records["4538 ./ 1 2 3"]: 5 event records
              10:00:05.000 --- event record [0] flags 0x19 (point,id,parent) ---
                bash.xtrace.parameters.parent 4432
                bash.xtrace.parameters.lineno 43
                bash.xtrace.parameters.command "true"
              10:00:05.000 --- event record [1] flags 0x19 (point,id,parent) ---
                bash.xtrace.parameters.parent 4432
                bash.xtrace.parameters.lineno 45
                bash.xtrace.parameters.command "((  count++  ))"
              10:00:05.000 --- event record [2] flags 0x19 (point,id,parent) ---
                bash.xtrace.parameters.parent 4432
                bash.xtrace.parameters.lineno 46
                bash.xtrace.parameters.command "echo 'awoke, 3'"
              10:00:05.000 --- event record [3] flags 0x19 (point,id,parent) ---
                bash.xtrace.parameters.parent 4432
                bash.xtrace.parameters.lineno 47
                bash.xtrace.parameters.command "tired 2"
              10:00:05.000 --- event record [4] flags 0x19 (point,id,parent) ---
                bash.xtrace.parameters.parent 4432
                bash.xtrace.parameters.lineno 38
                bash.xtrace.parameters.function "tired"
                bash.xtrace.parameters.command "sleep 2"

FILES         top

              command line options used to launch pmdabash
              default help text file for the bash metrics
              installation script for the pmdabash agent
              undo installation script for pmdabash
              default log file for error messages and other information
              from pmdabash


       Environment variables with the prefix PCP_ are used to
       parameterize the file and directory names used by PCP.  On each
       installation, the file /etc/pcp.conf contains the local values
       for these variables.  The $PCP_CONF variable may be used to
       specify an alternative configuration file, as described in

SEE ALSO         top

       bash(1), pmevent(1) and pmcd(1).

COLOPHON         top

       This page is part of the PCP (Performance Co-Pilot) project.
       Information about the project can be found at 
       ⟨⟩.  If you have a bug report for this manual
       page, send it to  This page was obtained from the
       project's upstream Git repository
       ⟨⟩ on 2023-12-22.
       (At that time, the date of the most recent commit that was found
       in the repository was 2023-12-16.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

Performance Co-Pilot               PCP                       PMDABASH(1)