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NAME | SYNOPSIS | DESCRIPTION | INSTALLATION | INSTRUMENTATION | FILES | PCP ENVIRONMENT | DEBUGGING OPTIONS | SEE ALSO | COLOPHON |
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PMDABASH(1) General Commands Manual PMDABASH(1)
pmdabash - Bourne-Again SHell trace performance metrics domain
agent
$PCP_PMDAS_DIR/bash/pmdabash [-C] [-D debug] [-d domain] [-l
logfile] [-I interval] [-t timeout] [-U username] configfile
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
seconds.
-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.
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:
#!/bin/sh
source $PCP_DIR/etc/pcp.env
source $PCP_SHARE_DIR/lib/bashproc.sh
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
bash.xtrace.numclients
bash.xtrace.maxmem
bash.xtrace.queuemem
bash.xtrace.count
bash.xtrace.records
bash.xtrace.parameters.pid
bash.xtrace.parameters.parent
bash.xtrace.parameters.lineno
bash.xtrace.parameters.function
bash.xtrace.parameters.command
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 ./test-trace.sh 1 2 3"]: 5 event records
10:00:05.000 --- event record [0] flags 0x19 (point,id,parent) ---
bash.xtrace.parameters.pid 4538
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.pid 4538
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.pid 4538
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.pid 4538
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.pid 4538
bash.xtrace.parameters.parent 4432
bash.xtrace.parameters.lineno 38
bash.xtrace.parameters.function "tired"
bash.xtrace.parameters.command "sleep 2"
$PCP_PMCDCONF_PATH
command line options used to launch pmdabash
$PCP_PMDAS_DIR/bash/help
default help text file for the bash metrics
$PCP_PMDAS_DIR/bash/Install
installation script for the pmdabash agent
$PCP_PMDAS_DIR/bash/Remove
undo installation script for pmdabash
$PCP_LOG_DIR/pmcd/bash.log
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 pcp.conf(5).
The -D or --debug option enables the output of additional
diagnostics on stderr to help triage problems, although the
information is sometimes cryptic and primarily intended to provide
guidance for developers rather end-users. debug is a comma
separated list of debugging options; use pmdbg(1) with the -l
option to obtain a list of the available debugging options and
their meaning.
Debugging options specific to pmdabash are as follows:
┌────────┬───────────────────────────────────────┐
│ Option │ Description │
├────────┼───────────────────────────────────────┤
│ appl0 │ verbose logging of events of interest │
└────────┴───────────────────────────────────────┘
bash(1), pmevent(1) and pmcd(1).
This page is part of the PCP (Performance Co-Pilot) project.
Information about the project can be found at
⟨http://www.pcp.io/⟩. If you have a bug report for this manual
page, send it to pcp@groups.io. This page was obtained from the
project's upstream Git repository
⟨https://github.com/performancecopilot/pcp.git⟩ on 2025-08-11.
(At that time, the date of the most recent commit that was found
in the repository was 2025-08-11.) 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
man-pages@man7.org
Performance Co-Pilot PCP PMDABASH(1)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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