PMDABASH(1)						      General Commands Manual						       PMDABASH(1)

NAME

       pmdabash - Bourne-Again SHell trace performance metrics domain agent

SYNOPSIS

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

DESCRIPTION

       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.

INSTALLATION

       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.

INSTRUMENTATION

       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.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"

FILES

       $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

PCP ENVIRONMENT

       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 configura-
       tion file, as described in pcp.conf(5).

SEE ALSO

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

Performance Co-Pilot							PCP							       PMDABASH(1)