pmGetOptionalConfig(3) return values for Performance Co-Pilot configuration variables

Other Alias



#include <pcp/pmapi.h>
char *pmGetConfig(const char *
char *pmGetOptionalConfig(const char *variable);

#include <pcp/impl.h>
char *__pmGetAPIConfig(const char *feature);

cc ... -lpcp


The pmGetConfig and pmGetOptionalConfig functions search for variable first in the environment and then, if not found, in the Performance Co-Pilot (PCP) configuration file and returns the string result. If variable is not already in the environment, it is added with a call to putenv(3) before returning.

The pmGetOptionalConfig function allows for failures - either from variable not being set at all, or due to the configuration file being missing. pmGetConfig is less tolerant to a missing configuration file, which it treats as a critical PCP installation failure - see the ``RETURN VALUE'' section below for further details.

The default location of the PCP configuration file is /etc/pcp.conf but this may be changed by setting PCP_CONF in the environment to a new location, as described in pcp.conf(5).

The internal __pmGetAPIConfig function reports on features of the PCP library. It can be used to query support for multi-threading, security extensions, and other features.

The pmconfig(1) utility provides command line access to both of these interfaces, and also provides a mechanism for listing all available variables and features that are valid arguments to these routines.


If variable is not found in either the environment or the PCP configuration file, or if the configuration file is inaccessible, then pmGetOptionalConfig returns NULL.

If variable is found in neither the environment nor the PCP configuration file, then pmGetConfig returns an empty string. If the PCP configuration file is not found then a fatal error message is printed and the process will exit(2) - although this sounds drastic, it is the only course of action available because the PCP configuration/installation is deemed fatally flawed.

The __pmGetAPIConfig routine returns NULL on failure to lookup the requested feature. It does not modify the environment, and returns a pointer to a static read-only string.

The value returned by all of these routines is either a static pointer or pointer into the environment, and so changing it is a bad idea.


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). Values for these variables may be obtained programmatically using the pmGetConfig(3) function.