C SYNOPSIS

#include <pcp/pmapi.h>

int pmGetChildren(const char *name, char ***offspring)
int pmRequestNamesOfChildren(int ctx, const char *name, int wantstatus)
int pmReceiveNamesOfChildren(int ctx, char ***offspring, int **status)

cc ... -lpcp

DESCRIPTION

Given a fully qualified pathname to a node in the current Performance Metrics Name Space (PMNS), as identified by name, pmGetChildren returns via offspring a list of the relative names of all of the immediate descendent nodes of name in the current PMNS.

As a special case, if name is an empty string (i.e.""), the immediate descendents of the root node in the PMNS will be returned.

Normally, pmGetChildren will return the number of descendent names discovered, else a value less than zero for an error. The value zero indicates that name is a valid metric name, i.e. is associated with a leaf node in the PMNS.

The resulting list of pointers offspring and the values (the relative names) that the pointers reference will have been allocated by pmGetChildren with a single call to malloc(3C), and it is the responsibility of the pmGetChildren caller to free(offspring) to release the space when it is no longer required.

When an error occurs, or name is a leaf node (i.e. the result of pmGetChildren is less than one), offspring is undefined (no space will have been allocated, and so calling free(3C) is a singularly bad idea).

pmRequestNamesOfChildren and pmReceiveNamesOfChildren are used by applications which must communicate with the PMCD asynchronously. These functions take explict context handle ctx which must refer to a host context (i.e. created by passing PM_CONTEXT_HOST to pmNewContext). pmRequestNamesOfChildren sends request to PMCD to enumerate names of the children of PMNS node and returns without waiting for the response, pmReceiveNamesOfChildren reads reply from PMCD. It is the responsibility of the application to make sure the data are ready before calling pmReceiveNamesOfChildren to avoid blocking.

If in the call to pmRequestNamesOfChildren wantstatus was set to non-zero value then pmReceiveNamesOfChildren will return the status of each child via status. The status will refer to either a leaf node (with value PMNS_LEAF_STATUS) or a non-leaf node (with value PMNS_NONLEAF_STATUS), otherwise the status is undefined and should not be referenced.

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 configuration file, as described in pcp.conf(4). Values for these variables may be obtained programatically using the pmGetConfig(3) function.

DIAGNOSTICS

PM_ERR_NOPMNS

Failed to access a PMNS for operation. Note that if the application hasn't a priori called pmLoadNameSpace(3) and wants to use the distributed PMNS, then a call to pmGetChildren must be made inside a current context.

PM_ERR_NAME

The pathname name is not valid in the current PMNS

PM_ERR_*

Other diagnostics are for protocol failures when accessing the distributed PMNS.

PM_ERR_CTXBUSY

Context is currently in use by another asynchronous call.