PMGETARCHIVEEND(3)

NAME
pmGetArchiveEnd - locate logical end of file for a set of archives

C SYNOPSIS
#include <pcp/pmapi.h>

int pmGetArchiveEnd(struct timespec *tp);

cc ... -lpcp

DESCRIPTION
Assuming the current PMAPI context is associated with a set of archives, pmGetArchiveEnd will attempt to find the logical end of file (after the last complete record in the set of archives), and return the last recorded timestamp via tp. This timestamp may be passed to pmSetMode(3) to reliably position the context at the last valid archive record, e.g. in preparation for subsequent reading in reverse chronological order.

For archives that are not concurrently being written, the physical end of file and the logical end of file are co-incident. However if an archive is being written by pmlogger(1) at the same time an application is trying to read the archive, the logical end of file may be before the physical end of file due to write buffering that is not aligned with the logical record boundaries.

pmGetArchiveEnd return an error less than zero if the context is neither valid, nor associated with a set of archives, or the set of archives is seriously corrupted. Otherwise, the return value is 0 if there has been no change of state since the last call, or 1 if the logical end of file has advanced since the last call.

In the absence of an error, the result returned via tp is well-defined.

Both pmGetArchiveEnd preserve the positioning state of the archive file prior to this function call.

COMPATIBILITY
Prior to PCP 7.0 and libpcp.so.4 the tp argument was a struct timeval. To support PMAPI transition, the old interface and semantics can be used if applications are linked with libpcp.so.3 or recompiled with -DPMAPI_VERSION=2.

For a time in PCP 6.x there was a routine with the same semantics as the current pmGetArchiveEnd called pmGetHighResArchiveEnd, although this is now deprecated and compile-time support for pmGetHighResArchiveEnd will be removed in a future release.

DIAGNOSTICS

PM_ERR_NOCONTEXT
    the current PMAPI context is either invalid, or not associated with a set of archives

PM_ERR_LOGREC
    the set of archives is sufficiently damaged, that not a single valid record can be found

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

SEE ALSO
PMAPI(3), pmFetch(3), pmFetchArchive(3), pmGetArchiveLabel(3), pmGetConfig(3), pmSetMode(3), pcp.conf(5) and pcp.env(5).