NAME

       pmGetHostName,  pmGetContextHostName,  pmGetContextHostName_r  -  return  the  hostname associated with a
       Performance Co-Pilot context

C SYNOPSIS

       #include <pcp/pmapi.h>

       int pmGetHostName(int id, char *buf, int buflen);
       const char *pmGetContextHostName(int id);
       char *pmGetContextHostName_r(int id, char *buf, int buflen);

       cc ... -lpcp

DESCRIPTION

       Given a valid PCP context identifier previously created  with  pmNewContext(3)  or  pmDupContext(3),  the
       pmGetContextHostName  function returns the hostname associated with id.  The pmGetContextHostName_r func‐
       tion does the same, but stores the result in a user-supplied buffer buf of length  buflen,  which  should
       have room for at least MAXHOSTNAMELEN bytes.  The pmGetHostName function behaves similarly again, but re‐
       turns a status code to indicate success or failure.

       If  the  context id is associated with an archive source of data, the hostname returned is extracted from
       the archive label using pmGetArchiveLabel(3).

       For live contexts, an attempt will first be made to retrieve the hostname from the PCP  collector  system
       using  pmFetch(3)  with  the  pmcd.hostname metric.  This allows client tools using this interface to re‐
       trieve an accurate host identifier even in the presence of port forwarding and tunnelled connections.

       Should this not succeed, then a fallback method is used.  For local contexts - with local meaning any  of
       DSO,  ``localhost'' or Unix domain socket connection - a hostname will be sought via gethostname(3).  For
       other contexts, the hostname extracted from the initial context host specification will be used.

RETURN VALUE

       If id is not a valid PCP context identifier, the returned hostname is a zero length string.

       On failure, the return code of pmGetHostName is a negative PMAPI error code which  can  be  processed  by
       pmErrStr_r(3) for diagnostics relating to the failure to obtain the context hostname.

NOTES

       pmGetContextHostName  returns a pointer to a static buffer, so the returned value is only valid until the
       next call to pmGetContextHostName and hence is not thread-safe.  Multi-threaded applications  should  use
       pmGetHostName or pmGetContextHostName_r instead.

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

       PCPIntro(1),  PMAPI(3), gethostname(3), pmDupContext(3), pmErrStr_r(3), pmFetch(3), pmGetArchiveLabel(3),
       pmNewContext(3), pcp.conf(5) and pcp.env(5).

Performance Co-Pilot                                   PCP                               PMGETCONTEXTHOSTNAME(3)