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+'\"macro stdmacro
+.\"
+.\" Copyright (c) 2013 Red Hat.
+.\" Copyright (c) 2000-2004 Silicon Graphics, Inc.  All Rights Reserved.
+.\" 
+.\" This program is free software; you can redistribute it and/or modify it
+.\" under the terms of the GNU General Public License as published by the
+.\" Free Software Foundation; either version 2 of the License, or (at your
+.\" option) any later version.
+.\" 
+.\" This program is distributed in the hope that it will be useful, but
+.\" WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+.\" or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+.\" for more details.
+.\" 
+.\"
+.TH PMGETCONTEXTHOSTNAME 3 "PCP" "Performance Co-Pilot"
+.SH NAME
+\f3pmGetContextHostName\f1,
+\f3pmGetContextHostName_r\f1 \- return the hostname associated with a Performance Co-Pilot context
+.SH "C SYNOPSIS"
+.ft 3
+#include <pcp/pmapi.h>
+.sp
+const char *pmGetContextHostName(int \fIid\fP);
+.br
+char *pmGetContextHostName_r(int \fIid\fP, char *\fIbuf\fP, int \fIbuflen\fP);
+.sp
+cc ... \-lpcp
+.ft 1
+.SH DESCRIPTION
+Given a valid PCP context identifier previously created with
+.BR pmNewContext (3)
+or
+.BR pmDupContext (3),
+the
+.B pmGetContextHostName
+function returns the hostname associated with 
+.IR id .
+The
+.B pmGetContextHostName_r
+function does the same, but stores the result in a user-supplied buffer
+.I buf
+of length
+.IR buflen ,
+which should have room for at least
+.B MAXHOSTNAMELEN
+bytes.
+.PP
+If the context
+.I id
+is associated with an archive source of data, the
+hostname returned is extracted from the archive label using
+.BR pmGetArchiveLabel (3).
+.PP
+For live contexts, an attempt will first be made to retrieve
+the hostname from the PCP collector system using
+.BR pmFetch (3)
+with the
+.I pmcd.hostname
+metric.
+This allows client tools using this interface to retrieve an
+accurate host identifier even in the presence of port forwarding
+and tunnelled connections.
+.PP
+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
+.BR gethostname (3).
+For other contexts, the hostname extracted from the initial
+context host specification will be used.
+.SH "RETURN VALUE"
+If
+.I id
+is not a valid PCP context identifier,
+the returned hostname is a zero length string.
+.SH NOTES
+.B pmGetContextHostName
+returns a pointer to a static buffer,
+so the returned value is only valid until the next call to
+.B pmGetContextHostName
+and hence is not thread-safe.
+Multi-threaded applications should use
+.B pmGetContextHostName_r
+instead.
+.SH "PCP ENVIRONMENT"
+Environment variables with the prefix
+.B PCP_
+are used to parameterize the file and directory names
+used by PCP.
+On each installation, the file
+.I /etc/pcp.conf
+contains the local values for these variables.
+The
+.B $PCP_CONF
+variable may be used to specify an alternative
+configuration file,
+as described in
+.BR pcp.conf (5).
+Values for these variables may be obtained programmatically
+using the
+.BR pmGetConfig (3)
+function.
+.SH SEE ALSO
+.BR PCPIntro (1),
+.BR PMAPI (3),
+.BR gethostname (3),
+.BR pmDupContext (3),
+.BR pmFetch (3),
+.BR pmGetArchiveLabel (3),
+.BR pmNewContext (3),
+.BR pcp.conf (5)
+and
+.BR pcp.env (5).