pmparsehostspec(3) — Linux manual page


PMPARSEHOSTSPEC(3)      Library Functions Manual      PMPARSEHOSTSPEC(3)

NAME         top

       __pmParseHostSpec, __pmUnparseHostSpec, __pmFreeHostSpec -
       uniform host specification parser

C SYNOPSIS         top

       #include "pmapi.h"
       #include "libpcp.h"

       int __pmParseHostSpec(const char *string, pmHostSpec **hostsp,
               int *count, char **errmsg);
       int __pmUnparseHostSpec(pmHostSpec *hosts, int count, char
               *string, size_t size);
       void __pmFreeHostSpec(pmHostSpec *hosts, int count);

       cc ... -lpcp

CAVEAT         top

       This documentation is intended for internal Performance Co-Pilot
       (PCP) developer use.

       These interfaces are not part of the PCP APIs that are guaranteed
       to remain fixed across releases, and they may not work, or may
       provide different semantics at some point in the future.

DESCRIPTION         top

       __pmParseHostSpec accepts a string specifying the location of a
       PCP performance metric collector daemon.  The syntax of the
       various formats of this string is described in PCPIntro(1) where
       several examples are also presented.

       The syntax allows the initial pmcd(1) hostname to be optionally
       followed by a list of port numbers, which will be tried in order
       when connecting to pmcd on that host.  The portlist is separated
       from the hostname using a colon, and each port in the list is

       In addition, one or more optional pmproxy(1) hosts can be
       specified (currently, only one proxy host is supported by the PCP
       protocols).  These are separated from each other and from the
       pmcd component using the @ character.  These may also be followed
       by an optional port list, using the same comma-separated syntax
       as before.

       __pmParseHostSpec takes a null-terminated host specification
       string and returns an array of pmHostSpec structures, where the
       array has count entries.

       These pmHostSpec structures that are returned via hostsp
       represent each individual host in the specification string and
       has the following declaration:

           typedef struct {
               char    *name;       /* hostname (always valid) */
               int     *ports;      /* array of host port numbers */
               int     nports;      /* number of ports in host port array */
           } pmHostSpec;

       __pmUnparseHostSpec performs the inverse operation, creating a
       string representation from a number of hosts structures.  Where
       the count of structures indicated by hosts is greater than one,
       the proxy syntax is used to indicate a chain of proxied hosts.
       The size of the supplied string buffer must be provided by the
       caller using the size parameter.

RETURN VALUE         top

       If the given string is successfully parsed __pmParseHostSpec
       returns zero.  In this case the dynamic storage allocated by
       __pmParseHostSpec can be released by calling __pmFreeHostSpec
       using the address returned from __pmParseHostSpec via hosts.

       __pmParseHostSpec returns PM_ERR_GENERIC and a dynamically
       allocated error message string in errmsg, if the given string
       does not parse, and the user-supplied errmsg pointer is non-null.
       Be sure to free(3) the error message string in this situation.

       In the case of an error, hosts is undefined.  In the case of
       success, errmsg is undefined.

       On success __pmUnparseHostSpec returns a positive value
       indicating the number of characters written into the supplied
       buffer.  However, if the supplied buffer was too small, a
       negative status code of -E2BIG is returned.

SEE ALSO         top

       pmcd(1), pmproxy(1), pmchart(1), __pmParseHostAttrsSpec(3),
       PMAPI(3) and pmNewContext(3).

COLOPHON         top

       This page is part of the PCP (Performance Co-Pilot) project.
       Information about the project can be found at 
       ⟨⟩.  If you have a bug report for this manual
       page, send it to  This page was obtained from the
       project's upstream Git repository
       ⟨⟩ on 2023-12-22.
       (At that time, the date of the most recent commit that was found
       in the repository was 2023-12-16.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
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       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

Performance Co-Pilot               PCP                PMPARSEHOSTSPEC(3)

Pages that refer to this page: pmparsehostattrsspec(3)