__PMPARSEHOSTATTRSSPEC, __PMUNPARSEHOSTATTRSSPEC, __PMFREEHOSTATTRSSPEC, __PMFREEATTRSSPEC - reference manual online

PMPARSEHOSTATTRSSPEC(3)              Library Functions Manual             PMPARSEHOSTATTRSSPEC(3)

NAME
       __pmParseHostAttrsSpec, __pmUnparseHostAttrsSpec, __pmFreeHostAttrsSpec, __pmFreeAttrsSpec
       - host and attributes specification parser

C SYNOPSIS
       #include <pcp/pmapi.h>
       #include <pcp/impl.h>

       int __pmParseHostAttrsSpec(const char *string, pmHostSpec **hostsp, int *count,
               __pmHashCtl *attrs, char **errmsg);
       int __pmUnparseHostAttrsSpec(pmHostSpec *hostsp, int *count, __pmHashCtl *attrs,
               char *string, size_t size);
       void __pmFreeHostAttrsSpec(pmHostSpec *hosts, int count, __pmHashCtl *attrs);
       void __pmFreeAttrsSpec(__pmHashCtl *attrs);

       cc ... -lpcp

DESCRIPTION
       __pmParseHostAttrsSpec accepts a string specifying the location of a PCP performance met‐
       ric collector daemon, and any attributes that should be associated with the connection to
       that daemon.

       The syntax allows the optional specification of a protocol (native PCP protocol, encrypted
       PCP protocol or unix domain socket protocol).

       If the specified protocol is native PCP protocol, or encrypted PCP protocol, an initial
       pmcd(1) hostname with optional port numbers and optional proxy host, and optional at‐
       tributes which are to be associated with the connection may be specified.  Some examples
       follow:

            pcp://nas1.servers.com:@firewalls.r.us?compress
            pcps://nas1.servers.com?user=otto&pass=blotto&compress

       If the specified protocol is a unix domain socket protocol, the path to the socket in the
       local file system may be specified along with optional attributes which are to be associ‐
       ated with the connection.  For example:

            unix://$PCP_RUN_DIR/pmcd.socket:?compress
            local://my/local/pmcd.socket:?user=otto&pass=blotto&compress

       If the optional protocol component is not specified, then the default setting will be used
       - which is the native PCP binary protocol.  However, this can still be overwritten via the
       environment as described in PCPIntro(1).  If the protocol prefix is specified, it must be
       one of either "pcp://" (clear), "pcps://" (secure, encrypted), "unix://" (authenticated
       local) or "local://" ("unix://" then "pcp://").

       The path specified for the "unix://" and "local://" protocols will always be interpreted
       as an absolute path name. For example, the following are all interpreted identically as
       $PCP_RUN_DIR/pmcd.socket.

            unix://$PCP_RUN_DIR/pmcd.socket
            unix:/$PCP_RUN_DIR/pmcd.socket
            unix:$PCP_RUN_DIR/pmcd.socket

       Refer to __pmParseHostSpec(3) for further details of the host and proxy host components.

       If any optional connection attributes are to be specified, these are separated from the
       hostname component via the '?' character.  Each attribute is separated by the '&' charac‐
       ter, and each can be either a simple attribute flag (such as "compress") or a name=value
       pair (such as "username=fred").

       __pmParseHostAttrsSpec takes a null-terminated host-and-attributes specification string
       and returns an array of pmHostSpec structures, where the array has count entries, and an
       attrs hash table containing any attributes (including the optional protocol, if it was
       specified).

       Full details of the pmHostSpec structures are provided in __pmParseHostSpec(3).

       The __pmHashCtl structure that is filled out on return via attributes, represents each in‐
       dividual attribute in the specification string with any associated value.  It should be
       considered an opaque structure and should be zeroed beforehand.

       The returned hash table control structure can be iterated using one of the supplied itera‐
       tion mechanisms - __pmHashWalkCB (a callback-based mechanism) or __pmHashWalk (a simple
       procedural mechanism).  These provide access to the individual hash nodes, as __pmHashNode
       entries, which provide access to decoded attributes and their (optional) values.

           typedef struct __pmHashNode {
               __pmHashNode    *next;    /* next node in hash bucket (internal) */
               unsigned int    key;      /* key identifying particular attribute */
               void            *data;    /* attributes value (optional, string) */
           } __pmHashNode;

       There are a set number of valid attributes, however these may be extended in future re‐
       leases as new connection parameters become needed.  These can be identified via the
       PCP_ATTR_* macros in the PCP header files.

       __pmUnparseHostSpec performs the inverse operation, creating a string representation from
       hosts and attributes structures.  The size of the supplied string buffer must be provided
       by the caller using the size parameter.

RETURN VALUE
       If the given string is successfully parsed __pmParseHostAttrsSpec returns zero.  In this
       case the dynamic storage allocated by __pmParseHostAttrsSpec can be released by calling
       __pmFreeHostAttrsSpec using the addresses returned from __pmParseHostAttrsSpec

       Alternatively, the hosts and attributes memory can be freed separately, using __pmFree‐
       HostSpec(3) and __pmFreeAttrsSpec.

       __pmParseHostAttrsSpec 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(3C) the error message string in this situation.

       In the case of an error, both hosts and attributes are undefined.  In the case of success,
       errmsg is undefined.

       On success __pmUnparseHostAttrsSpec 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 will be returned.

SEE ALSO
       pmcd(1), pmproxy(1), pmchart(1), __pmParseHostSpec(3), PMAPI(3) and pmNewContext(3).

Performance Co-Pilot                           PCP                        PMPARSEHOSTATTRSSPEC(3)