librrd(3)                           rrdtool                          librrd(3)



NNAAMMEE
       librrd - RRD library functions

DDEESSCCRRIIPPTTIIOONN
       lliibbrrrrdd contains most of the functionality in RRRRDDTTooooll.  The command line
       utilities and language bindings are often just wrappers around the code
       contained in lliibbrrrrdd.

       This manual page documents the lliibbrrrrdd API.

       NNOOTTEE:: This document is a work in progress, and should be considered
       incomplete as long as this warning persists.  For more information
       about the lliibbrrrrdd functions, always consult the source code.

CCOORREE FFUUNNCCTTIIOONNSS
       rrrrdd__dduummpp__ccbb__rr((cchhaarr **ffiilleennaammee,, iinntt oopptt__hheeaaddeerr,, rrrrdd__oouuttppuutt__ccaallllbbaacckk__tt ccbb,,
       vvooiidd **uusseerr))
           In some situations it is necessary to get the output of "rrd_dump"
           without writing it to a file or the standard output. In such cases
           an application can ask rrrrdd__dduummpp__ccbb__rr to call an user-defined
           function each time there is output to be stored somewhere. This can
           be used, to e.g. directly feed an XML parser with the dumped output
           or transfer the resulting string in memory.

           The arguments for rrrrdd__dduummpp__ccbb__rr are the same as for rrrrdd__dduummpp__oopptt__rr
           except that the output filename parameter is replaced by the user-
           defined callback function and an additional parameter for the
           callback function that is passed untouched, i.e. to store
           information about the callback state needed for the user-defined
           callback to function properly.

           Recent versions of rrrrdd__dduummpp__oopptt__rr internally use this callback
           mechanism to write their output to the file provided by the user.

               size_t rrd_dump_opt_cb_fileout(
                   const void *data,
                   size_t len,
                   void *user)
               {
                   return fwrite(data, 1, len, (FILE *)user);
               }

           The associated call for rrrrdd__dduummpp__ccbb__rr looks like

               res = rrd_dump_cb_r(filename, opt_header,
                   rrd_dump_opt_cb_fileout, (void *)out_file);

           where the last parameter specifies the file handle
           rrrrdd__dduummpp__oopptt__ccbb__ffiilleeoouutt should write to. There's no specific
           condition for the callback to detect when it is called for the
           first time, nor for the last time. If you require this for
           initialization and cleanup you should do those tasks before and
           after calling rrrrdd__dduummpp__ccrr__rr respectively.

UUTTIILLIITTYY FFUUNNCCTTIIOONNSS
       _rr_rr_dd____rr_aa_nn_dd_oo_mm_((_))
           Generates random numbers just like _r_a_n_d_o_m_(_).  This further ensures
           that the random number generator is seeded exactly once per
           process.

       rrrrdd__aadddd__ppttrr((vvooiidd ******ddeesstt,, ssiizzee__tt **ddeesstt__ssiizzee,, vvooiidd **ssrrcc))
           Dynamically resize the array pointed to by "dest".  "dest_size" is
           a pointer to the current size of "dest".  Upon successful
           _r_e_a_l_l_o_c_(_), the "dest_size" is incremented by 1 and the "src"
           pointer is stored at the end of the new "dest".  Returns 1 on
           success, 0 on failure.

               type **arr = NULL;
               type *elem = "whatever";
               size_t arr_size = 0;
               if (!rrd_add_ptr(&arr, &arr_size, elem))
                   handle_failure();

       rrrrdd__aadddd__ssttrrdduupp((cchhaarr ******ddeesstt,, ssiizzee__tt **ddeesstt__ssiizzee,, cchhaarr **ssrrcc))
           Like "rrd_add_ptr", except adds a "strdup" of the source string.

               char **arr = NULL;
               size_t arr_size = NULL;
               char *str  = "example text";
               if (!rrd_add_strdup(&arr, &arr_size, str))
                   handle_failure();

       rrrrdd__ffrreeee__ppttrrss((vvooiidd ******ssrrcc,, ssiizzee__tt **ccnntt))
           Free an array of pointers allocated by "rrd_add_ptr" or
           "rrd_add_strdup".  Also frees the array pointer itself.  On return,
           the source pointer will be NULL and the count will be zero.

               /* created as above */
               rrd_free_ptrs(&arr, &arr_size);
               /* here, arr == NULL && arr_size == 0 */

       rrrrdd__mmkkddiirr__pp((ccoonnsstt cchhaarr **ppaatthhnnaammee,, mmooddee__tt mmooddee))
           Create the directory named "pathname" including all of its parent
           directories (similar to "mkdir -p" on the command line - see
           _m_k_d_i_r(1) for more information). The argument "mode" specifies the
           permissions to use. It is modified by the process's "umask". See
           _m_k_d_i_r(2) for more details.

           The function returns 0 on success, a negative value else. In case
           of an error, "errno" is set accordingly. Aside from the errors
           documented in _m_k_d_i_r(2), the function may fail with the following
           errors:

           EEIINNVVAALL
               "pathname" is "NULL" or the empty string.

           EENNOOMMEEMM
               Insufficient memory was available.

           aannyy eerrrroorr rreettuurrnneedd bbyy _ss_tt_aa_tt((22))

           In contrast to _m_k_d_i_r(2), the function does nnoott fail if "pathname"
           already exists and is a directory.

AAUUTTHHOORR
       RRD Contributors <rrd-developers@lists.oetiker.ch>



1.4.7                             2009-11-15                         librrd(3)
