_l_i_b_r_r_d(3)                            rrdtool                           _l_i_b_r_r_d(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 incom‐
     plete as long as this warning persists.  For more information about the llii‐‐
     bbrrrrdd 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 a 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  re‐
         sulting string in memory.

         The  arguments for rrrrdd__dduummpp__ccbb__rr are the same as for rrrrdd__dduummpp__oopptt__rr ex‐
         cept 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 mecha‐
         nism 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__ccbb__rr  re‐
         spectively.

     rrrrdd__ffeettcchh__ccbb__rreeggiisstteerr((rrrrdd__ffeettcchh__ccbb__tt cc))
         If  your  data does not reside in rrd files, but you would like to draw
         charts using the rrd_graph  functionality,  you  can  supply  your  own
         rrd_fetch  function  and  register  it  using the rrrrdd__ffeettcchh__ccbb__rreeggiisstteerr
         function.

         The argument signature and api must be the same of the  callback  func‐
         tion and must be equivalent to the one of rrrrdd__ffeettcchh__ffnn in _r_r_d___f_e_t_c_h_._c.

         To  activate  the  callback  function  you  can use the pseudo filename
         _c_b_/_/_f_r_e_e___f_o_r_m___t_e_x_t.

         Note that rrdtool graph will not ask the same rrd for  data  twice.  It
         determines  this  by  building  a key out of the values supplied to the
         fetch function. If the values are the same, the previous answer will be
         used.

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

     rrrrdd__ssttrrttooddbbll
         an rrd aware string to double converter  which  sets  rrd_error  in  if
         there  is a problem and uses the return code exclusively for conversion
         status reporting.

     rrrrdd__ssttrrttoodd
         works like normal strtod, but it  is  locale  independent  (and  thread
         safe)

     rrrrdd__ssnnpprriinnttff
         works   like  normal  snprintf but it is locale independent (and thread
         safe)

     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 rreeaalllloocc(()), 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__ppttrr__cchhuunnkk((vvooiidd ******ddeesstt,, ssiizzee__tt **ddeesstt__ssiizzee,, vvooiidd **ssrrcc,, ssiizzee__tt **aall‐‐
     lloocc,, ssiizzee__tt cchhuunnkk))
         Like  "rrd_add_ptr",  except  the destination is allocated in chunks of
         "chunk".  "alloc" points to the number of  entries  allocated,  whereas
         "dest_size"  points  to the number of valid pointers.  If more pointers
         are needed, "chunk" pointers are allocated and "alloc" is increased ac‐
         cordingly.  "alloc" must be >= "dest_size".

         This method improves performance on hosts with expensive realloc().

     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__aadddd__ssttrrdduupp__cchhuunnkk((cchhaarr ******ddeesstt,, ssiizzee__tt **ddeesstt__ssiizzee,, cchhaarr **ssrrcc,, ssiizzee__tt
     **aalllloocc,, ssiizzee__tt cchhuunnkk))
         Like "rrd_add_strdup", except the destination is allocated in chunks of
         "chunk".  "alloc" points to the number of  entries  allocated,  whereas
         "dest_size"  points  to the number of valid pointers.  If more pointers
         are needed, "chunk" pointers are allocated and "alloc" is increased ac‐
         cordingly.  "alloc" must be >= "dest_size".

     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 di‐
         rectories (similar to "mkdir -p" on the command line - see mmkkddiirr(1) for
         more information). The argument "mode"  specifies  the  permissions  to
         use. It is modified by the process's "umask". See mmkkddiirr(2) for more de‐
         tails.

         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
         mmkkddiirr(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 ssttaatt((22))

         In contrast to mmkkddiirr(2), the function does nnoott fail if  "pathname"  al‐
         ready exists and is a directory.

     rrrrdd__ssccaalleedd__dduurraattiioonn ((ccoonnsstt cchhaarr ** ttookkeenn,, uunnssiiggnneedd lloonngg ddiivviissoorr,, uunnssiiggnneedd
     lloonngg ** vvaalluueepp))
         Parse a token in a context where it contains a count (of seconds or PDP
         instances),  or  a  duration that can be converted to a count by repre‐
         senting the duration in seconds and dividing by  some  scaling  factor.
         For  example,  if a user would natively express a 3 day archive of sam‐
         ples collected every 2 minutes, the sample interval can be  represented
         by "2m" instead of 120, and the archive duration by "3d" (to be divided
         by  120)  instead  of  2160  (3*24*60*60  / 120).  See more examples in
         "STEP, HEARTBEAT, and Rows As Durations" in rrdcreate.

         "token" must be a number with an optional single-character  suffix  en‐
         coding the scaling factor:

         "s" indicates seconds

         "m" indicates minutes.  The value is multiplied by 60.

         "h" indicates hours.  The value is multiplied by 3600 (or "60m").

         "d" indicates days.  The value is multiplied by 86400 (or "24h").

         "w" indicates weeks.  The value is multiplied by 604800 (or "7d").

         "M" indicates  months.   The value is multiplied by 2678400 (or "31d").
             (Note this factor accommodates the maximum  number  of  days  in  a
             month.)

         "y" indicates  years.  The value is multiplied by 31622400 (or "366d").
             (Note this factor accommodates leap years.)

         "divisor" is a positive value representing the duration in  seconds  of
         an interval that the desired result counts.

         "valuep"  is a pointer to where the decoded value will be stored if the
         conversion is successful.

         The initial characters of "token" must be the base-10 representation of
         a positive integer, or the conversion fails.

         If the remainder "token" is empty (no suffix), it is  a  count  and  no
         scaling is performed.

         If  "token"  has  one of the suffixes above, the count is multiplied to
         convert it to a duration in seconds.  The resulting number  of  seconds
         is  divided  by "divisor" to produce a count of intervals each of dura‐
         tion "divisor" seconds.  If division would produce a  remainder  (e.g.,
         "5m" (300 seconds) divided by "90s"), the conversion is invalid.

         If "token" has unrecognized trailing characters the conversion fails.

         The  function  returns  a null pointer if the conversion was successful
         and "valuep" has been updated to the scaled value.  On failure, it  re‐
         turns a text diagnostic suitable for use in user error messages.

CCLLIIEENNTT FFUUNNCCTTIIOONNSS
     The following functions are used to connected to an rrdcached instance, ei‐
     ther  via  a unix or inet address, and create, update, or gather statistics
     about a specified RRD database file.

     There are two different interfaces: The rrrrdd__cclliieenntt__ family of functions op‐
     erate on a user-provided client object (rrrrdd__cclliieenntt__tt) and support  multiple
     concurrent  connections  to rrdcache instances. The simpler rrrrddcc__ family of
     functions handles connections transparently but can only be  used  for  one
     connection at a time.

     All  of  the  following  functions  and  data  types  are  specified in the
     "rrd_client.h" header file.

     rrrrdd__cclliieenntt__nneeww((ccoonnsstt cchhaarr **ddaaeemmoonn__aaddddrr))
         Create a new client connection object. If  specified,  connect  to  the
         daemon at "daemon_addr". The connection can later be changed by calling
         rrrrdd__cclliieenntt__ccoonnnneecctt.

     rrrrdd__cclliieenntt__ddeessttrrooyy((rrrrdd__cclliieenntt__tt **cclliieenntt))
         Close a client connection and destroy the object by freeing all dynami‐
         cally  allocated  memory.  After calling this function, "client" can no
         longer be used.

     rrrrdd__cclliieenntt__ccoonnnneecctt((rrrrdd__cclliieenntt__tt **cclliieenntt,, ccoonnsstt cchhaarr **ddaaeemmoonn__aaddddrr))
     rrrrddcc__ccoonnnneecctt((ccoonnsstt cchhaarr **ddaaeemmoonn__aaddddrr))
         Connect to a running rrdcached instance, specified  via  "daemon_addr".
         Any  previous connection will be closed. If "daemon_addr" is "NULL", it
         defaults to the value of the  "ENV_RRDCACHED_ADDRESS"  environment  ad‐
         dress.

     rrrrdd__cclliieenntt__iiss__ccoonnnneecctteedd((rrrrdd__cclliieenntt__tt **cclliieenntt))
         Return a boolean int if the client is connected to the server.

     rrrrdd__cclliieenntt__aaddddrreessss((rrrrdd__cclliieenntt__tt **cclliieenntt))
         Returns the server address belonging to the current connection.

     rrrrddcc__iiss__ccoonnnneecctteedd((ccoonnsstt cchhaarr **ddaaeemmoonn__aaddddrr))
         Return  a  boolean  int  to determine if the client is connected to the
         rrdcache daemon specified by the "daemon_addr" parameter.

     rrrrdd__cclliieenntt__ppiinngg((rrrrdd__cclliieenntt__tt **cclliieenntt))
     rrrrddcc__ppiinngg
         Check the client connection by pinging the remote side.

     rrrrddcc__iiss__aannyy__ccoonnnneecctteedd
         Return a boolean int if any daemon connections are connected.

     rrrrdd__cclliieenntt__ddiissccoonnnneecctt((rrrrdd__cclliieenntt__tt **cclliieenntt))
     rrrrddcc__ddiissccoonnnneecctt
         Disconnect gracefully from the present daemon connection.

     rrrrdd__cclliieenntt__uuppddaattee((rrrrdd__cclliieenntt__tt **cclliieenntt,, ccoonnsstt cchhaarr **ffiilleennaammee,, iinntt vvaall‐‐
     uueess__nnuumm,, ccoonnsstt cchhaarr ** ccoonnsstt **vvaalluueess))
     rrrrddcc__uuppddaattee((ccoonnsstt cchhaarr **ffiilleennaammee,, iinntt vvaalluueess__nnuumm,, ccoonnsstt cchhaarr ** ccoonnsstt **vvaall‐‐
     uueess))
         Update the RRD "filename" via the rrdcached. Where "values_num" is  the
         number of values to update and "values" are the new values to add.

     rrrrdd__cclliieenntt__iinnffoo((rrrrdd__cclliieenntt__tt **cclliieenntt,, ccoonnsstt cchhaarr **ffiilleennaammee))
     rrrrddcc__iinnffoo((ccoonnsstt cchhaarr **ffiilleennaammee))
         Grab  rrd  info  of the RRD "filename" from the connected cache daemon.
         This function returns an rrd_info_t structure of the following format:

             typedef struct rrd_blob_t {
                 unsigned long size; /* size of the blob */
                 unsigned char *ptr; /* pointer */
             } rrd_blob_t;

             typedef enum rrd_info_type { RD_I_VAL = 0,
                 RD_I_CNT,
                 RD_I_STR,
                 RD_I_INT,
                 RD_I_BLO
             } rrd_info_type_t;

             typedef union rrd_infoval {
                 unsigned long u_cnt;
                 rrd_value_t u_val;
                 char     *u_str;
                 int       u_int;
                 rrd_blob_t u_blo;
             } rrd_infoval_t;

             typedef struct rrd_info_t {
                 char     *key;
                 rrd_info_type_t type;
                 rrd_infoval_t value;
                 struct rrd_info_t *next;
             } rrd_info_t;

     rrrrdd__cclliieenntt__llaasstt((rrrrdd__cclliieenntt__tt **cclliieenntt,, ccoonnsstt cchhaarr **ffiilleennaammee))
     rrrrddcc__llaasstt((ccoonnsstt cchhaarr **ffiilleennaammee))
         Grab the unix epoch of the last time RRD "filename" was updated.

     rrrrdd__cclliieenntt__ffiirrsstt((rrrrdd__cclliieenntt__tt **cclliieenntt,, ccoonnsstt cchhaarr **ffiilleennaammee,, iinntt rrrraaiinnddeexx))
     rrrrddcc__ffiirrsstt((ccoonnsstt cchhaarr **ffiilleennaammee,, iinntt rrrraaiinnddeexx))
         Get the first value of the first sample of the RRD "filename",  of  the
         "rraindex"  RRA (Round Robin Archive) index number.  The RRA index num‐
         ber can be determined by pulling the rrd_info_t off the RRD.

     rrrrdd__cclliieenntt__ccrreeaattee((rrrrdd__cclliieenntt__tt **cclliieenntt,, ccoonnsstt cchhaarr **ffiilleennaammee,, uunnssiiggnneedd lloonngg
     ppddpp__sstteepp,, ttiimmee__tt llaasstt__uupp,, iinntt nnoo__oovveerrwwrriittee,, iinntt aarrggcc,, ccoonnsstt cchhaarr ****aarrggvv))
     rrrrddcc__ccrreeaattee((ccoonnsstt cchhaarr **ffiilleennaammee,, uunnssiiggnneedd lloonngg ppddpp__sstteepp,, ttiimmee__tt llaasstt__uupp,,
     iinntt nnoo__oovveerrwwrriittee,, iinntt aarrggcc,, ccoonnsstt cchhaarr ****aarrggvv))
         Create RRD database of path "filename".  The RRD will have a step  size
         of  "pfp_step", the unix epoch timestamp to start collecting data from.
         The number of data sources and RRAs "argc" and the definitions  of  the
         data sources and RRAs "argv". Lastly whether or not to overwrite an ex‐
         isting RRD if one is found with the same filename; "no_overwrite".

     rrrrddcc__ccrreeaattee__rr22((rrrrdd__cclliieenntt__tt **cclliieenntt,, ccoonnsstt cchhaarr **ffiilleennaammee,, uunnssiiggnneedd lloonngg
     ppddpp__sstteepp,, ttiimmee__tt llaasstt__uupp,, iinntt nnoo__oovveerrwwrriittee,, ccoonnsstt cchhaarr ****ssoouurrcceess,, ccoonnsstt
     cchhaarr **tteemmppllaattee,, iinntt aarrggcc,, ccoonnsstt cchhaarr ****aarrggvv))
     rrrrddcc__ccrreeaattee__rr22((ccoonnsstt cchhaarr **ffiilleennaammee,, uunnssiiggnneedd lloonngg ppddpp__sstteepp,, ttiimmee__tt
     llaasstt__uupp,, iinntt nnoo__oovveerrwwrriittee,, ccoonnsstt cchhaarr ****ssoouurrcceess,, ccoonnsstt cchhaarr **tteemmppllaattee,, iinntt
     aarrggcc,, ccoonnsstt cchhaarr ****aarrggvv))
         Create an RRD database in the daemon. rrrrddcc__ccrreeaattee__rr22 has the same para‐
         meters as rrrrddcc__ccrreeaattee with two added parameters of; "sources" and "tem‐
         plate".

         where  "template"  is  the  file path to a RRD file template, with, the
         form defined in rrrrddccrreeaattee(1),

         The "sources" parameter defines series of file paths with data defined,
         to prefill the RRD with. See rrrrddccrreeaattee(1) for more details.

     rrrrdd__cclliieenntt__fflluusshh((rrrrdd__cclliieenntt__tt **cclliieenntt,, ccoonnsstt cchhaarr **ffiilleennaammee))
     rrrrddcc__fflluusshh((ccoonnsstt cchhaarr **ffiilleennaammee))
         flush the currently RRD cached in the daemon specified via "filename".

     rrrrdd__cclliieenntt__ffoorrggeett((rrrrdd__cclliieenntt__tt **cclliieenntt,, ccoonnsstt cchhaarr **ffiilleennaammee))
     rrrrddcc__ffoorrggeett((ccoonnsstt cchhaarr **ffiilleennaammee))
         Drop the cached data for the RRD file specified via "filename".

     rrrrddcc__fflluusshh__iiff__ddaaeemmoonn((ccoonnsstt cchhaarr **ddaaeemmoonn__aaddddrr,, ccoonnsstt cchhaarr **ffiilleennaammee))
         Flush the specified RRD given by "filename" only if  the  daemon  "dae‐
         mon_addr" is up and connected.

     rrrrdd__cclliieenntt__ffeettcchh((rrrrdd__cclliieenntt__tt **cclliieenntt,, ccoonnsstt cchhaarr **ffiilleennaammee,, ccoonnsstt cchhaarr
     **ccff,, ttiimmee__tt **rreett__ssttaarrtt,, ttiimmee__tt **rreett__eenndd,, uunnssiiggnneedd lloonngg **rreett__sstteepp,, uunnssiiggnneedd
     lloonngg **rreett__ddss__nnuumm,, cchhaarr ******rreett__ddss__nnaammeess,, rrrrdd__vvaalluuee__tt ****rreett__ddaattaa))
     rrrrddcc__ffeettcchh((ccoonnsstt cchhaarr **ffiilleennaammee,, ccoonnsstt cchhaarr **ccff,, ttiimmee__tt **rreett__ssttaarrtt,, ttiimmee__tt
     **rreett__eenndd,, uunnssiiggnneedd lloonngg **rreett__sstteepp,, uunnssiiggnneedd lloonngg **rreett__ddss__nnuumm,, cchhaarr
     ******rreett__ddss__nnaammeess,, rrrrdd__vvaalluuee__tt ****rreett__ddaattaa))
         Perform a fetch operation on the specified RRD Database given be "file‐
         name",  where  "cf"  is  the consolidation function, "ret_start" is the
         start time given by unix epoch, "ret_end" is the endtime. "ret_step" is
         the step size in seconds, "ret_ds_num" the number of  data  sources  in
         the RRD, "ret_ds_names" the names of the data sources, and a pointer to
         an rrd_value_t object to shlep the data.

     rrrrddcc__ssttaattss__ggeett((rrrrdd__cclliieenntt__tt **cclliieenntt,, rrrrddcc__ssttaattss__tt ****rreett__ssttaattss))
     rrrrddcc__ssttaattss__ggeett((rrrrddcc__ssttaattss__tt ****rreett__ssttaattss))
         Get stats from the connected daemon, via a linked list of the following
         structure:

             struct rrdc_stats_s {
                 const char *name;
                 uint16_t type;
                 #define RRDC_STATS_TYPE_GAUGE   0x0001
                 #define RRDC_STATS_TYPE_COUNTER 0x0002
                 uint16_t flags;
                 union {
                     uint64_t counter;
                     double   gauge;
                 } value;
                 struct rrdc_stats_s *next;
             };
             typedef struct rrdc_stats_s rrdc_stats_t;

     rrrrddcc__ssttaattss__ffrreeee((rrrrddcc__ssttaattss__tt **rreett__ssttaattss))
         Free the stats struct allocated via rrrrddcc__ssttaattss__ggeett.

   SSEEEE AALLSSOO
     rrrrccaacchheedd(1)  rrrrddffeettcchh(1)  rrrrddiinnffoo(1)  rrrrddllaasstt(1)  rrrrddccrreeaattee(1) rrrrdduuppddaattee(1)
     rrrrddllaasstt(1)

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

1.10.0                             2026-05-23                          _l_i_b_r_r_d(3)
