librrd(3)                           rrdtool                          librrd(3)

NAME
       librrd - RRD library functions

DESCRIPTION
       librrd contains most of the functionality in RRDtool.  The command line
       utilities and language bindings are often just wrappers around the code
       contained in librrd.

       This manual page documents the librrd API.

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

CORE FUNCTIONS
       rrd_dump_cb_r(char *filename, int opt_header, rrd_output_callback_t cb,
       void *user)
           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  rrd_dump_cb_r  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 resulting string in memory.

           The arguments for rrd_dump_cb_r are the same as for  rrd_dump_opt_r
           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  rrd_dump_opt_r  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 rrd_dump_cb_r 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
           rrd_dump_opt_cb_fileout   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 rrd_dump_cb_r respectively.

       rrd_fetch_cb_register(rrd_fetch_cb_t c)
           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
           rrd_fetch_cb_register function.

           The argument signature and api must be the  same  of  the  callback
           function  and  must  be  equivalent  to  the one of rrd_fetch_fn in
           rrd__fetch.c.

           To activate the callback function you can use the  pseudo  filename
           cb//free__form__text.

           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.

UTILITY FUNCTIONS
       rrd_random()
           Generates  random numbers just like random().  This further ensures
           that the  random  number  generator  is  seeded  exactly  once  per
           process.

       rrd_strtodbl
           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.

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

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

       rrd_add_ptr(void ***dest, size_t *dest_size, void *src)
           Dynamically  resize the array pointed to by "dest".  "dest_size" is
           a  pointer  to  the  current  size  of  "dest".   Upon   successful
           realloc(),  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();

       rrd_add_ptr_chunk(void ***dest, size_t *dest_size, void *src, size_t
       *alloc, size_t chunk)
           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 accordingly.  "alloc" must be >= "dest_size".

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

       rrd_add_strdup(char ***dest, size_t *dest_size, char *src)
           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();

       rrd_add_strdup_chunk(char ***dest, size_t *dest_size, char *src, size_t
       *alloc, size_t chunk)
           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 accordingly.  "alloc" must be >=
           "dest_size".

       rrd_free_ptrs(void ***src, size_t *cnt)
           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 */

       rrd_mkdir_p(const char *pathname, mode_t mode)
           Create the directory named "pathname" including all of  its  parent
           directories  (similar  to  "mkdir  -p"  on  the  command line - see
           mkdir(1) for more information). The argument "mode"  specifies  the
           permissions  to  use.  It is modified by the process's "umask". See
           mkdir(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 mkdir(2), the function may fail  with  the  following
           errors:

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

           ENOMEM
               Insufficient memory was available.

           any error returned by stat(2)

           In  contrast  to mkdir(2), the function does not fail if "pathname"
           already exists and is a directory.

       rrd_scaled_duration (const char ** token, unsigned long divisor,
       unsigned long ** valuep)
           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
           representing  the  duration in seconds and dividing by some scaling
           factor.  For example, if a user would  natively  express  a  3  day
           archive  of  samples 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
           encoding 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 duration "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  returns  a  text  diagnostic suitable for use in user
           error messages.

CLIENT FUNCTIONS
       The following functions are used to connected to an rrdcached instance,
       either via a unix or  inet  address,  and  create,  update,  or  gather
       statistics about a specified RRD database file.

       There are two different interfaces: The rrd_client_ family of functions
       operate  on  a  user-provided  client object (rrd_client_t) and support
       multiple concurrent connections  to  rrdcache  instances.  The  simpler
       rrdc_  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.

       rrd_client_new(const char *daemon_addr)
           Create a new client connection object. If specified, connect to the
           daemon  at  "daemon_addr".  The  connection can later be changed by
           calling rrd_client_connect.

       rrd_client_destroy(rrd_client_t *client)
           Close a client connection and destroy the  object  by  freeing  all
           dynamically allocated memory. After calling this function, "client"
           can no longer be used.

       rrd_client_connect(rrd_client_t *client, const char *daemon_addr)
       rrdc_connect(const char *daemon_addr)
           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 address.

       rrd_client_is_connected(rrd_client_t *client)
           Return a boolean int if the client is connected to the server.

       rrd_client_address(rrd_client_t *client)
           Returns the server address belonging to the current connection.

       rrdc_is_connected(const char *daemon_addr)
           Return a boolean int to determine if the client is connected to the
           rrdcache daemon specified by the "daemon_addr" parameter.

       rrd_client_ping(rrd_client_t *client)
       rrdc_ping
           Check the client connection by pinging the remote side.

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

       rrd_client_disconnect(rrd_client_t *client)
       rrdc_disconnect
           Disconnect gracefully from the present daemon connection.

       rrd_client_update(rrd_client_t *client, const char *filename, int
       values_num, const char ** const *values)
       rrdc_update(const char *filename, int values_num, const char ** const
       *values)
           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.

       rrd_client_info(rrd_client_t *client, const char *filename)
       rrdc_info(const char *filename)
           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;

       rrd_client_last(rrd_client_t *client, const char *filename)
       rrdc_last(const char *filename)
           Grab the unix epoch of the last time RRD "filename" was updated.

       rrd_client_first(rrd_client_t *client, const char *filename, int
       rraindex)
       rrdc_first(const char *filename, int rraindex)
           Get the first value of the first sample of the RRD  "filename",  of
           the  "rraindex"  RRA  (Round  Robin Archive) index number.  The RRA
           index number can be determined by pulling the  rrd_info_t  off  the
           RRD.

       rrd_client_create(rrd_client_t *client, const char *filename, unsigned
       long pdp_step, time_t last_up, int no_overwrite, int argc, const char
       **argv)
       rrdc_create(const char *filename, unsigned long pdp_step, time_t
       last_up, int no_overwrite, int argc, const char **argv)
           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  existing  RRD if one is found with the same
           filename; "no_overwrite".

       rrdc_create_r2(rrd_client_t *client, const char *filename, unsigned
       long pdp_step, time_t last_up, int no_overwrite, const char **sources,
       const char *template, int argc, const char **argv)
       rrdc_create_r2(const char *filename, unsigned long pdp_step, time_t
       last_up, int no_overwrite, const char **sources, const char *template,
       int argc, const char **argv)
           Create an RRD database in the daemon. rrdc_create_r2 has  the  same
           parameters  as  rrdc_create with two added parameters of; "sources"
           and "template".

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

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

       rrd_client_flush(rrd_client_t *client, const char *filename)
       rrdc_flush(const char *filename)
           flush  the  currently  RRD  cached  in  the  daemon  specified  via
           "filename".

       rrd_client_forget(rrd_client_t *client, const char *filename)
       rrdc_forget(const char *filename)
           Drop the cached data for the RRD file specified via "filename".

       rrdc_flush_if_daemon(const char *daemon_addr, const char *filename)
           Flush  the  specified  RRD  given  by "filename" only if the daemon
           "daemon_addr" is up and connected.

       rrd_client_fetch(rrd_client_t *client, const char *filename, const char
       *cf, time_t *ret_start, time_t *ret_end, unsigned long *ret_step,
       unsigned long *ret_ds_num, char ***ret_ds_names, rrd_value_t
       **ret_data)
       rrdc_fetch(const char *filename, const char *cf, time_t *ret_start,
       time_t *ret_end, unsigned long *ret_step, unsigned long *ret_ds_num,
       char ***ret_ds_names, rrd_value_t **ret_data)
           Perform a fetch operation on the specified RRD  Database  given  be
           "filename",  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.

       rrdc_stats_get(rrd_client_t *client, rrdc_stats_t **ret_stats)
       rrdc_stats_get(rrdc_stats_t **ret_stats)
           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;

       rrdc_stats_free(rrdc_stats_t *ret_stats)
           Free the stats struct allocated via rrdc_stats_get.

   SEE ALSO
       rrcached(1) rrdfetch(1) rrdinfo(1) rrdlast(1) rrdcreate(1) rrdupdate(1)
       rrdlast(1)

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

1.10.2                            2026-05-19                         librrd(3)
