1librrd(3) rrdtool librrd(3)
2
6 librrd - RRD library functions
7
9 librrd contains most of the functionality in RRDTool. The command line
10 utilities and language bindings are often just wrappers around the code
11 contained in librrd.
12 This manual page documents the librrd API.
14 NOTE: This document is a work in progress, and should be considered
16 incomplete as long as this warning persists. For more information
17 about the librrd functions, always consult the source code.
18
20 rrd_dump_cb_r(char *filename, int opt_header, rrd_output_callback_t cb,
21 void *user)
22 In some situations it is necessary to get the output of "rrd_dump"
23 without writing it to a file or the standard output. In such cases
24 an application can ask rrd_dump_cb_r to call an user-defined
25 function each time there is output to be stored somewhere. This can
26 be used, to e.g. directly feed an XML parser with the dumped output
27 or transfer the resulting string in memory.
28 The arguments for rrd_dump_cb_r are the same as for rrd_dump_opt_r
30 except that the output filename parameter is replaced by the user-
31 defined callback function and an additional parameter for the
32 callback function that is passed untouched, i.e. to store
33 information about the callback state needed for the user-defined
34 callback to function properly.
35 Recent versions of rrd_dump_opt_r internally use this callback
37 mechanism to write their output to the file provided by the user.
38 size_t rrd_dump_opt_cb_fileout(
40 const void *data,
41 size_t len,
42 void *user)
43 {
44 return fwrite(data, 1, len, (FILE *)user);
45 }
46 The associated call for rrd_dump_cb_r looks like
48 res = rrd_dump_cb_r(filename, opt_header,
50 rrd_dump_opt_cb_fileout, (void *)out_file);
51 where the last parameter specifies the file handle
53 rrd_dump_opt_cb_fileout should write to. There's no specific
54 condition for the callback to detect when it is called for the
55 first time, nor for the last time. If you require this for
56 initialization and cleanup you should do those tasks before and
57 after calling rrd_dump_cr_r respectively.
58
60 rrd_random()
61 Generates random numbers just like random(). This further ensures
62 that the random number generator is seeded exactly once per
63 process.
64 rrd_add_ptr(void ***dest, size_t *dest_size, void *src)
66 Dynamically resize the array pointed to by "dest". "dest_size" is
67 a pointer to the current size of "dest". Upon successful
68 realloc(), the "dest_size" is incremented by 1 and the "src"
69 pointer is stored at the end of the new "dest". Returns 1 on
70 success, 0 on failure.
71 type **arr = NULL;
73 type *elem = "whatever";
74 size_t arr_size = 0;
75 if (!rrd_add_ptr(&arr, &arr_size, elem))
76 handle_failure();
77 rrd_add_strdup(char ***dest, size_t *dest_size, char *src)
79 Like "rrd_add_ptr", except adds a "strdup" of the source string.
80 char **arr = NULL;
82 size_t arr_size = NULL;
83 char *str = "example text";
84 if (!rrd_add_strdup(&arr, &arr_size, str))
85 handle_failure();
86 rrd_free_ptrs(void ***src, size_t *cnt)
88 Free an array of pointers allocated by "rrd_add_ptr" or
89 "rrd_add_strdup". Also frees the array pointer itself. On return,
90 the source pointer will be NULL and the count will be zero.
91 /* created as above */
93 rrd_free_ptrs(&arr, &arr_size);
94 /* here, arr == NULL && arr_size == 0 */
95 rrd_mkdir_p(const char *pathname, mode_t mode)
97 Create the directory named "pathname" including all of its parent
98 directories (similar to "mkdir -p" on the command line - see
99 mkdir(1) for more information). The argument "mode" specifies the
100 permissions to use. It is modified by the process's "umask". See
101 mkdir(2) for more details.
102 The function returns 0 on success, a negative value else. In case
104 of an error, "errno" is set accordingly. Aside from the errors
105 documented in mkdir(2), the function may fail with the following
106 errors:
107 EINVAL
109 "pathname" is "NULL" or the empty string.
110 ENOMEM
112 Insufficient memory was available.
113 any error returned by stat(2)
115 In contrast to mkdir(2), the function does not fail if "pathname"
117 already exists and is a directory.
118
120 RRD Contributors <rrd-developers@lists.oetiker.ch>
1211.4.4 2009-11-15 librrd(3)