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.\" ========================================================================
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.TH librrd 3 "2009-11-15" "1.4.3" "rrdtool"
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.\" For nroff, turn off justification. Always turn off hyphenation; it makes
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.\" way too many mistakes in technical documents.
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librrd \- RRD library functions
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.IX Header "DESCRIPTION"
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\&\fBlibrrd\fR contains most of the functionality in \fBRRDTool\fR. The command
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line utilities and language bindings are often just wrappers around the
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code contained in \fBlibrrd\fR.
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This manual page documents the \fBlibrrd\fR \s-1API\s0.
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\&\fB\s-1NOTE:\s0\fR This document is a work in progress, and should be considered
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incomplete as long as this warning persists. For more information about
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the \fBlibrrd\fR functions, always consult the source code.
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.IX Header "CORE FUNCTIONS"
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.IP "\fBrrd_dump_cb_r(char *filename, int opt_header, rrd_output_callback_t cb, void *user)\fR" 4
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.IX Item "rrd_dump_cb_r(char *filename, int opt_header, rrd_output_callback_t cb, void *user)"
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In some situations it is necessary to get the output of \f(CW\*(C`rrd_dump\*(C'\fR without
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writing it to a file or the standard output. In such cases an application
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can ask \fBrrd_dump_cb_r\fR to call an user-defined function each time there
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is output to be stored somewhere. This can be used, to e.g. directly feed
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an \s-1XML\s0 parser with the dumped output or transfer the resulting string
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The arguments for \fBrrd_dump_cb_r\fR are the same as for \fBrrd_dump_opt_r\fR
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except that the output filename parameter is replaced by the user-defined
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callback function and an additional parameter for the callback function
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that is passed untouched, i.e. to store information about the callback state
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needed for the user-defined callback to function properly.
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Recent versions of \fBrrd_dump_opt_r\fR internally use this callback mechanism
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to write their output to the file provided by the user.
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\& size_t rrd_dump_opt_cb_fileout(
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\& return fwrite(data, 1, len, (FILE *)user);
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The associated call for \fBrrd_dump_cb_r\fR looks like
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\& res = rrd_dump_cb_r(filename, opt_header,
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\& rrd_dump_opt_cb_fileout, (void *)out_file);
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where the last parameter specifies the file handle \fBrrd_dump_opt_cb_fileout\fR
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should write to. There's no specific condition for the callback to detect
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when it is called for the first time, nor for the last time. If you require
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this for initialization and cleanup you should do those tasks before and
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after calling \fBrrd_dump_cr_r\fR respectively.
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.SH "UTILITY FUNCTIONS"
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.IX Header "UTILITY FUNCTIONS"
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.IP "\fB\f(BIrrd_random()\fB\fR" 4
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.IX Item "rrd_random()"
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Generates random numbers just like \fIrandom()\fR. This further ensures that
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the random number generator is seeded exactly once per process.
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.IP "\fBrrd_add_ptr(void ***dest, size_t *dest_size, void *src)\fR" 4
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.IX Item "rrd_add_ptr(void ***dest, size_t *dest_size, void *src)"
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Dynamically resize the array pointed to by \f(CW\*(C`dest\*(C'\fR. \f(CW\*(C`dest_size\*(C'\fR is a
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pointer to the current size of \f(CW\*(C`dest\*(C'\fR. Upon successful \fIrealloc()\fR, the
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\&\f(CW\*(C`dest_size\*(C'\fR is incremented by 1 and the \f(CW\*(C`src\*(C'\fR pointer is stored at the
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end of the new \f(CW\*(C`dest\*(C'\fR. Returns 1 on success, 0 on failure.
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\& type **arr = NULL;
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\& type *elem = "whatever";
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\& size_t arr_size = 0;
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\& if (!rrd_add_ptr(&arr, &arr_size, elem))
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.IP "\fBrrd_add_strdup(char ***dest, size_t *dest_size, char *src)\fR" 4
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.IX Item "rrd_add_strdup(char ***dest, size_t *dest_size, char *src)"
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Like \f(CW\*(C`rrd_add_ptr\*(C'\fR, except adds a \f(CW\*(C`strdup\*(C'\fR of the source string.
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\& char **arr = NULL;
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\& size_t arr_size = NULL;
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\& char *str = "example text";
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\& if (!rrd_add_strdup(&arr, &arr_size, str))
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.IP "\fBrrd_free_ptrs(void ***src, size_t *cnt)\fR" 4
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.IX Item "rrd_free_ptrs(void ***src, size_t *cnt)"
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Free an array of pointers allocated by \f(CW\*(C`rrd_add_ptr\*(C'\fR or
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\&\f(CW\*(C`rrd_add_strdup\*(C'\fR. Also frees the array pointer itself. On return, the
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source pointer will be \s-1NULL\s0 and the count will be zero.
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\& /* created as above */
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\& rrd_free_ptrs(&arr, &arr_size);
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\& /* here, arr == NULL && arr_size == 0 */
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.IP "\fBrrd_mkdir_p(const char *pathname, mode_t mode)\fR" 4
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.IX Item "rrd_mkdir_p(const char *pathname, mode_t mode)"
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Create the directory named \f(CW\*(C`pathname\*(C'\fR including all of its parent
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directories (similar to \f(CW\*(C`mkdir \-p\*(C'\fR on the command line \- see \fImkdir\fR\|(1) for
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more information). The argument \f(CW\*(C`mode\*(C'\fR specifies the permissions to use. It
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is modified by the process's \f(CW\*(C`umask\*(C'\fR. See \fImkdir\fR\|(2) for more details.
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The function returns 0 on success, a negative value else. In case of an error,
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\&\f(CW\*(C`errno\*(C'\fR is set accordingly. Aside from the errors documented in \fImkdir\fR\|(2),
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the function may fail with the following errors:
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.IP "\fB\s-1EINVAL\s0\fR" 4
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\&\f(CW\*(C`pathname\*(C'\fR is \f(CW\*(C`NULL\*(C'\fR or the empty string.
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.IP "\fB\s-1ENOMEM\s0\fR" 4
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Insufficient memory was available.
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.IP "\fBany error returned by \f(BIstat\fB\|(2)\fR" 4
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.IX Item "any error returned by stat"
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In contrast to \fImkdir\fR\|(2), the function does \fBnot\fR fail if \f(CW\*(C`pathname\*(C'\fR
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already exists and is a directory.
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\&\s-1RRD\s0 Contributors <rrd\-developers@lists.oetiker.ch>
added
removed
doc/librrd.3
