sd_journal_get_data_threshold man page on Mageia

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SD_JOURNAL_GET_DATA(3)	      sd_journal_get_data	SD_JOURNAL_GET_DATA(3)

NAME
       sd_journal_get_data, sd_journal_enumerate_data,
       sd_journal_restart_data, SD_JOURNAL_FOREACH_DATA,
       sd_journal_set_data_threshold, sd_journal_get_data_threshold - Read
       data fields from the current journal entry

SYNOPSIS
       #include <systemd/sd-journal.h>

       int sd_journal_get_data(sd_journal* j, const char* field,
			       const void** data, size_t* length);

       int sd_journal_enumerate_data(sd_journal* j, const void** data,
				     size_t* length);

       void sd_journal_restart_data(sd_journal* j);

       SD_JOURNAL_FOREACH_DATA(sd_journal* j, const void* data,
			       size_t length);

       int sd_journal_set_data_threshold(sd_journal* j, size_t sz);

       int sd_journal_get_data_threshold(sd_journal* j, size_t* sz);

DESCRIPTION
       sd_journal_get_data() gets the data object associated with a specific
       field from the current journal entry. It takes four arguments: the
       journal context object, a string with the field name to request, plus a
       pair of pointers to pointer/size variables where the data object and
       its size shall be stored in. The field name should be an entry field
       name. Well-known field names are listed in systemd.journal-fields(7).
       The returned data is in a read-only memory map and is only valid until
       the next invocation of sd_journal_get_data() or
       sd_journal_enumerate_data(), or the read pointer is altered. Note that
       the data returned will be prefixed with the field name and '='. Also
       note that by default data fields larger than 64K might get truncated to
       64K. This threshold may be changed and turned off with
       sd_journal_set_data_threshold() (see below).

       sd_journal_enumerate_data() may be used to iterate through all fields
       of the current entry. On each invocation the data for the next field is
       returned. The order of these fields is not defined. The data returned
       is in the same format as with sd_journal_get_data() and also follows
       the same life-time semantics.

       sd_journal_restart_data() resets the data enumeration index to the
       beginning of the entry. The next invocation of
       sd_journal_enumerate_data() will return the first field of the entry
       again.

       Note that the SD_JOURNAL_FOREACH_DATA() macro may be used as a handy
       wrapper around sd_journal_restart_data() and
       sd_journal_enumerate_data().

       Note that these functions will not work before sd_journal_next(3) (or
       related call) has been called at least once, in order to position the
       read pointer at a valid entry.

       sd_journal_set_data_threshold() may be used to change the data field
       size threshold for data returned by sd_journal_get_data(),
       sd_journal_enumerate_data() and sd_journal_enumerate_unique(). This
       threshold is a hint only: it indicates that the client program is
       interested only in the initial parts of the data fields, up to the
       threshold in size -- but the library might still return larger data
       objects. That means applications should not rely exclusively on this
       setting to limit the size of the data fields returned, but need to
       apply a explicit size limit on the returned data as well. This
       threshold defaults to 64K by default. To retrieve the complete data
       fields this threshold should be turned off by setting it to 0, so that
       the library always returns the complete data objects. It is recommended
       to set this threshold as low as possible since this relieves the
       library from having to decompress large compressed data objects in
       full.

       sd_journal_get_data_threshold() returns the currently configured data
       field size threshold.

RETURN VALUE
       sd_journal_get_data() returns 0 on success or a negative errno-style
       error code. If the current entry does not include the specified field,
       -ENOENT is returned. If sd_journal_next(3) has not been called at least
       once, -EADDRNOTAVAIL is returned.  sd_journal_enumerate_data() returns
       a positive integer if the next field has been read, 0 when no more
       fields are known, or a negative errno-style error code.
       sd_journal_restart_data() returns nothing.
       sd_journal_set_data_threshold() and sd_journal_get_threshold() return 0
       on success or a negative errno-style error code.

NOTES
       The sd_journal_get_data(), sd_journal_enumerate_data(),
       sd_journal_restart_data(), sd_journal_set_data_threshold() and
       sd_journal_get_data_threshold() interfaces are available as a shared
       library, which can be compiled and linked to with the
       libsystemd-journal pkg-config(1) file.

EXAMPLES
       See sd_journal_next(3) for a complete example how to use
       sd_journal_get_data().

       Use the SD_JOURNAL_FOREACH_DATA macro to iterate through all fields of
       the current journal entry:

	   ...
	   int print_fields(sd_journal *j) {
		   const void *data;
		   size_t l;
		   SD_JOURNAL_FOREACH_DATA(j, data, length)
			   printf("%.*s\n", (int) length, data);
	   }
	   ...

SEE ALSO
       systemd(1), systemd.journal-fields(7), sd-journal(3),
       sd_journal_open(3), sd_journal_next(3),
       sd_journal_get_realtime_usec(3), sd_journal_query_unique(3)

systemd 208						SD_JOURNAL_GET_DATA(3)
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