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sd_journal_test_cursor(3) [centos man page]

SD_JOURNAL_GET_CURSOR(3)				       sd_journal_get_cursor					  SD_JOURNAL_GET_CURSOR(3)

NAME
sd_journal_get_cursor, sd_journal_test_cursor - Get cursor string for or test cursor string against the current journal entry SYNOPSIS
#include <systemd/sd-journal.h> int sd_journal_get_cursor(sd_journal* j, char ** cursor); int sd_journal_test_cursor(sd_journal* j, const char * cursor); DESCRIPTION
sd_journal_get_cursor() returns a cursor string for the current journal entry. A cursor is a serialization of the current journal position formatted as text. The string only contains printable characters and can be passed around in text form. The cursor identifies a journal entry globally and in a stable way and may be used to later seek to it via sd_journal_seek_cursor(3). The cursor string should be considered opaque and not be parsed by clients. Seeking to a cursor position without the specific entry being available locally will seek to the next closest (in terms of time) available entry. The call takes two arguments: a journal context object and a pointer to a string pointer where the cursor string will be placed. The string is allocated via libc malloc(3) and should be freed after use with free(3). Note that sd_journal_get_cursor() 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_test_cursor() may be used to check whether the current position in the journal matches the specified cursor. This is useful since cursor strings do not uniquely identify an entry: the same entry might be referred to by multiple different cursor strings, and hence string comparing cursors is not possible. Use this call to verify after an invocation of sd_journal_seek_cursor(3) whether the entry being sought to was actually found in the journal or the next closest entry was used instead. RETURN VALUE
sd_journal_get_cursor() returns 0 on success or a negative errno-style error code. sd_journal_test_cursor() returns positive if the current entry matches the specified cursor, 0 if it does not match the specified cursor or a negative errno-style error code on failure. NOTES
The sd_journal_get_cursor() and sd_journal_test_cursor() interfaces are available as a shared library, which can be compiled and linked to with the libsystemd-journal pkg-config(1) file. SEE ALSO
systemd(1), sd-journal(3), sd_journal_open(3), sd_journal_seek_cursor(3) systemd 208 SD_JOURNAL_GET_CURSOR(3)

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SD_JOURNAL_SEEK_HEAD(3) 				       sd_journal_seek_head					   SD_JOURNAL_SEEK_HEAD(3)

NAME
sd_journal_seek_head, sd_journal_seek_tail, sd_journal_seek_monotonic_usec, sd_journal_seek_realtime_usec, sd_journal_seek_cursor - Seek to a position in the journal SYNOPSIS
#include <systemd/sd-journal.h> int sd_journal_seek_head(sd_journal* j); int sd_journal_seek_tail(sd_journal* j); int sd_journal_seek_monotonic_usec(sd_journal* j, sd_id128_t boot_id, uint64_t usec); int sd_journal_seek_realtime_usec(sd_journal* j, uint64_t usec); int sd_journal_seek_cursor(sd_journal* j, const char * cursor); DESCRIPTION
sd_journal_seek_head() seeks to the beginning of the journal, i.e. the oldest available entry. Similarly, sd_journal_seek_tail() may be used to seek to the end of the journal, i.e. the most recent available entry. sd_journal_seek_monotonic_usec() seeks to the entry with the specified monotonic timestamp, i.e. CLOCK_MONOTONIC. Since monotonic time restarts on every reboot a boot ID needs to be specified as well. sd_journal_seek_realtime_usec() seeks to the entry with the specified realtime (wallclock) timestamp, i.e. CLOCK_REALTIME. Note that the realtime clock is not necessarily monotonic. If a realtime timestamp is ambiguous, it is not defined which position is sought to. sd_journal_seek_cursor() seeks to the entry located at the specified cursor string. For details on cursors, see sd_journal_get_cursor(3). If no entry matching the specified cursor is found the call will seek to the next closest entry (in terms of time) instead. To verify whether the newly selected entry actually matches the cursor, use sd_journal_test_cursor(3). Note that these calls do not actually make any entry the new current entry, this needs to be done in a separate step with a subsequent sd_journal_next(3) invocation (or a similar call). Only then, entry data may be retrieved via sd_journal_get_data(3). If no entry exists that matches exactly the specified seek address, the next closest is sought to. If sd_journal_next(3) is used, the closest following entry will be sought to, if sd_journal_previous(3) is used the closest preceding entry is sought to. RETURN VALUE
The functions return 0 on success or a negative errno-style error code. NOTES
The sd_journal_seek_head(), sd_journal_seek_tail(), sd_journal_seek_monotonic_usec(), sd_journal_seek_realtime_usec(), and sd_journal_seek_cursor() interfaces are available as a shared library, which can be compiled and linked to with the libsystemd-journal pkg- config(1) file. SEE ALSO
systemd(1), sd-journal(3), sd_journal_open(3), sd_journal_next(3), sd_journal_get_data(3), sd_journal_get_cursor(3), sd_journal_get_realtime_usec(3) systemd 208 SD_JOURNAL_SEEK_HEAD(3)

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