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sd_journal_seek_head(3) [centos man page]

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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SD_JOURNAL_GET_REALTIME_USEC(3) 			   sd_journal_get_realtime_usec 			   SD_JOURNAL_GET_REALTIME_USEC(3)

NAME
sd_journal_get_realtime_usec, sd_journal_get_monotonic_usec - Read timestamps from the current journal entry SYNOPSIS
#include <systemd/sd-journal.h> int sd_journal_get_realtime_usec(sd_journal* j, uint64_t* usec); int sd_journal_get_monotonic_usec(sd_journal* j, uint64_t* usec, sd_id128_t* boot_id); DESCRIPTION
sd_journal_get_realtime_usec() gets the realtime (wallclock) timestamp of the current journal entry. It takes two arguments: the journal context object and a pointer to a 64-bit unsigned integer to store the timestamp in. The timestamp is in microseconds since the epoch, i.e. CLOCK_REALTIME. sd_journal_get_monotonic_usec() gets the monotonic timestamp of the current journal entry. It takes three arguments: the journal context object, a pointer to a 64-bit unsigned integer to store the timestamp in, as well as a 128-bit ID buffer to store the boot ID of the monotonic timestamp. The timestamp is in microseconds since boot-up of the specific boot, i.e. CLOCK_MONOTONIC. Since the monotonic clock begins new with every reboot, it only defines a well-defined point in time when used together with an identifier identifying the boot. See sd_id128_get_boot(3) for more information. If the boot ID parameter is passed NULL, the function will fail if the monotonic timestamp of the current entry is not of the current system boot. 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. RETURN VALUE
sd_journal_get_realtime_usec() and sd_journal_get_monotonic_usec() returns 0 on success or a negative errno-style error code. If the boot ID parameter was passed NULL and the monotonic timestamp of the current journal entry is not of the current system boot, -ESTALE is returned by sd_journal_get_monotonic_usec(). NOTES
The sd_journal_get_realtime_usec() and sd_journal_get_monotonic_usec() 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_id128_get_boot(3), clock_gettime(2), sd_journal_get_cutoff_realtime_usec(3) systemd 208 SD_JOURNAL_GET_REALTIME_USEC(3)

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