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'\" t
.TH "SD_JOURNAL_SEEK_HEAD" "3" "" "systemd 256~rc3" "sd_journal_seek_head"
.\" -----------------------------------------------------------------
.\" * Define some portability stuff
.\" -----------------------------------------------------------------
.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.\" http://bugs.debian.org/507673
.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.ie \n(.g .ds Aq \(aq
.el .ds Aq '
.\" -----------------------------------------------------------------
.\" * set default formatting
.\" -----------------------------------------------------------------
.\" disable hyphenation
.nh
.\" disable justification (adjust text to left margin only)
.ad l
.\" -----------------------------------------------------------------
.\" * MAIN CONTENT STARTS HERE *
.\" -----------------------------------------------------------------
.SH "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
.SH "SYNOPSIS"
.sp
.ft B
.nf
#include <systemd/sd\-journal\&.h>
.fi
.ft
.HP \w'int\ sd_journal_seek_head('u
.BI "int sd_journal_seek_head(sd_journal\ *" "j" ");"
.HP \w'int\ sd_journal_seek_tail('u
.BI "int sd_journal_seek_tail(sd_journal\ *" "j" ");"
.HP \w'int\ sd_journal_seek_monotonic_usec('u
.BI "int sd_journal_seek_monotonic_usec(sd_journal\ *" "j" ", sd_id128_t\ " "boot_id" ", uint64_t\ " "usec" ");"
.HP \w'int\ sd_journal_seek_realtime_usec('u
.BI "int sd_journal_seek_realtime_usec(sd_journal\ *" "j" ", uint64_t\ " "usec" ");"
.HP \w'int\ sd_journal_seek_cursor('u
.BI "int sd_journal_seek_cursor(sd_journal\ *" "j" ", const\ char\ *" "cursor" ");"
.SH "DESCRIPTION"
.PP
\fBsd_journal_seek_head()\fR
seeks to the beginning of the journal, i\&.e\&. to the position before the oldest available entry\&.
.PP
Similarly,
\fBsd_journal_seek_tail()\fR
may be used to seek to the end of the journal, i\&.e\&. the position after the most recent available entry\&.
.PP
\fBsd_journal_seek_monotonic_usec()\fR
seeks to a position with the specified monotonic timestamp, i\&.e\&.
\fBCLOCK_MONOTONIC\fR\&. Since monotonic time restarts on every reboot a boot ID needs to be specified as well\&.
.PP
\fBsd_journal_seek_realtime_usec()\fR
seeks to a position with the specified realtime (wallclock) timestamp, i\&.e\&.
\fBCLOCK_REALTIME\fR\&. Note that the realtime clock is not necessarily monotonic\&. If a realtime timestamp is ambiguous, it is not defined which position is sought to\&.
.PP
\fBsd_journal_seek_cursor()\fR
seeks to the position at the specified cursor string\&. For details on cursors, see
\fBsd_journal_get_cursor\fR(3)\&. If no entry matching the specified cursor is found the call will seek to the next closest entry (in terms of time) instead\&.
.PP
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
\fBsd_journal_next\fR(3)
invocation (or a similar call)\&. Only then, entry data may be retrieved via
\fBsd_journal_get_data\fR(3)
or an entry cursor be retrieved via
\fBsd_journal_get_cursor\fR(3)\&. If no entry exists that matches exactly the specified seek address, the next closest is sought to\&. If
\fBsd_journal_next\fR(3)
is used, the closest following entry will be sought to, if
\fBsd_journal_previous\fR(3)
is used the closest preceding entry is sought to\&.
.PP
After the seek is done, and
\fBsd_journal_next\fR(3)
or a similar call has been made,
\fBsd_journal_test_cursor\fR(3)
may be used to verify whether the newly selected entry actually matches the cursor\&.
.SH "RETURN VALUE"
.PP
The functions return 0 on success or a negative errno\-style error code\&.
.SH "NOTES"
.PP
All functions listed here are thread\-agnostic and only a single specific thread may operate on a given object during its entire lifetime\&. It\*(Aqs safe to allocate multiple independent objects and use each from a specific thread in parallel\&. However, it\*(Aqs not safe to allocate such an object in one thread, and operate or free it from any other, even if locking is used to ensure these threads don\*(Aqt operate on it at the very same time\&.
.PP
Functions described here are available as a shared library, which can be compiled against and linked to with the
\fBlibsystemd\fR\ \&\fBpkg-config\fR(1)
file\&.
.SH "HISTORY"
.PP
\fBsd_journal_seek_head()\fR,
\fBsd_journal_seek_tail()\fR,
\fBsd_journal_seek_monotonic_usec()\fR,
\fBsd_journal_seek_realtime_usec()\fR, and
\fBsd_journal_seek_cursor()\fR
were added in version 187\&.
.SH "SEE ALSO"
.PP
\fBsystemd\fR(1), \fBsd-journal\fR(3), \fBsd_journal_open\fR(3), \fBsd_journal_next\fR(3), \fBsd_journal_get_data\fR(3), \fBsd_journal_get_cursor\fR(3), \fBsd_journal_get_realtime_usec\fR(3)
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