man/sd_journal_get_cursor.3

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   2 .TH "SD_JOURNAL_GET_CURSOR" "3" "" "systemd 214" "sd_journal_get_cursor"
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   7 .\" http://bugs.debian.org/507673
   8 .\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
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  22 .SH "NAME"
  23 sd_journal_get_cursor, sd_journal_test_cursor \- Get cursor string for or test cursor string against the current journal entry
  24 .SH "SYNOPSIS"
  25 .sp
  26 .ft B
  27 .nf
  28 #include <systemd/sd\-journal\&.h>
  29 .fi
  30 .ft
  31 .HP \w'int\ sd_journal_get_cursor('u
  32 .BI "int sd_journal_get_cursor(sd_journal\ *" "j" ", char\ **" "cursor" ");"
  33 .HP \w'int\ sd_journal_test_cursor('u
  34 .BI "int sd_journal_test_cursor(sd_journal\ *" "j" ", const\ char\ *" "cursor" ");"
  35 .SH "DESCRIPTION"
  36 .PP
  37 \fBsd_journal_get_cursor()\fR
  38 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
  39 \fBsd_journal_seek_cursor\fR(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
  40 \fBmalloc\fR(3)
  41 and should be freed after use with
  42 \fBfree\fR(3)\&.
  43 .PP
  44 Note that
  45 \fBsd_journal_get_cursor()\fR
  46 will not work before
  47 \fBsd_journal_next\fR(3)
  48 (or related call) has been called at least once, in order to position the read pointer at a valid entry\&.
  49 .PP
  50 \fBsd_journal_test_cursor()\fR
  51 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
  52 \fBsd_journal_seek_cursor\fR(3)
  53 whether the entry being sought to was actually found in the journal or the next closest entry was used instead\&.
  54 .SH "RETURN VALUE"
  55 .PP
  56 \fBsd_journal_get_cursor()\fR
  57 returns 0 on success or a negative errno\-style error code\&.
  58 \fBsd_journal_test_cursor()\fR
  59 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\&.
  60 .SH "NOTES"
  61 .PP
  62 The
  63 \fBsd_journal_get_cursor()\fR
  64 and
  65 \fBsd_journal_test_cursor()\fR
  66 interfaces are available as a shared library, which can be compiled and linked to with the
  67 \fBlibsystemd\fR\ \&\fBpkg-config\fR(1)
  68 file\&.
  69 .SH "SEE ALSO"
  70 .PP
  71 \fBsystemd\fR(1),
  72 \fBsd-journal\fR(3),
  73 \fBsd_journal_open\fR(3),
  74 \fBsd_journal_seek_cursor\fR(3)