'\" t
.TH "SD\-JOURNAL" "3" "" "systemd 256.8" "sd-journal"
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.SH "NAME"
sd-journal \- APIs for submitting and querying log entries to and from the journal
.SH "SYNOPSIS"
.sp
.ft B
.nf
#include <systemd/sd\-journal\&.h>
.fi
.ft
.HP \w'\fBpkg\-config\ \-\-cflags\ \-\-libs\ libsystemd\fR\ 'u
\fBpkg\-config \-\-cflags \-\-libs libsystemd\fR
.SH "DESCRIPTION"
.PP
sd\-journal\&.h
is part of
\fBlibsystemd\fR(3)
and provides APIs to submit and query log entries\&. The APIs exposed act both as client for the
\fBsystemd-journald.service\fR(8)
journal service and as parser for the journal files on disk\&.
.PP
See
\fBsd_journal_print\fR(3),
\fBsd_journal_stream_fd\fR(3),
\fBsd_journal_open\fR(3),
\fBsd_journal_next\fR(3),
\fBsd_journal_get_realtime_usec\fR(3),
\fBsd_journal_add_match\fR(3),
\fBsd_journal_seek_head\fR(3),
\fBsd_journal_enumerate_fields\fR(3),
\fBsd_journal_get_cursor\fR(3),
\fBsd_journal_get_cutoff_realtime_usec\fR(3),
\fBsd_journal_get_cutoff_monotonic_usec\fR(3),
\fBsd_journal_get_usage\fR(3),
\fBsd_journal_get_catalog\fR(3),
\fBsd_journal_get_fd\fR(3),
\fBsd_journal_has_runtime_files\fR(3)
and
\fBsd_journal_has_persistent_files\fR(3)
for more information about the functions implemented\&.
.PP
Command line access for submitting entries to the journal is available with the
\fBsystemd-cat\fR(1)
tool\&. Command line access for querying entries from the journal is available with the
\fBjournalctl\fR(1)
tool\&.
.SH "THREAD SAFETY"
.PP
Functions that operate on
sd_journal
objects are thread agnostic \(em given
sd_journal
pointer may only be used from one specific thread at all times (and it has to be the very same one during the entire lifetime of the object), but multiple, independent threads may use multiple, independent objects safely\&. Other functions \(em those that are used to send entries to the journal, like
\fBsd_journal_print\fR(3)
and similar, or those that are used to retrieve global information like
\fBsd_journal_stream_fd\fR(3)
and
\fBsd_journal_get_catalog_for_message_id\fR(3)
\(em are fully thread\-safe and may be called from multiple threads in parallel\&.
.SH "OPTIONAL DEPENDENCIES"
.PP
Depending on which build\-time options are enabled, functions that operate on
sd_journal
objects might cause optional shared libraries to be dynamically loaded via
\fBdlopen\fR(3), such as decompression libraries (xz, lz4, zstd) or cryptographic libraries (gcrypt)\&.
.SH "NOTES"
.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\&.
.PP
The code described here uses
\fBgetenv\fR(3), which is declared to be not multi\-thread\-safe\&. This means that the code calling the functions described here must not call
\fBsetenv\fR(3)
from a parallel thread\&. It is recommended to only do calls to
\fBsetenv()\fR
from an early phase of the program when no other threads have been started\&.
.SH "SEE ALSO"
.PP
\fBsystemd\fR(1), \fBsd_journal_print\fR(3), \fBsd_journal_stream_fd\fR(3), \fBsd_journal_open\fR(3), \fBsd_journal_next\fR(3), \fBsd_journal_get_data\fR(3), \fBsd_journal_get_realtime_usec\fR(3), \fBsd_journal_add_match\fR(3), \fBsd_journal_seek_head\fR(3), \fBsd_journal_enumerate_fields\fR(3), \fBsd_journal_get_cursor\fR(3), \fBsd_journal_get_cutoff_realtime_usec\fR(3), \fBsd_journal_get_cutoff_monotonic_usec\fR(3), \fBsd_journal_get_usage\fR(3), \fBsd_journal_get_fd\fR(3), \fBsd_journal_query_unique\fR(3), \fBsd_journal_get_catalog\fR(3), \fBsd_journal_has_runtime_files\fR(3), \fBsd_journal_has_persistent_files\fR(3), \fBjournalctl\fR(1), \fBsd-id128\fR(3), \fBpkg-config\fR(1)