mirror of
https://git.proxmox.com/git/systemd
synced 2025-06-02 12:41:51 +00:00
146 lines
6.5 KiB
Groff
146 lines
6.5 KiB
Groff
'\" t
|
|
.TH "SD_JOURNAL_GET_DATA" "3" "" "systemd 219" "sd_journal_get_data"
|
|
.\" -----------------------------------------------------------------
|
|
.\" * 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_get_data, sd_journal_enumerate_data, sd_journal_restart_data, SD_JOURNAL_FOREACH_DATA, sd_journal_set_data_threshold, sd_journal_get_data_threshold \- Read data fields from the current journal entry
|
|
.SH "SYNOPSIS"
|
|
.sp
|
|
.ft B
|
|
.nf
|
|
#include <systemd/sd\-journal\&.h>
|
|
.fi
|
|
.ft
|
|
.HP \w'int\ sd_journal_get_data('u
|
|
.BI "int sd_journal_get_data(sd_journal\ *" "j" ", const\ char\ *" "field" ", const\ void\ **" "data" ", size_t\ *" "length" ");"
|
|
.HP \w'int\ sd_journal_enumerate_data('u
|
|
.BI "int sd_journal_enumerate_data(sd_journal\ *" "j" ", const\ void\ **" "data" ", size_t\ *" "length" ");"
|
|
.HP \w'void\ sd_journal_restart_data('u
|
|
.BI "void sd_journal_restart_data(sd_journal\ *" "j" ");"
|
|
.HP \w'SD_JOURNAL_FOREACH_DATA('u
|
|
.BI "SD_JOURNAL_FOREACH_DATA(sd_journal\ *" "j" ", const\ void\ *" "data" ", size_t\ " "length" ");"
|
|
.HP \w'int\ sd_journal_set_data_threshold('u
|
|
.BI "int sd_journal_set_data_threshold(sd_journal\ *" "j" ", size_t\ " "sz" ");"
|
|
.HP \w'int\ sd_journal_get_data_threshold('u
|
|
.BI "int sd_journal_get_data_threshold(sd_journal\ *" "j" ", size_t\ *" "sz" ");"
|
|
.SH "DESCRIPTION"
|
|
.PP
|
|
\fBsd_journal_get_data()\fR
|
|
gets the data object associated with a specific field from the current journal entry\&. It takes four arguments: the journal context object, a string with the field name to request, plus a pair of pointers to pointer/size variables where the data object and its size shall be stored in\&. The field name should be an entry field name\&. Well\-known field names are listed in
|
|
\fBsystemd.journal-fields\fR(7)\&. The returned data is in a read\-only memory map and is only valid until the next invocation of
|
|
\fBsd_journal_get_data()\fR
|
|
or
|
|
\fBsd_journal_enumerate_data()\fR, or the read pointer is altered\&. Note that the data returned will be prefixed with the field name and \*(Aq=\*(Aq\&. Also note that by default data fields larger than 64K might get truncated to 64K\&. This threshold may be changed and turned off with
|
|
\fBsd_journal_set_data_threshold()\fR
|
|
(see below)\&.
|
|
.PP
|
|
\fBsd_journal_enumerate_data()\fR
|
|
may be used to iterate through all fields of the current entry\&. On each invocation the data for the next field is returned\&. The order of these fields is not defined\&. The data returned is in the same format as with
|
|
\fBsd_journal_get_data()\fR
|
|
and also follows the same life\-time semantics\&.
|
|
.PP
|
|
\fBsd_journal_restart_data()\fR
|
|
resets the data enumeration index to the beginning of the entry\&. The next invocation of
|
|
\fBsd_journal_enumerate_data()\fR
|
|
will return the first field of the entry again\&.
|
|
.PP
|
|
Note that the
|
|
\fBSD_JOURNAL_FOREACH_DATA()\fR
|
|
macro may be used as a handy wrapper around
|
|
\fBsd_journal_restart_data()\fR
|
|
and
|
|
\fBsd_journal_enumerate_data()\fR\&.
|
|
.PP
|
|
Note that these functions will not work before
|
|
\fBsd_journal_next\fR(3)
|
|
(or related call) has been called at least once, in order to position the read pointer at a valid entry\&.
|
|
.PP
|
|
\fBsd_journal_set_data_threshold()\fR
|
|
may be used to change the data field size threshold for data returned by
|
|
\fBsd_journal_get_data()\fR,
|
|
\fBsd_journal_enumerate_data()\fR
|
|
and
|
|
\fBsd_journal_enumerate_unique()\fR\&. This threshold is a hint only: it indicates that the client program is interested only in the initial parts of the data fields, up to the threshold in size \-\- but the library might still return larger data objects\&. That means applications should not rely exclusively on this setting to limit the size of the data fields returned, but need to apply a explicit size limit on the returned data as well\&. This threshold defaults to 64K by default\&. To retrieve the complete data fields this threshold should be turned off by setting it to 0, so that the library always returns the complete data objects\&. It is recommended to set this threshold as low as possible since this relieves the library from having to decompress large compressed data objects in full\&.
|
|
.PP
|
|
\fBsd_journal_get_data_threshold()\fR
|
|
returns the currently configured data field size threshold\&.
|
|
.SH "RETURN VALUE"
|
|
.PP
|
|
\fBsd_journal_get_data()\fR
|
|
returns 0 on success or a negative errno\-style error code\&. If the current entry does not include the specified field, \-ENOENT is returned\&. If
|
|
\fBsd_journal_next\fR(3)
|
|
has not been called at least once, \-EADDRNOTAVAIL is returned\&.
|
|
\fBsd_journal_enumerate_data()\fR
|
|
returns a positive integer if the next field has been read, 0 when no more fields are known, or a negative errno\-style error code\&.
|
|
\fBsd_journal_restart_data()\fR
|
|
returns nothing\&.
|
|
\fBsd_journal_set_data_threshold()\fR
|
|
and
|
|
\fBsd_journal_get_threshold()\fR
|
|
return 0 on success or a negative errno\-style error code\&.
|
|
.SH "NOTES"
|
|
.PP
|
|
The
|
|
\fBsd_journal_get_data()\fR,
|
|
\fBsd_journal_enumerate_data()\fR,
|
|
\fBsd_journal_restart_data()\fR,
|
|
\fBsd_journal_set_data_threshold()\fR
|
|
and
|
|
\fBsd_journal_get_data_threshold()\fR
|
|
interfaces are available as a shared library, which can be compiled and linked to with the
|
|
\fBlibsystemd\fR\ \&\fBpkg-config\fR(1)
|
|
file\&.
|
|
.SH "EXAMPLES"
|
|
.PP
|
|
See
|
|
\fBsd_journal_next\fR(3)
|
|
for a complete example how to use
|
|
\fBsd_journal_get_data()\fR\&.
|
|
.PP
|
|
Use the
|
|
\fBSD_JOURNAL_FOREACH_DATA\fR
|
|
macro to iterate through all fields of the current journal entry:
|
|
.sp
|
|
.if n \{\
|
|
.RS 4
|
|
.\}
|
|
.nf
|
|
\&.\&.\&.
|
|
int print_fields(sd_journal *j) {
|
|
const void *data;
|
|
size_t length;
|
|
SD_JOURNAL_FOREACH_DATA(j, data, length)
|
|
printf("%\&.*s\en", (int) length, data);
|
|
}
|
|
\&.\&.\&.
|
|
.fi
|
|
.if n \{\
|
|
.RE
|
|
.\}
|
|
.SH "SEE ALSO"
|
|
.PP
|
|
\fBsystemd\fR(1),
|
|
\fBsystemd.journal-fields\fR(7),
|
|
\fBsd-journal\fR(3),
|
|
\fBsd_journal_open\fR(3),
|
|
\fBsd_journal_next\fR(3),
|
|
\fBsd_journal_get_realtime_usec\fR(3),
|
|
\fBsd_journal_query_unique\fR(3)
|