x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
SD_JOURNAL_STREAM_FD(3) sd_journal_stream_fd SD_JOURNAL_STREAM_FD(3)
NAME
sd_journal_stream_fd - Create log stream file descriptor to the journal
SYNOPSIS
#include <systemd/sd-journal.h>
int sd_journal_stream_fd(const char *identifier, int priority,
int level_prefix);
DESCRIPTION
sd_journal_stream_fd() may be used to create a log stream file
descriptor. Log messages written to this file descriptor as simple
newline-separated text strings are written to the journal. This file
descriptor can be used internally by applications or be made standard
output or standard error of other processes executed.
sd_journal_stream_fd() takes a short program identifier string as first
argument, which will be written to the journal as SYSLOG_IDENTIFIER=
field for each log entry (see systemd.journal-fields(7) for more
information). The second argument shall be the default priority level
for all messages. The priority level is one of LOG_EMERG, LOG_ALERT,
LOG_CRIT, LOG_ERR, LOG_WARNING, LOG_NOTICE, LOG_INFO, LOG_DEBUG, as
defined in syslog.h, see syslog(3) for details. The third argument is a
boolean: if true kernel-style log level prefixes (such as SD_WARNING)
are interpreted, see sd-daemon(3) for more information.
It is recommended that applications log UTF-8 messages only with this
API, but this is not enforced.
Each invocation of sd_journal_stream_fd() allocates a new log stream
file descriptor, that is not shared with prior or later invocations.
The file descriptor is write-only (its reading direction is shut down),
and O_NONBLOCK is turned off initially.
RETURN VALUE
The call returns a valid write-only file descriptor on success or a
negative errno-style error code.
SIGNAL SAFETY
sd_journal_stream_fd() is "async signal safe" in the meaning of signal-
safety(7).
NOTES
All functions listed here are thread-safe and may be called in parallel
from multiple threads.
Functions described here are available as a shared library, which can
be compiled against and linked to with the libsystemd pkg-config(1)
file.
EXAMPLES
Creating a log stream suitable for fprintf(3):
/* SPDX-License-Identifier: MIT-0 */
#include <errno.h>
#include <syslog.h>
#include <stdio.h>
#include <unistd.h>
#include <systemd/sd-journal.h>
#include <systemd/sd-daemon.h>
int main(int argc, char *argv[]) {
int fd;
FILE *log;
fd = sd_journal_stream_fd("test", LOG_INFO, 1);
if (fd < 0) {
errno = -fd;
fprintf(stderr, "Failed to create stream fd: %m\n");
return 1;
}
log = fdopen(fd, "w");
if (!log) {
fprintf(stderr, "Failed to create file object: %m\n");
close(fd);
return 1;
}
fprintf(log, "Hello World!\n");
fprintf(log, SD_WARNING "This is a warning!\n");
fclose(log);
return 0;
}
SEE ALSO
systemd(1), sd-journal(3), sd-daemon(3), sd_journal_print(3),
syslog(3), fprintf(3), systemd.journal-fields(7)
systemd 254 SD_JOURNAL_STREAM_FD(3)
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