sd_journal_stream_fd — Create log stream file descriptor to the journal
#include <systemd/sd-journal.h>
int sd_journal_stream_fd( | const char *identifier, |
| int priority, | |
int level_prefix); |
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 priority 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.
The call returns a valid write-only file descriptor on success or a negative errno-style error code.
The sd_journal_stream_fd()
interface is available as a shared library, which can
be compiled and linked to with the
libsystemd pkg-config(1)
file.
Creating a log stream suitable for fprintf(3):
#include <syslog.h>
#include <stdio.h>
#include <string.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) {
fprintf(stderr, "Failed to create stream fd: %s\n", strerror(-fd));
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;
}