sd_journal_stream_fd
systemd
Developer
Lennart
Poettering
lennart@poettering.net
sd_journal_stream_fd
3
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
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 STDOUT/STDERR 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-fields7
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
syslog3
for details. The third argument is a boolean: if true
kernel-style log priority level prefixes (such as
SD_WARNING) are interpreted, see
sd-daemon3
for more information.
It is recommended that applications log UTF-8
messages only with this API, but this is not
enforced.
Return Value
The call returns a valid write-only file descriptor on success or a
negative errno-style error code.
Notes
The sd_journal_stream_fd()
interface is available as shared library, which can
be compiled and linked to with the
libsystemd-journal
pkg-config1
file.
Examples
Creating a log stream suitable for
fprintf3:
#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;
}
See Also
systemd1,
sd-journal3,
sd-daemon3,
sd_journal_print3,
syslog3,
fprintf3,
systemd.journal-fields7