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 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-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 mesages 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-config(1) file.

EXAMPLES

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;
    }

SEE ALSO

systemd(1), sd-journal(3), sd-daemon(3), sd_journal_print(3), syslog(3), fprintf(3), systemd.journal-fields(7)