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

       Function sd_journal_stream_fd() is thread-safe and may be called from multiple threads.

       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.

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)

systemd 237                                                                              SD_JOURNAL_STREAM_FD(3)