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 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. 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 shared library, which can be compiled and linked to with the libsystemd-journal pkg-config1 file. 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; } systemd1, sd-journal3, sd-daemon3, sd_journal_print3, syslog3, fprintf3, systemd.journal-fields7