sd-daemon(3) — Linux manual page


SD-DAEMON(3)                    sd-daemon                   SD-DAEMON(3)

NAME         top

       SD_NOTICE, SD_INFO, SD_DEBUG - APIs for new-style daemons

SYNOPSIS         top

       #include <systemd/sd-daemon.h>

       pkg-config --cflags --libs libsystemd

DESCRIPTION         top

       sd-daemon.h is part of libsystemd(3) and provides APIs for
       new-style daemons, as implemented by the systemd(1) service

       See sd_listen_fds(3), sd_notify(3), sd_booted(3), sd_is_fifo(3),
       sd_watchdog_enabled(3) for more information about the functions
       implemented. In addition to these functions, a couple of logging
       prefixes are defined as macros:

           #define SD_EMERG   "<0>"  /* system is unusable */
           #define SD_ALERT   "<1>"  /* action must be taken immediately */
           #define SD_CRIT    "<2>"  /* critical conditions */
           #define SD_ERR     "<3>"  /* error conditions */
           #define SD_WARNING "<4>"  /* warning conditions */
           #define SD_NOTICE  "<5>"  /* normal but significant condition */
           #define SD_INFO    "<6>"  /* informational */
           #define SD_DEBUG   "<7>"  /* debug-level messages */

       These prefixes are intended to be used in conjunction with
       stderr-based logging (or stdout-based logging) as implemented by
       systemd. If a systemd service definition file is configured with
       StandardError=journal or StandardError=kmsg (and similar with
       StandardOutput=), these prefixes can be used to encode a log
       level in lines printed. This is similar to the kernel
       printk()-style logging. See klogctl(2) for more information.

       The log levels are identical to syslog(3)'s log level system. To
       use these prefixes simply prefix every line with one of these
       strings. A line that is not prefixed will be logged at the
       default log level SD_INFO.

       Example 1. Hello World

       A daemon may log with the log level NOTICE by issuing this call:

           fprintf(stderr, SD_NOTICE "Hello World!\n");

NOTES         top

       Functions described here are available as a shared library, which
       can be compiled against and linked to with the
       libsystemd pkg-config(1) file.

       The code described here uses getenv(3), which is declared to be
       not multi-thread-safe. This means that the code calling the
       functions described here must not call setenv(3) from a parallel
       thread. It is recommended to only do calls to setenv() from an
       early phase of the program when no other threads have been

SEE ALSO         top

       systemd(1), sd_listen_fds(3), sd_notify(3), sd_booted(3),
       sd_is_fifo(3), sd_watchdog_enabled(3), daemon(7),
       systemd.service(5), systemd.socket(5), fprintf(3), pkg-config(1)

COLOPHON         top

       This page is part of the systemd (systemd system and service
       manager) project.  Information about the project can be found at
       ⟨⟩.  If you have
       a bug report for this manual page, see
       This page was obtained from the project's upstream Git repository
       ⟨⟩ on 2024-06-14.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2024-06-13.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

systemd 257~devel                                           SD-DAEMON(3)

Pages that refer to this page: systemd(1)libsystemd(3)sd_booted(3)sd_is_fifo(3)sd_journal_stream_fd(3)sd_listen_fds(3)sd-login(3)sd_notify(3)sd_watchdog_enabled(3)systemd.exec(5)daemon(7)systemd.directives(7)systemd.index(7)