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SD-DAEMON(3) sd-daemon SD-DAEMON(3)
sd-daemon, SD_EMERG, SD_ALERT, SD_CRIT, SD_ERR, SD_WARNING,
SD_NOTICE, SD_INFO, SD_DEBUG - APIs for new-style daemons
#include <systemd/sd-daemon.h>
pkg-config --cflags --libs libsystemd
sd-daemon.h is part of libsystemd(3) and provides APIs for
new-style daemons, as implemented by the systemd(1) service
manager.
See sd_listen_fds(3), sd_notify(3), sd_booted(3), sd_is_fifo(3),
sd_watchdog_enabled(3), and sd_pidfd_get_inode_id(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");
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
started.
systemd(1), sd_listen_fds(3), sd_notify(3), sd_booted(3),
sd_is_fifo(3), sd_watchdog_enabled(3), sd_pidfd_get_inode_id(3),
daemon(7), systemd.service(5), systemd.socket(5), fprintf(3),
pkg-config(1)
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a
bug report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-08-11.) 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
man-pages@man7.org
systemd 258~rc2 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_pidfd_get_inode_id(3), sd_watchdog_enabled(3), systemd.exec(5), daemon(7), systemd.directives(7), systemd.index(7)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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