SD-DAEMON(3)sd-daemonSD-DAEMON(3)NAME
sd-daemon, SD_EMERG, SD_ALERT, SD_CRIT, SD_ERR, SD_WARNING, SD_NOTICE,
SD_INFO, SD_DEBUG - Reference implementation of APIs for new-style
daemons
SYNOPSIS
#include <systemd/sd-daemon.h>
pkg-config --cflags --libs libsystemd-daemon
DESCRIPTION
sd-daemon.c and sd-daemon.h provide a reference implementation of
various APIs for new-style daemons, as implemented by the systemd(1)
init system.
See sd_listen_fds(3), sd_notify(3), sd_booted(3), sd_is_fifo(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 as implemented by systemd. If a systemd service definition file
is configured with StandardError=syslog or StandardError=kmsg, 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
These interfaces are provided by the reference implementation of APIs
for new-style daemons and distributed with the systemd package. The
algorithms they implement are simple, and can easily be reimplemented
in daemons if it is important to support this interface without using
the reference implementation. See the respective function man pages for
details.
In addition, for details about the algorithms, check the liberally
licensed reference implementation sources:
http://cgit.freedesktop.org/systemd/systemd/plain/src/libsystemd-daemon/sd-daemon.c
and
http://cgit.freedesktop.org/systemd/systemd/plain/src/systemd/sd-daemon.h
These APIs are implemented in the reference implementation's
sd-daemon.c and sd-daemon.h files. These interfaces are available as a
shared library, which can be compiled and linked to with the
libsystemd-daemon pkg-config(1) file. Alternatively, applications
consuming these APIs may copy the implementation into their source
tree, either verbatim or in excerpts.
The functions directly related to new-style daemons become NOPs when
-DDISABLE_SYSTEMD is set during compilation and the reference
implementation is used as drop-in files. In addition, if sd-daemon.c is
compiled on non-Linux systems they become NOPs.
SEE ALSOsystemd(1), sd_listen_fds(3), sd_notify(3), sd_booted(3),
sd_is_fifo(3), daemon(7), systemd.service(5), systemd.socket(5),
fprintf(3), sd-readahead(3), pkg-config(1)systemd 208SD-DAEMON(3)