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) 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.