sd-daemon(3) — Chainguard OS Manuals

SD-DAEMON(3)

sd-daemon

SD-DAEMON(3)

.SH "NAME" sd-daemon, SD_EMERG, SD_ALERT, SD_CRIT, SD_ERR, SD_WARNING, SD_NOTICE, SD_INFO, SD_DEBUG - APIs for new-style daemons

.SH "SYNOPSIS"

#include <systemd/sd-daemon.h>

.HP 912u

pkg-config --cflags --libs libsystemd

.SH "DESCRIPTION"

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

.PP 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 */

.PP 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.

.PP 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.

.PP Example 1. Hello World

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

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

.SH "NOTES"

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

.PP 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 262.2