sd-daemon

systemd
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`

## Description

`sd-daemon.h` 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`, `StandardError=syslog` 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.

Hello World

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

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

## See Also

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