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 shared library, which can be compiled and linked to with the
       libsystemd-daemonpkg-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 ALSO

       systemd(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)