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/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
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#ifndef foosddaemonhfoo
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#define foosddaemonhfoo
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Copyright 2010 Lennart Poettering
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Permission is hereby granted, free of charge, to any person
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obtaining a copy of this software and associated documentation files
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(the "Software"), to deal in the Software without restriction,
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including without limitation the rights to use, copy, modify, merge,
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publish, distribute, sublicense, and/or sell copies of the Software,
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and to permit persons to whom the Software is furnished to do so,
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subject to the following conditions:
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The above copyright notice and this permission notice shall be
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included in all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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#include <sys/types.h>
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Reference implementation of a few systemd related interfaces for
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writing daemons. These interfaces are trivial to implement. To
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simplify porting we provide this reference implementation.
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Applications are welcome to reimplement the algorithms described
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here if they do not want to include these two source files.
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The following functionality is provided:
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- Support for logging with log levels on stderr
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- File descriptor passing for socket-based activation
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- Daemon startup and status notification
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- Detection of systemd boots
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You may compile this with -DDISABLE_SYSTEMD to disable systemd
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support. This makes all those calls NOPs that are directly related to
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systemd (i.e. only sd_is_xxx() will stay useful).
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Since this is drop-in code we don't want any of our symbols to be
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exported in any case. Hence we declare hidden visibility for all of
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You may find an up-to-date version of these source files online:
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http://cgit.freedesktop.org/systemd/plain/src/sd-daemon.h
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http://cgit.freedesktop.org/systemd/plain/src/sd-daemon.c
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This should compile on non-Linux systems, too, but with the
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exception of the sd_is_xxx() calls all functions will become NOPs.
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See sd-daemon(7) for more information.
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#ifndef _sd_printf_attr_
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#define _sd_printf_attr_(a,b) __attribute__ ((format (printf, a, b)))
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#define _sd_printf_attr_(a,b)
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Log levels for usage on stderr:
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fprintf(stderr, SD_NOTICE "Hello World!\n");
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This is similar to printk() usage in the kernel.
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#define SD_EMERG "<0>" /* system is unusable */
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#define SD_ALERT "<1>" /* action must be taken immediately */
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#define SD_CRIT "<2>" /* critical conditions */
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#define SD_ERR "<3>" /* error conditions */
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#define SD_WARNING "<4>" /* warning conditions */
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#define SD_NOTICE "<5>" /* normal but significant condition */
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#define SD_INFO "<6>" /* informational */
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#define SD_DEBUG "<7>" /* debug-level messages */
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/* The first passed file descriptor is fd 3 */
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#define SD_LISTEN_FDS_START 3
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Returns how many file descriptors have been passed, or a negative
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errno code on failure. Optionally, removes the $LISTEN_FDS and
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$LISTEN_PID file descriptors from the environment (recommended, but
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problematic in threaded environments). If r is the return value of
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this function you'll find the file descriptors passed as fds
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SD_LISTEN_FDS_START to SD_LISTEN_FDS_START+r-1. Returns a negative
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errno style error code on failure. This function call ensures that
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the FD_CLOEXEC flag is set for the passed file descriptors, to make
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sure they are not passed on to child processes. If FD_CLOEXEC shall
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not be set, the caller needs to unset it after this call for all file
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descriptors that are used.
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See sd_listen_fds(3) for more information.
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int sd_listen_fds(int unset_environment);
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Helper call for identifying a passed file descriptor. Returns 1 if
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the file descriptor is a FIFO in the file system stored under the
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specified path, 0 otherwise. If path is NULL a path name check will
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not be done and the call only verifies if the file descriptor
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refers to a FIFO. Returns a negative errno style error code on
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See sd_is_fifo(3) for more information.
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int sd_is_fifo(int fd, const char *path);
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Helper call for identifying a passed file descriptor. Returns 1 if
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the file descriptor is a special character device on the file
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system stored under the specified path, 0 otherwise.
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If path is NULL a path name check will not be done and the call
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only verifies if the file descriptor refers to a special character.
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Returns a negative errno style error code on failure.
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See sd_is_special(3) for more information.
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int sd_is_special(int fd, const char *path);
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Helper call for identifying a passed file descriptor. Returns 1 if
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the file descriptor is a socket of the specified family (AF_INET,
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...) and type (SOCK_DGRAM, SOCK_STREAM, ...), 0 otherwise. If
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family is 0 a socket family check will not be done. If type is 0 a
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socket type check will not be done and the call only verifies if
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the file descriptor refers to a socket. If listening is > 0 it is
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verified that the socket is in listening mode. (i.e. listen() has
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been called) If listening is == 0 it is verified that the socket is
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not in listening mode. If listening is < 0 no listening mode check
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is done. Returns a negative errno style error code on failure.
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See sd_is_socket(3) for more information.
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int sd_is_socket(int fd, int family, int type, int listening);
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Helper call for identifying a passed file descriptor. Returns 1 if
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the file descriptor is an Internet socket, of the specified family
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(either AF_INET or AF_INET6) and the specified type (SOCK_DGRAM,
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SOCK_STREAM, ...), 0 otherwise. If version is 0 a protocol version
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check is not done. If type is 0 a socket type check will not be
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done. If port is 0 a socket port check will not be done. The
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listening flag is used the same way as in sd_is_socket(). Returns a
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negative errno style error code on failure.
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See sd_is_socket_inet(3) for more information.
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int sd_is_socket_inet(int fd, int family, int type, int listening, uint16_t port);
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Helper call for identifying a passed file descriptor. Returns 1 if
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the file descriptor is an AF_UNIX socket of the specified type
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(SOCK_DGRAM, SOCK_STREAM, ...) and path, 0 otherwise. If type is 0
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a socket type check will not be done. If path is NULL a socket path
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check will not be done. For normal AF_UNIX sockets set length to
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0. For abstract namespace sockets set length to the length of the
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socket name (including the initial 0 byte), and pass the full
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socket path in path (including the initial 0 byte). The listening
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flag is used the same way as in sd_is_socket(). Returns a negative
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errno style error code on failure.
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See sd_is_socket_unix(3) for more information.
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int sd_is_socket_unix(int fd, int type, int listening, const char *path, size_t length);
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Helper call for identifying a passed file descriptor. Returns 1 if
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the file descriptor is a POSIX Message Queue of the specified name,
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0 otherwise. If path is NULL a message queue name check is not
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done. Returns a negative errno style error code on failure.
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int sd_is_mq(int fd, const char *path);
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Informs systemd about changed daemon state. This takes a number of
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newline separated environment-style variable assignments in a
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string. The following variables are known:
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READY=1 Tells systemd that daemon startup is finished (only
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relevant for services of Type=notify). The passed
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argument is a boolean "1" or "0". Since there is
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little value in signaling non-readiness the only
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value daemons should send is "READY=1".
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STATUS=... Passes a single-line status string back to systemd
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that describes the daemon state. This is free-from
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and can be used for various purposes: general state
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feedback, fsck-like programs could pass completion
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percentages and failing programs could pass a human
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readable error message. Example: "STATUS=Completed
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66% of file system check..."
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ERRNO=... If a daemon fails, the errno-style error code,
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formatted as string. Example: "ERRNO=2" for ENOENT.
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BUSERROR=... If a daemon fails, the D-Bus error-style error
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code. Example: "BUSERROR=org.freedesktop.DBus.Error.TimedOut"
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MAINPID=... The main pid of a daemon, in case systemd did not
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fork off the process itself. Example: "MAINPID=4711"
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Daemons can choose to send additional variables. However, it is
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recommended to prefix variable names not listed above with X_.
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Returns a negative errno-style error code on failure. Returns > 0
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if systemd could be notified, 0 if it couldn't possibly because
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systemd is not running.
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Example: When a daemon finished starting up, it could issue this
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call to notify systemd about it:
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sd_notify(0, "READY=1");
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See sd_notifyf() for more complete examples.
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See sd_notify(3) for more information.
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int sd_notify(int unset_environment, const char *state);
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Similar to sd_notify() but takes a format string.
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Example 1: A daemon could send the following after initialization:
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sd_notifyf(0, "READY=1\n"
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"STATUS=Processing requests...\n"
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(unsigned long) getpid());
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Example 2: A daemon could send the following shortly before
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sd_notifyf(0, "STATUS=Failed to start up: %s\n"
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See sd_notifyf(3) for more information.
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int sd_notifyf(int unset_environment, const char *format, ...) _sd_printf_attr_(2,3);
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Returns > 0 if the system was booted with systemd. Returns < 0 on
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error. Returns 0 if the system was not booted with systemd. Note
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that all of the functions above handle non-systemd boots just
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fine. You should NOT protect them with a call to this function. Also
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note that this function checks whether the system, not the user
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session is controlled by systemd. However the functions above work
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for both user and system services.
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See sd_booted(3) for more information.
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src/sd-daemon.h
