1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
6 Copyright 2010 Lennart Poettering
8 Permission is hereby granted, free of charge, to any person
9 obtaining a copy of this software and associated documentation files
10 (the "Software"), to deal in the Software without restriction,
11 including without limitation the rights to use, copy, modify, merge,
12 publish, distribute, sublicense, and/or sell copies of the Software,
13 and to permit persons to whom the Software is furnished to do so,
14 subject to the following conditions:
16 The above copyright notice and this permission notice shall be
17 included in all copies or substantial portions of the Software.
19 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
20 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
21 MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
22 NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
23 BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
24 ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
25 CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
29 #include <sys/types.h>
37 Reference implementation of a few systemd related interfaces for
38 writing daemons. These interfaces are trivial to implement. To
39 simplify porting we provide this reference implementation.
40 Applications are welcome to reimplement the algorithms described
41 here if they do not want to include these two source files.
43 The following functionality is provided:
45 - Support for logging with log levels on stderr
46 - File descriptor passing for socket-based activation
47 - Daemon startup and status notification
48 - Detection of systemd boots
50 You may compile this with -DDISABLE_SYSTEMD to disable systemd
51 support. This makes all those calls NOPs that are directly related to
52 systemd (i.e. only sd_is_xxx() will stay useful).
54 Since this is drop-in code we don't want any of our symbols to be
55 exported in any case. Hence we declare hidden visibility for all of
58 You may find an up-to-date version of these source files online:
60 https://cgit.freedesktop.org/systemd/plain/src/sd-daemon.h
61 https://cgit.freedesktop.org/systemd/plain/src/sd-daemon.c
63 This should compile on non-Linux systems, too, but with the
64 exception of the sd_is_xxx() calls all functions will become NOPs.
66 See sd-daemon(7) for more information.
69 #ifndef _sd_printf_attr_
71 #define _sd_printf_attr_(a, b) __attribute__((format(printf, a, b)))
73 #define _sd_printf_attr_(a, b)
78 #if (__GNUC__ >= 4) && !defined(SD_EXPORT_SYMBOLS)
79 #define _sd_hidden_ __attribute__((visibility("hidden")))
86 Log levels for usage on stderr:
88 fprintf(stderr, SD_NOTICE "Hello World!\n");
90 This is similar to printk() usage in the kernel.
92 #define SD_EMERG "<0>" /* system is unusable */
93 #define SD_ALERT "<1>" /* action must be taken immediately */
94 #define SD_CRIT "<2>" /* critical conditions */
95 #define SD_ERR "<3>" /* error conditions */
96 #define SD_WARNING "<4>" /* warning conditions */
97 #define SD_NOTICE "<5>" /* normal but significant condition */
98 #define SD_INFO "<6>" /* informational */
99 #define SD_DEBUG "<7>" /* debug-level messages */
101 /* The first passed file descriptor is fd 3 */
102 #define SD_LISTEN_FDS_START 3
105 Returns how many file descriptors have been passed, or a negative
106 errno code on failure. Optionally, removes the $LISTEN_FDS and
107 $LISTEN_PID file descriptors from the environment (recommended, but
108 problematic in threaded environments). If r is the return value of
109 this function you'll find the file descriptors passed as fds
110 SD_LISTEN_FDS_START to SD_LISTEN_FDS_START+r-1. Returns a negative
111 errno style error code on failure. This function call ensures that
112 the FD_CLOEXEC flag is set for the passed file descriptors, to make
113 sure they are not passed on to child processes. If FD_CLOEXEC shall
114 not be set, the caller needs to unset it after this call for all file
115 descriptors that are used.
117 See sd_listen_fds(3) for more information.
119 int sd_listen_fds(int unset_environment) _sd_hidden_;
122 Helper call for identifying a passed file descriptor. Returns 1 if
123 the file descriptor is a FIFO in the file system stored under the
124 specified path, 0 otherwise. If path is NULL a path name check will
125 not be done and the call only verifies if the file descriptor
126 refers to a FIFO. Returns a negative errno style error code on
129 See sd_is_fifo(3) for more information.
131 int sd_is_fifo(int fd, const char *path) _sd_hidden_;
134 Helper call for identifying a passed file descriptor. Returns 1 if
135 the file descriptor is a socket of the specified family (AF_INET,
136 ...) and type (SOCK_DGRAM, SOCK_STREAM, ...), 0 otherwise. If
137 family is 0 a socket family check will not be done. If type is 0 a
138 socket type check will not be done and the call only verifies if
139 the file descriptor refers to a socket. If listening is > 0 it is
140 verified that the socket is in listening mode. (i.e. listen() has
141 been called) If listening is == 0 it is verified that the socket is
142 not in listening mode. If listening is < 0 no listening mode check
143 is done. Returns a negative errno style error code on failure.
145 See sd_is_socket(3) for more information.
147 int sd_is_socket(int fd, int family, int type, int listening) _sd_hidden_;
150 Helper call for identifying a passed file descriptor. Returns 1 if
151 the file descriptor is an Internet socket, of the specified family
152 (either AF_INET or AF_INET6) and the specified type (SOCK_DGRAM,
153 SOCK_STREAM, ...), 0 otherwise. If version is 0 a protocol version
154 check is not done. If type is 0 a socket type check will not be
155 done. If port is 0 a socket port check will not be done. The
156 listening flag is used the same way as in sd_is_socket(). Returns a
157 negative errno style error code on failure.
159 See sd_is_socket_inet(3) for more information.
161 int sd_is_socket_inet(int fd, int family, int type, int listening, uint16_t port) _sd_hidden_;
164 Helper call for identifying a passed file descriptor. Returns 1 if
165 the file descriptor is an AF_UNIX socket of the specified type
166 (SOCK_DGRAM, SOCK_STREAM, ...) and path, 0 otherwise. If type is 0
167 a socket type check will not be done. If path is NULL a socket path
168 check will not be done. For normal AF_UNIX sockets set length to
169 0. For abstract namespace sockets set length to the length of the
170 socket name (including the initial 0 byte), and pass the full
171 socket path in path (including the initial 0 byte). The listening
172 flag is used the same way as in sd_is_socket(). Returns a negative
173 errno style error code on failure.
175 See sd_is_socket_unix(3) for more information.
177 int sd_is_socket_unix(int fd, int type, int listening, const char *path, size_t length) _sd_hidden_;
180 Informs systemd about changed daemon state. This takes a number of
181 newline separated environment-style variable assignments in a
182 string. The following variables are known:
184 READY=1 Tells systemd that daemon startup is finished (only
185 relevant for services of Type=notify). The passed
186 argument is a boolean "1" or "0". Since there is
187 little value in signaling non-readiness the only
188 value daemons should send is "READY=1".
190 STATUS=... Passes a single-line status string back to systemd
191 that describes the daemon state. This is free-from
192 and can be used for various purposes: general state
193 feedback, fsck-like programs could pass completion
194 percentages and failing programs could pass a human
195 readable error message. Example: "STATUS=Completed
196 66% of file system check..."
198 ERRNO=... If a daemon fails, the errno-style error code,
199 formatted as string. Example: "ERRNO=2" for ENOENT.
201 BUSERROR=... If a daemon fails, the D-Bus error-style error
202 code. Example: "BUSERROR=org.freedesktop.DBus.Error.TimedOut"
204 MAINPID=... The main pid of a daemon, in case systemd did not
205 fork off the process itself. Example: "MAINPID=4711"
207 Daemons can choose to send additional variables. However, it is
208 recommended to prefix variable names not listed above with X_.
210 Returns a negative errno-style error code on failure. Returns > 0
211 if systemd could be notified, 0 if it couldn't possibly because
212 systemd is not running.
214 Example: When a daemon finished starting up, it could issue this
215 call to notify systemd about it:
217 sd_notify(0, "READY=1");
219 See sd_notifyf() for more complete examples.
221 See sd_notify(3) for more information.
223 int sd_notify(int unset_environment, const char *state) _sd_hidden_;
226 Similar to sd_notify() but takes a format string.
228 Example 1: A daemon could send the following after initialization:
230 sd_notifyf(0, "READY=1\n"
231 "STATUS=Processing requests...\n"
233 (unsigned long) getpid());
235 Example 2: A daemon could send the following shortly before
238 sd_notifyf(0, "STATUS=Failed to start up: %s\n"
243 See sd_notifyf(3) for more information.
245 int sd_notifyf(int unset_environment, const char *format, ...) _sd_printf_attr_(2, 3) _sd_hidden_;
248 Returns > 0 if the system was booted with systemd. Returns < 0 on
249 error. Returns 0 if the system was not booted with systemd. Note
250 that all of the functions above handle non-systemd boots just
251 fine. You should NOT protect them with a call to this function. Also
252 note that this function checks whether the system, not the user
253 session is controlled by systemd. However the functions above work
254 for both user and system services.
256 See sd_booted(3) for more information.
258 int sd_booted(void) _sd_hidden_;