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diff --git a/man/sd_listen_fds.xml b/man/sd_listen_fds.xml
index c9b399701..437774563 100644
--- a/man/sd_listen_fds.xml
+++ b/man/sd_listen_fds.xml
@@ -21,7 +21,8 @@
along with systemd; If not, see .
-->
-
+
sd_listen_fds
@@ -70,10 +71,10 @@
activation logic.
If the unset_environment
- parameter is non-zero
+ parameter is non-zero,
sd_listen_fds() will unset the
- $LISTEN_FDS/$LISTEN_PID
- environment variables before returning (regardless
+ $LISTEN_FDS and $LISTEN_PID
+ environment variables before returning (regardless of
whether the function call itself succeeded or
not). Further calls to
sd_listen_fds() will then fail,
@@ -82,17 +83,18 @@
If a daemon receives more than one file
descriptor, they will be passed in the same order as
- configured in the systemd socket definition
- file. Nonetheless it is recommended to verify the
- correct socket types before using them. To simplify
- this checking the functions
+ configured in the systemd socket unit file (see
+ systemd.socket5
+ for details). Nonetheless, it is recommended to verify
+ the correct socket types before using them. To
+ simplify this checking, the functions
sd_is_fifo3,
sd_is_socket3,
sd_is_socket_inet3,
sd_is_socket_unix3
- are provided. In order to maximize flexibility it is
+ are provided. In order to maximize flexibility, it is
recommended to make these checks as loose as possible
- without allowing incorrect setups. i.e. often the
+ without allowing incorrect setups. i.e. often, the
actual port number a socket is bound to matters little
for the service to work, hence it should not be
verified. On the other hand, whether a socket is a
@@ -102,6 +104,16 @@
This function call will set the FD_CLOEXEC flag
for all passed file descriptors to avoid further
inheritance to children of the calling process.
+
+ If multiple socket units activate the same
+ service the order of the file descriptors passed to
+ its main process is undefined. If additional file
+ descriptors have been passed to the service manager
+ using
+ sd_pid_notify_with_fds3's
+ FDSTORE=1 messages, these file
+ descriptors are passed last, in arbitrary order, and
+ with duplicates removed.
@@ -112,7 +124,7 @@
$LISTEN_FDS/$LISTEN_PID
was not set or was not correctly set for this daemon and
hence no file descriptors were received, 0 is
- returned. Otherwise the number of file descriptors
+ returned. Otherwise, the number of file descriptors
passed is returned. The application may find them
starting with file descriptor SD_LISTEN_FDS_START,
i.e. file descriptor 3.
@@ -121,47 +133,17 @@
Notes
- This function is provided by the reference
- implementation of APIs for new-style daemons and
- distributed with the systemd package. The algorithm it
- implements is simple, and can easily be reimplemented
- in daemons if it is important to support this
- interface without using the reference
- implementation.
+
Internally, this function checks whether the
$LISTEN_PID environment variable
equals the daemon PID. If not, it returns
- immediately. Otherwise it parses the number passed in
+ immediately. Otherwise, it parses the number passed in
the $LISTEN_FDS environment
variable, then sets the FD_CLOEXEC flag for the parsed
number of file descriptors starting from
- SD_LISTEN_FDS_START. Finally it returns the parsed
+ SD_LISTEN_FDS_START. Finally, it returns the parsed
number.
-
- For details about the algorithm check the
- liberally licensed reference implementation sources:
-
- and
-
- sd_listen_fds() is
- 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-daemon pkg-config1
- file. Alternatively, applications consuming these APIs
- may copy the implementation into their source
- tree. For more details about the reference
- implementation see
- sd-daemon3.
-
- If the reference implementation is used as
- drop-in files and -DDISABLE_SYSTEMD is set during
- compilation this function will always return 0 and
- otherwise become a NOP.