SD_IS_FIFO(3) sd_is_fifo SD_IS_FIFO(3)NAME
sd_is_fifo, sd_is_socket, sd_is_socket_inet, sd_is_socket_unix,
sd_is_mq - Check the type of a file descriptor
SYNOPSIS
#include <systemd/sd-daemon.h>
int sd_is_fifo(int fd, const char *path);
int sd_is_socket(int fd, int family, int type, int listening);
int sd_is_socket_inet(int fd, int family, int type, int listening,
uint16_t port);
int sd_is_socket_unix(int fd, int type, int listening,
const char* path, size_t length);
int sd_is_mq(int fd, const char *path);
DESCRIPTIONsd_is_fifo() may be called to check whether the specified file
descriptor refers to a FIFO or pipe. If the path parameter is not NULL,
it is checked whether the FIFO is bound to the specified file system
path.
sd_is_socket() may be called to check whether the specified file
descriptor refers to a socket. If the family parameter is not
AF_UNSPEC, it is checked whether the socket is of the specified family
(AF_UNIX, AF_INET, ...). If the type parameter is not 0, it is checked
whether the socket is of the specified type (SOCK_STREAM, SOCK_DGRAM,
...). If the listening parameter is positive, it is checked whether the
socket is in accepting mode, i.e. listen() has been called for it. If
listening is 0, it is checked whether the socket is not in this mode.
If the parameter is negative, no such check is made. The listening
parameter should only be used for stream sockets and should be set to a
negative value otherwise.
sd_is_socket_inet() is similar to sd_is_socket(), but optionally checks
the IPv4 or IPv6 port number the socket is bound to, unless port is
zero. For this call family must be passed as either AF_UNSPEC, AF_INET,
or AF_INET6.
sd_is_socket_unix() is similar to sd_is_socket() but optionally checks
the AF_UNIX path the socket is bound to, unless the path parameter is
NULL. For normal file system AF_UNIX sockets, set the length parameter
to 0. For Linux abstract namespace sockets, set the length to the size
of the address, including the initial 0 byte, and set the path to the
initial 0 byte of the socket address.
sd_is_mq() may be called to check whether the specified file descriptor
refers to a POSIX message queue. If the path parameter is not NULL, it
is checked whether the message queue is bound to the specified name.
RETURN VALUE
On failure, these calls return a negative errno-style error code. If
the file descriptor is of the specified type and bound to the specified
address, a positive return value is returned, otherwise zero.
NOTES
These functions 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 they can easily be
reimplemented in daemons if it is important to support this interface
without using the reference implementation.
Internally, these function use a combination of fstat() and
getsockname() to check the file descriptor type and where it is bound
to.
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
sd_is_fifo() and the related functions 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-daemon pkg-config(1) file. Alternatively,
applications consuming these APIs may copy the implementation into
their source tree. For more details about the reference implementation
see sd-daemon(3).
These functions continue to work as described, even if
-DDISABLE_SYSTEMD is set during compilation.
SEE ALSOsystemd(1), sd-daemon(3), sd_listen_fds(3), systemd.service(5),
systemd.socket(5)systemd 207SD_IS_FIFO(3)
