sd_is_fifo, sd_is_socket, sd_is_socket_inet, sd_is_socket_unix, sd_is_mq — Check the type of a file descriptor
#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) ; |
sd_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.
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.
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.