trusty (3) sd_is_socket_inet.3.gz
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);
DESCRIPTION
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 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 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-daemonpkg-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 ALSO
systemd(1), sd-daemon(3), sd_listen_fds(3), systemd.service(5), systemd.socket(5)