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)