NAME

       sd_is_fifo, sd_is_socket, sd_is_socket_inet, sd_is_socket_unix, sd_is_socket_sockaddr,
       sd_is_mq, sd_is_special - 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_sockaddr(int fd, int type, const struct sockaddr *addr,
                                 unsigned addr_len, int listening);

       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);

       int sd_is_special(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_sockaddr() is similar to sd_is_socket_inet(), but checks if the socket is
       bound to the address specified by addr. The family specified by addr must be either
       AF_INET or AF_INET6 and addr_len must be large enough for that family. If addr specifies a
       non-zero port, it is also checked if the socket is bound to this port. In addition, for
       IPv6, if addr specifies non-zero sin6_flowinfo or sin6_scope_id, it is checked if the
       socket has the same values.

       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.

       sd_is_special() may be called to check whether the specified file descriptor refers to a
       special file. If the path parameter is not NULL, it is checked whether the file descriptor
       is bound to the specified filename. Special files in this context are character device
       nodes and files in /proc or /sys.

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 APIs are implemented as a shared library, which can be compiled and linked to with
       the libsystemd pkg-config(1) file.

       Internally, these function use a combination of fstat() and getsockname() to check the
       file descriptor type and where it is bound to.

SEE ALSO

       systemd(1), sd-daemon(3), sd_listen_fds(3), systemd.service(5), systemd.socket(5), ip(7),
       ipv6(7), unix(7), fifo(7), mq_overview(7), socket(7).