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sd_is_fifo(3) — Linux manual page

SD_IS_FIFO(3)                   sd_is_fifoSD_IS_FIFO(3)

NAME        top

       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        top

#include <systemd/sd-daemon.h>int sd_is_fifo(intfd, const char *path);int sd_is_socket(intfd, intfamily, inttype, intlistening);int sd_is_socket_inet(intfd, intfamily, inttype, intlistening,uint16_tport);int sd_is_socket_sockaddr(intfd, inttype,const struct sockaddr *addr,unsignedaddr_len, intlistening);int sd_is_socket_unix(intfd, inttype, intlistening,const char *path, size_tlength);int sd_is_mq(intfd, const char *path);int sd_is_special(intfd, const char *path);

DESCRIPTION        top

sd_is_fifo()may be called to check whether the specified file       descriptor refers to a FIFO or pipe. If thepath parameter is notNULL, 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 thefamily parameter is notAF_UNSPEC, it is checked whether the socket is of the specified       family (AF_UNIX,AF_INET, ...). If thetype parameter is not 0, it       is checked whether the socket is of the specified type       (SOCK_STREAM,SOCK_DGRAM, ...). If thelistening parameter is       positive, it is checked whether the socket is in accepting mode,       i.e.listen()has been called for it. Iflistening is 0, it is       checked whether the socket is not in this mode. If the parameter       is negative, no such check is made. Thelistening parameter should       only be used for stream sockets and should be set to a negative       value otherwise.sd_is_socket_inet()is similar tosd_is_socket(), but optionally       checks the IPv4 or IPv6 port number the socket is bound to, unlessport is zero. For this callfamily must be passed as eitherAF_UNSPEC,AF_INET, orAF_INET6.sd_is_socket_sockaddr()is similar tosd_is_socket_inet(), but       checks if the socket is bound to the address specified byaddr.       Thefamily specified byaddr must be eitherAF_INETorAF_INET6       andaddr_len must be large enough for that family. Ifaddr       specifies a non-zero port, it is also checked if the socket is       bound to this port. In addition, for IPv6, ifaddr specifies       non-zerosin6_flowinfo orsin6_scope_id, it is checked if the       socket has the same values.sd_is_socket_unix()is similar tosd_is_socket()but optionally       checks theAF_UNIXpath the socket is bound to, unless thepath       parameter isNULL. For normal file systemAF_UNIXsockets, set thelength parameter to 0. For Linux abstract namespace sockets, set       thelength to the size of the address, including the initial 0       byte, and set thepath 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 thepath parameter       is notNULL, 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 thepath parameter is notNULL, 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        top

       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        top

       Functions described here are available as a shared library, which       can be compiled against and linked to with thelibsystemd pkg-config(1) file.       Internally, these functions use a combination offstat(2) andgetsockname(2) to check the file descriptor type and where it is       bound to.

HISTORY        top

sd_is_special()was added in version 209.sd_is_socket_sockaddr()was added in version 233.

SEE ALSO        top

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).

COLOPHON        top

       This page is part of thesystemd (systemd system and service       manager) project.  Information about the project can be found at       ⟨http://www.freedesktop.org/wiki/Software/systemd⟩.  If you have a       bug report for this manual page, see       ⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.       This page was obtained from the project's upstream Git repository       ⟨https://github.com/systemd/systemd.git⟩ on 2025-08-11.  (At that       time, the date of the most recent commit that was found in the       repository was 2025-08-11.)  If you discover any rendering       problems in this HTML version of the page, or you believe there is       a better or more up-to-date source for the page, or you have       corrections or improvements to the information in this COLOPHON       (which isnot part of the original manual page), send a mail to       man-pages@man7.orgsystemd 258~rc2SD_IS_FIFO(3)

Pages that refer to this page:sd-daemon(3), sd_listen_fds(3), systemd.directives(7), systemd.index(7)

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