getsockopt(3p) — Linux manual page

GETSOCKOPT(3P)          POSIX Programmer's Manual         GETSOCKOPT(3P)

PROLOG         top

       This manual page is part of the POSIX Programmer's Manual.  The
       Linux implementation of this interface may differ (consult the
       corresponding Linux manual page for details of Linux behavior),
       or the interface may not be implemented on Linux.

NAME         top

       getsockopt — get the socket options

SYNOPSIS         top

       #include <sys/socket.h>

       int getsockopt(int socket, int level, int option_name,
           void *restrict option_value, socklen_t *restrict option_len);

DESCRIPTION         top

       The getsockopt() function manipulates options associated with a
       socket.

       The getsockopt() function shall retrieve the value for the option
       specified by the option_name argument for the socket specified by
       the socket argument. If the size of the option value is greater
       than option_len, the value stored in the object pointed to by the
       option_value argument shall be silently truncated. Otherwise, the
       object pointed to by the option_len argument shall be modified to
       indicate the actual length of the value.

       The level argument specifies the protocol level at which the
       option resides. To retrieve options at the socket level, specify
       the level argument as SOL_SOCKET. To retrieve options at other
       levels, supply the appropriate level identifier for the protocol
       controlling the option.  For example, to indicate that an option
       is interpreted by the TCP (Transmission Control Protocol), set
       level to IPPROTO_TCP as defined in the <netinet/in.h> header.

       The socket in use may require the process to have appropriate
       privileges to use the getsockopt() function.

       The option_name argument specifies a single option to be
       retrieved. It can be one of the socket-level options defined in
       sys_socket.h(0p) and described in Section 2.10.16, Use of
       Options.

RETURN VALUE         top

       Upon successful completion, getsockopt() shall return 0;
       otherwise, -1 shall be returned and errno set to indicate the
       error.

ERRORS         top

       The getsockopt() function shall fail if:

       EBADF  The socket argument is not a valid file descriptor.

       EINVAL The specified option is invalid at the specified socket
              level.

       ENOPROTOOPT
              The option is not supported by the protocol.

       ENOTSOCK
              The socket argument does not refer to a socket.

       The getsockopt() function may fail if:

       EACCES The calling process does not have appropriate privileges.

       EINVAL The socket has been shut down.

       ENOBUFS
              Insufficient resources are available in the system to
              complete the function.

       The following sections are informative.

EXAMPLES         top

       None.

APPLICATION USAGE         top

       None.

RATIONALE         top

       None.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       Section 2.10.16, Use of Options, bind(3p), close(3p),
       endprotoent(3p), setsockopt(3p), socket(3p)

       The Base Definitions volume of POSIX.1‐2017, sys_socket.h(0p),
       netinet_in.h(0p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 by the Institute of Electrical and Electronics
       Engineers, Inc and The Open Group.  In the event of any
       discrepancy between this version and the original IEEE and The
       Open Group Standard, the original IEEE and The Open Group
       Standard is the referee document. The original Standard can be
       obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page
       are most likely to have been introduced during the conversion of
       the source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group               2017                    GETSOCKOPT(3P)

Pages that refer to this page: netinet_in.h(0p),  netinet_tcp.h(0p),  sys_socket.h(0p),  if_freenameindex(3p),  if_indextoname(3p),  if_nameindex(3p),  if_nametoindex(3p),  send(3p),  sendmsg(3p),  sendto(3p),  setsockopt(3p),  shutdown(3p),  socket(3p)

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