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

       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.

       getsockopt — get the socket options

       #include <sys/socket.h>

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

       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> and
       described in Section 2.10.16, Use of Options.

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

       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.

              The option is not supported by the protocol.

              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.

              Insufficient resources are available in the system to complete the

       The following sections are informative.





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

       The Base Definitions volume of POSIX.1‐2008, <sys_socket.h>,

       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical
       and Electronics Engineers, Inc and The Open Group.  (This is POSIX.1-2008
       with the 2013 Technical Corrigendum 1 applied.) 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 .

       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 .

IEEE/The Open Group                   2013                    GETSOCKOPT(3POSIX)