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.
The getsockopt() function manipulates options associated with a
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.
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 following sections are informative.
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 http://www.unix.org/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
IEEE/The Open Group 2013 GETSOCKOPT(3P)