Section: POSIX Programmer's Manual (3P)
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.
--- get the socket options
int getsockopt(int socket, int level, int option_name,
void *restrict option_value, socklen_t *restrict option_len);
function manipulates options associated with a socket.
function shall retrieve the value for the option specified by the
argument for the socket specified by the
argument. If the size of the option value is greater than
the value stored in the object pointed to by the
argument shall be silently truncated. Otherwise, the object pointed to
argument shall be modified to indicate the actual length of the value.
argument specifies the protocol level at which the option resides. To
retrieve options at the socket level, specify the
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
to IPPROTO_TCP as defined in the
The socket in use may require the process to have appropriate
privileges to use the
argument specifies a single option to be retrieved. It can be one of
the socket-level options defined in
and described in
Section 2.10.16, Use of Options.
Upon successful completion,
shall return 0; otherwise, -1 shall be returned and
set to indicate the error.
function shall fail if:
argument is not a valid file descriptor.
The specified option is invalid at the specified socket level.
The option is not supported by the protocol.
argument does not refer to a socket.
function may fail if:
The calling process does not have appropriate privileges.
The socket has been shut down.
Insufficient resources are available in the system to complete the
The following sections are informative.
, Use of Options,
The Base Definitions volume of POSIX.1-2017,
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
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