GETSOCKOPT
Section: POSIX Programmer's Manual (3P)
Updated: 2013
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PROLOG
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
getsockopt
--- get the socket options
SYNOPSIS
#include <sys/socket.h>
int getsockopt(int socket, int level, int option_name,
void *restrict option_value, socklen_t *restrict option_len);
DESCRIPTION
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.
RETURN VALUE
Upon successful completion,
getsockopt()
shall return 0; otherwise, -1 shall be returned and
errno
set to indicate the error.
ERRORS
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
None.
APPLICATION USAGE
None.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
Section 2.10.16,
Use of Options,
bind(),
close(),
endprotoent(),
setsockopt(),
socket()
The Base Definitions volume of POSIX.1-2008,
<sys_socket.h>,
<netinet_in.h>
COPYRIGHT
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
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
Index
- PROLOG
-
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- EXAMPLES
-
- APPLICATION USAGE
-
- RATIONALE
-
- FUTURE DIRECTIONS
-
- SEE ALSO
-
- COPYRIGHT
-
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