GETSOCKOPT(3P) POSIX Programmer's Manual GETSOCKOPT(3P)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.
NAMEgetsockopt — get the socket options
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 spec‐
ified 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 indi‐
cate 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 privi‐
leges 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 following sections are informative.
Section 2.10.16, Use of Options, bind(), close(), endprotoent(), set‐
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 Electri‐
cal 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 .
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IEEE/The Open Group 2013 GETSOCKOPT(3P)