|GETSOCKOPT(3P)||POSIX Programmer's Manual||GETSOCKOPT(3P)|
int getsockopt(int socket, int level, int option_name, void *restrict option_value, socklen_t *restrict option_len);
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.
- The socket 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.
- The socket argument does not refer to a socket.
The getsockopt() 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 function.
The following sections are informative.
The Base Definitions volume of POSIX.1‐2017, <sys_socket.h>, <netinet_in.h>
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 .
|2017||IEEE/The Open Group|