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 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.

EXAMPLES

None.

APPLICATION USAGE

None.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

2.10.16 Use of Options, bind, close, endprotoent, setsockopt, socket

XBD <sys/socket.h>, <netinet/in.h>

CHANGE HISTORY

First released in Issue 6. Derived from the XNS, Issue 5.2 specification.

The restrict keyword is added to the getsockopt() prototype for alignment with the ISO/IEC 9899:1999 standard.

IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/47 is applied, updating the description of SO_LINGER in the DESCRIPTION so that it blocks the calling thread rather than the process.

Issue 7

Austin Group Interpretation 1003.1-2001 #158 is applied, removing text relating to socket options that is now in 2.10.16 Use of Options.