Originální popis anglicky:
getsockopt, setsockopt - get and set options on sockets
Návod, kniha: Linux Programmer's Manual
#include <sys/types.h>
#include <sys/socket.h>
int getsockopt(int s, int level, int
optname, void *optval, socklen_t
*optlen);
int setsockopt(int s, int level, int
optname, const void *optval, socklen_t
optlen);
Getsockopt and
setsockopt manipulate the
options associated
with a socket. Options may exist at multiple protocol levels; they are always
present at the uppermost
socket level.
When manipulating socket options the level at which the option resides and the
name of the option must be specified. To manipulate options at the socket
level,
level is specified as
SOL_SOCKET. To manipulate options
at any other level the protocol number of the appropriate protocol controlling
the option is supplied. For example, to indicate that an option is to be
interpreted by the
TCP protocol,
level should be set to the
protocol number of
TCP; see
getprotoent(3).
The parameters
optval and
optlen are used to access option values
for
setsockopt. For
getsockopt they identify a buffer in which
the value for the requested option(s) are to be returned. For
getsockopt,
optlen is a value-result parameter, initially
containing the size of the buffer pointed to by
optval, and modified on
return to indicate the actual size of the value returned. If no option value
is to be supplied or returned,
optval may be NULL.
Optname and any specified options are passed uninterpreted to the
appropriate protocol module for interpretation. The include file
<sys/socket.h> contains definitions for socket level options,
described below. Options at other protocol levels vary in format and name;
consult the appropriate entries in section 4 of the manual.
Most socket-level options utilize an
int parameter for
optval. For
setsockopt, the parameter should be non-zero to enable a boolean
option, or zero if the option is to be disabled.
For a description of the available socket options see
socket(7) and the
appropriate protocol man pages.
On success, zero is returned. On error, -1 is returned, and
errno is set
appropriately.
- EBADF
- The argument s is not a valid descriptor.
- EFAULT
- The address pointed to by optval is not in a valid
part of the process address space. For getsockopt, this error may
also be returned if optlen is not in a valid part of the process
address space.
- EINVAL
- optlen invalid in setsockopt
- ENOPROTOOPT
- The option is unknown at the level indicated.
- ENOTSOCK
- The argument s is a file, not a socket.
SVr4, 4.4BSD (these system calls first appeared in 4.2BSD). SVr4 documents
additional ENOMEM and ENOSR error codes, but does not document the
SO_SNDLOWAT,
SO_RCVLOWAT,
SO_SNDTIMEO,
SO_RCVTIMEO
options
The fifth argument of
getsockopt and
setsockopt is in reality an
int [*] (and this is what BSD 4.* and libc4 and libc5 have). Some POSIX
confusion resulted in the present socklen_t, also used by glibc. See also
accept(2).
Several of the socket options should be handled at lower levels of the system.
ioctl(2),
socket(2),
getprotoent(3),
protocols(5),
socket(7),
tcp(7),
unix(7)
