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C Interface
int shutdown (s, how)
int s, how;
Description
The shutdown system call is used to shut down a socket. The
s parameter is the socket descriptor of the socket to be shut
down. In the case of a full-duplex connection, shutdown can be used
to either partially or fully shut down the socket, depending on the value of
how.
If how=0, the socket can still send data, but it cannot
receive data. Remaining data can be sent and new data can be sent; however,
all further recv() calls return an end-of-file condition.
If how=1, further sends by the user will return an EPIPE error.
A SIGPIPE signal will be sent to the user unless the user has used
ioctl() to ignore the signal. Note that data already queued by a
previous send call will still be sent.
If how=2, a socket cannot send remaining or new data or
receive data. This is the same as doing a shutdown of 0 and a shutdown of 1
simultaneously.
Once the socket has been shut down for receives, all further recv
calls return an end-of-file condition.
A shutdown on a connection-less socket, such as SOCK_DGRAM,
only marks the socket unable to do further sends or receives, depending on
how. Once this type of socket has been disabled for both
sending and receiving data, it becomes fully shut down.
For SOCK_STREAM sockets, if how is 1 or 2, the
connection begins a graceful disconnect. The disconnection is complete when
both sides of the connection have done a shutdown with
how equal to 1 or 2. Once the connection has been completely
terminated, the socket becomes fully shut down.
Note the difference between the close and shutdown calls.
Close makes the socket descriptor invalid while shutdown is
used to partially or fully shutdown the I/O on the socket. The user can call
close after a shutdown to make the socket descriptor unusable. The
SO_LINGER option does not have any meaning for the shutdown
call, but does for the close call. (Refer to
setsockopt.)
Return Value
If the call is successful, a 0 is returned. If it fails, a -1 is returned, and
an error code is stored in errno.
Errors
The following errors are returned by shutdown:
| Error Code |
Description |
| [EBADF] |
The arguments is not a valid descriptor. |
| [ENOTSOCK] |
The argument s is a file, not a socket. |
| [EINVAL] |
The specified socket is not connected. |
Author
UCB (University of California at Berkeley)
See Also
close,
connect,
ioctl,
socket
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