Shut down part of a full-duplex connection
#include <sys/socket.h>
int shutdown(int sockfd, int how);
The shutdown() call causes all or part of a full-duplex connection on the socket associated with sockfd to be shut down. If how is SHUT_RD, further receptions will be disallowed. If how is SHUT_WR, further transmissions will be disallowed. If how is SHUT_RDWR, further receptions and transmissions will be disallowed.
On success, zero is returned. On error, -1 is returned, and errno is set appropriately.
EBADF
sockfd is not a valid descriptor.
EINVAL
An invalid value was specified in how (but see BUGS).
ENOTCONN
The specified socket is not connected.
ENOTSOCK
sockfd is a file, not a socket.
POSIX.1-2001, 4.4BSD (the shutdown() function call first appeared in 4.2BSD).
The constants SHUT_RD, SHUT_WR, SHUT_RDWR have the value 0, 1, 2, respectively, and are defined in <sys/socket.h> since glibc-2.1.91.
As currently implemented, checks for the validity of how are done in domain-specific code, and not all domains perform these checks. Most notably, UNIX domain sockets simply ignore invalid values; this may change in the future.
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