shutdown - 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.
sockfd is not a valid file descriptor.
An invalid value was specified in how (but see BUGS).
The specified socket is not connected.
The file descriptor sockfd does not refer to a socket.
POSIX.1-2001, POSIX.1-2008, 4.4BSD (shutdown() 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.
Checks for the validity of how are done in domain-specific code, and before Linux 3.7 not all domains performed these checks. Most notably, UNIX domain sockets simply ignored invalid values. This problem was fixed for UNIX domain sockets in Linux 3.7.
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