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shutdown — disable sends and/or receives on a socket
Standard C Library (libc, -lc)
#include <sys/types.h> #include <sys/socket.h> int shutdown(int s, int how);
The shutdown() system call disables sends or receives on a socket. The how argument specifies the type of shutdown. Possible values are: SHUT_RD Further receives will be disallowed. SHUT_WR Further sends will be disallowed. This may cause actions specific to the protocol family of the socket s to happen; see IMPLEMENTATION NOTES. SHUT_RDWR Further sends and receives will be disallowed. Implies SHUT_WR. If the file descriptor s is associated with a SOCK_STREAM socket, all or part of the full- duplex connection will be shut down.
The following protocol specific actions apply to the use of SHUT_WR (and potentially also SHUT_RDWR), based on the properties of the socket associated with the file descriptor s. Domain Type Protocol Return value and action PF_INET SOCK_DGRAM IPPROTO_SCTP Return -1. The global variable errno will be set to EOPNOTSUPP. PF_INET SOCK_DGRAM IPPROTO_UDP Return 0. ICMP messages will not be generated. PF_INET SOCK_STREAM IPPROTO_SCTP Return 0. Send queued data and tear down association. PF_INET SOCK_STREAM IPPROTO_TCP Return 0. Send queued data, wait for ACK, then send FIN. PF_INET6 SOCK_DGRAM IPPROTO_SCTP Return -1. The global variable errno will be set to EOPNOTSUPP. PF_INET6 SOCK_DGRAM IPPROTO_UDP Return 0. ICMP messages will not be generated. PF_INET6 SOCK_STREAM IPPROTO_SCTP Return 0. Send queued data and tear down association. PF_INET6 SOCK_STREAM IPPROTO_TCP Return 0. Send queued data, wait for ACK, then send FIN.
The shutdown() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.
The shutdown() system call fails if: [EBADF] The s argument is not a valid file descriptor. [EINVAL] The how argument is invalid. [EOPNOTSUPP] The socket associated with the file descriptor s does not support this operation. [ENOTCONN] The s argument specifies a SOCK_STREAM socket which is not connected. [ENOTSOCK] The s argument does not refer to a socket.
The shutdown() system call is expected to comply with IEEE Std 1003.1g-2000 (“POSIX.1”), when finalized.
The shutdown() system call appeared in 4.2BSD. The SHUT_RD, SHUT_WR, and SHUT_RDWR constants appeared in IEEE Std 1003.1g-2000 (“POSIX.1”).
This manual page was updated by Bruce M. Simpson <bms@FreeBSD.org> to reflect how shutdown() behaves with PF_INET and PF_INET6 sockets.
The ICMP “port unreachable” message should be generated in response to datagrams received on a local port to which s is bound after shutdown() is called.