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@(#)close.2 8.2 (Berkeley) 4/19/94
$FreeBSD$
.Dd September 11, 2013 .Dt CLOSE 2 .Os .Sh NAME .Nm close .Nd delete a descriptor .Sh LIBRARY .Lb libc .Sh SYNOPSIS n unistd.h .Ft int .Fn close "int fd" .Sh DESCRIPTION The .Fn close system call deletes a descriptor from the per-process object reference table. If this is the last reference to the underlying object, the object will be deactivated. For example, on the last close of a file the current .Em seek pointer associated with the file is lost; on the last close of a .Xr socket 2 associated naming information and queued data are discarded; on the last close of a file holding an advisory lock the lock is released (see further .Xr flock 2 ) . However, the semantics of System V and .St -p1003.1-88 dictate that all .Xr fcntl 2 advisory record locks associated with a file for a given process are removed when .Em any file descriptor for that file is closed by that process.
p When a process exits, all associated file descriptors are freed, but since there is a limit on active descriptors per processes, the .Fn close system call is useful when a large quantity of file descriptors are being handled.
p When a process forks (see .Xr fork 2 ) , all descriptors for the new child process reference the same objects as they did in the parent before the fork. If a new process is then to be run using .Xr execve 2 , the process would normally inherit these descriptors. Most of the descriptors can be rearranged with .Xr dup2 2 or deleted with .Fn close before the .Xr execve 2 is attempted, but if some of these descriptors will still be needed if the execve fails, it is necessary to arrange for them to be closed if the execve succeeds. For this reason, the call .Dq Li fcntl(d, F_SETFD, FD_CLOEXEC) is provided, which arranges that a descriptor will be closed after a successful execve; the call .Dq Li fcntl(d, F_SETFD, 0) restores the default, which is to not close the descriptor. .Sh RETURN VALUES .Rv -std close .Sh ERRORS The .Fn close system call will fail if: l -tag -width Er t Bq Er EBADF The .Fa fd argument is not an active descriptor. t Bq Er EINTR An interrupt was received. t Bq Er ENOSPC The underlying object did not fit, cached data was lost. t Bq Er ECONNRESET The underlying object was a stream socket that was shut down by the peer before all pending data was delivered. .El
p In case of any error except .Er EBADF , the supplied file descriptor is deallocated and therefore is no longer valid. .Sh SEE ALSO .Xr accept 2 , .Xr closefrom 2 , .Xr execve 2 , .Xr fcntl 2 , .Xr flock 2 , .Xr open 2 , .Xr pipe 2 , .Xr socket 2 , .Xr socketpair 2 .Sh STANDARDS The .Fn close system call is expected to conform to .St -p1003.1-90 . .Sh HISTORY The .Fn close function appeared in .At v7 .