| CLOSE(2) | System Calls Manual | CLOSE(2) |
close — delete a
descriptor
#include
<unistd.h>
int
close(int
d);
The
close()
call deletes a descriptor d 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
seek
pointer associated with the file is lost; on the last close of a
socket(2), associated naming information and queued data
are discarded; and on the last close of a file holding an advisory lock, the
lock is released (see flock(2)). However, the semantics of
System V and IEEE Std 1003.1-1988
(“POSIX.1”) dictate that all fcntl(2)
advisory record locks associated with a file for a given process are removed
when any
file descriptor for that file is closed by that process.
When a process forks (see 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 image is to then be run
using execve(2), the process would normally inherit these
descriptors. Most of the descriptors can be rearranged with
dup2(2) or deleted with
close()
before the execve(2) is attempted, but since some of these
descriptors may still be needed should the execve(2) fail,
it is necessary to arrange for them to be closed when the
execve(2) succeeds. For this reason, the call
fcntl(d,
F_SETFD, FD_CLOEXEC) is
provided, which arranges that a descriptor will be closed after a successful
execve(2); the call
fcntl(d,
F_SETFD, 0) restores the
default, which is to not close the descriptor.
Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the error.
close() will fail if:
accept(2), closefrom(2), dup2(2), execve(2), fcntl(2), flock(2), open(2), pipe(2), socket(2), socketpair(2)
close() conforms to IEEE
Std 1003.1-2008 (“POSIX.1”).
The close() system call first appeared in
Version 1 AT&T UNIX.
| April 15, 2022 | Debian |