NAME
close —
delete a descriptor
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <unistd.h>
int
close(
int
d);
DESCRIPTION
The
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
seek pointer associated with the
file is lost; on the last close of a
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
flock(2)).
When a process exits, all associated descriptors are freed, but since there is a
limit on active descriptors per processes, the
close()
system call is useful when a large quantity of file descriptors are being
handled.
When a process calls
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
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()
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 only if the
execve() succeeds. For this reason, the
system call
is provided, which arranges that a descriptor
“
d” will be closed after a successful
execve(); the system call
restores the default, which is to not close descriptor
“
d”.
RETURN VALUES
Upon successful completion, a value of 0 is returned. Otherwise, a value of -1
is returned and
errno is set to indicate the error.
ERRORS
close() will fail if:
-
-
- [
EBADF
]
- d is not an active descriptor.
-
-
- [
EINTR
]
- An interrupt was received.
SEE ALSO
accept(2),
execve(2),
fcntl(2),
flock(2),
open(2),
pipe(2),
socket(2),
socketpair(2)
STANDARDS
The
close() function conforms to
IEEE Std
1003.1-1990 (“POSIX.1”).