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System Calls close(2)
NAME
close - close a file descriptor
SYNOPSIS
#include <unistd.h>
int close(int fildes);
DESCRIPTION
The close() function deallocates the file descriptor indi-
cated by fildes. To deallocate means to make the file
descriptor available for return by subsequent calls to
open(2) or other functions that allocate file descriptors.
All outstanding record locks owned by the process on the
file associated with the file descriptor will be removed
(that is, unlocked).
If close() is interrupted by a signal that is to be caught,
it will return -1 with errno set to EINTR and the state of
fildes is unspecified. If an I/O error occurred while read-
ing from or writing to the file system during close(), it
returns -1, sets errno to EIO, and the state of fildes is
unspecified.
When all file descriptors associated with a pipe or FIFO
special file are closed, any data remaining in the pipe or
FIFO will be discarded.
When all file descriptors associated with an open file
description have been closed the open file description will
be freed.
If the link count of the file is 0, when all file descrip-
tors associated with the file are closed, the space occupied
by the file will be freed and the file will no longer be
accessible.
If a STREAMS-based (see intro(2)) fildes is closed and the
calling process was previously registered to receive a SIG-
POLL signal (see signal(3C)) for events associated with that
STREAM (see I_SETSIG in streamio(7I)), the calling process
will be unregistered for events associated with the STREAM.
The last close() for a STREAM causes the STREAM associated
with fildes to be dismantled. If O_NONBLOCK and O_NDELAY are
not set and there have been no signals posted for the
STREAM, and if there is data on the module's write queue,
close() waits up to 15 seconds (for each module and driver)
for any output to drain before dismantling the STREAM. The
time delay can be changed via an I_SETCLTIME ioctl(2)
request (see streamio(7I)). If the O_NONBLOCK or O_NDELAY
flag is set, or if there are any pending signals, close()
does not wait for output to drain, and dismantles the STREAM
SunOS 5.10 Last change: 18 Oct 2005 1
System Calls close(2)
immediately.
If fildes is associated with one end of a pipe, the last
close() causes a hangup to occur on the other end of the
pipe. In addition, if the other end of the pipe has been
named by fattach(3C), then the last close() forces the named
end to be detached by fdetach(3C). If the named end has no
open file descriptors associated with it and gets detached,
the STREAM associated with that end is also dismantled.
If fildes refers to the master side of a pseudo-terminal, a
SIGHUP signal is sent to the session leader, if any, for
which the slave side of the pseudo-terminal is the control-
ling terminal. It is unspecified whether closing the master
side of the pseudo-terminal flushes all queued input and
output.
If fildes refers to the slave side of a STREAMS-based
pseudo-terminal, a zero-length message may be sent to the
master.
When there is an outstanding cancelable asynchronous I/O
operation against fildes when close() is called, that I/O
operation is canceled. An I/O operation that is not canceled
completes as if the close() operation had not yet occurred.
All operations that are not canceled will complete as if the
close() blocked until the operations completed.
If a shared memory object or a memory mapped file remains
referenced at the last close (that is, a process has it
mapped), then the entire contents of the memory object will
persist until the memory object becomes unreferenced. If
this is the last close of a shared memory object or a memory
mapped file and the close results in the memory object
becoming unreferenced, and the memory object has been
unlinked, then the memory object will be removed.
If fildes refers to a socket, close() causes the socket to
be destroyed. If the socket is connection-mode, and the
SO_LINGER option is set for the socket with non-zero linger
time, and the socket has untransmitted data, then close()
will block for up to the current linger interval until all
data is transmitted.
RETURN VALUES
Upon successful completion, 0 is returned. Otherwise, -1 is
returned and errno is set to indicate the error.
ERRORS
The close() function will fail if:
SunOS 5.10 Last change: 18 Oct 2005 2
System Calls close(2)
EBADF The fildes argument is not a valid file
descriptor.
EINTR The close() function was interrupted by a
signal.
ENOLINK The fildes argument is on a remote machine
and the link to that machine is no longer
active.
ENOSPC There was no free space remaining on the
device containing the file.
The close() function may fail if:
EIO An I/O error occurred while reading from or
writing to the file system.
EXAMPLES
Example 1: Reassign a file descriptor.
The following example closes the file descriptor associated
with standard output for the current process, re-assigns
standard output to a new file descriptor, and closes the
original file descriptor to clean up. This example assumes
that the file descriptor 0, which is the descriptor for
standard input, is not closed.
#include <unistd.h>
...
int pfd;
...
close(1);
dup(pfd);
close(pfd);
...
Incidentally, this is exactly what could be achieved using:
dup2(pfd, 1);
close(pfd);
SunOS 5.10 Last change: 18 Oct 2005 3
System Calls close(2)
Example 2: Close a file descriptor.
In the following example, close() is used to close a file
descriptor after an unsuccessful attempt is made to associ-
ate that file descriptor with a stream.
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#define LOCKFILE "/etc/ptmp"
...
int pfd;
FILE *fpfd;
...
if ((fpfd = fdopen (pfd, "w")) == NULL) {
close(pfd);
unlink(LOCKFILE);
exit(1);
}
...
USAGE
An application that used the stdio function fopen(3C) to
open a file should use the corresponding fclose(3C) function
rather than close().
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Interface Stability | Standard |
|_____________________________|_____________________________|
| MT-Level | Async-Signal-Safe |
|_____________________________|_____________________________|
SEE ALSO
intro(2), creat(2), dup(2), exec(2), fcntl(2), ioctl(2),
open(2) pipe(2), fattach(3C), fclose(3C), fdetach(3C),
fopen(3C), signal(3C), signal.h(3HEAD), attributes(5), stan-
dards(5), streamio(7I)
SunOS 5.10 Last change: 18 Oct 2005 4
Man(1) output converted with
man2html and wrapped by fishsponge
This page was generated on Wed Sep 12 21:37:21 GMT 2007
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