close(2) [ultrix man page]

close(2) System Calls Manual close(2)

Name
close - delete a descriptor

Syntax
close(fd)
int fd;

Description
The call deletes a descriptor from the per-process object reference table. If the descriptor is the last reference to the underlying
object, then the object is deactivated. For example, on the last close of a file, the current pointer associated with the file is lost.
On the last close of a socket, discards associated naming information and queued data. On the last close of a file holding an advisory
lock, the lock is released. For further information, see

A process's descriptors are automatically closed when a process exits, but because each process can have a limited number of active
descriptors, is necessary for programs that deal with many descriptors.

When a process forks, all descriptors for the new child process reference the same objects as they did in the parent process before the
fork. For further information, see If a new process is then to be run using the process would normally inherit these descriptors. Most of
the descriptors can be rearranged with the system call or deleted with before is called. However, if any descriptors are needed if the
fails, they must be closed if the execve succeeds. For this reason, the call, fcntl(d, F_SETFD, 1), is provided. This call arranges that a
descriptor is closed after a successful call. The call, fcntl(d, F_SETFD, 0), restores the default, which is to not close the descriptor.

When is used on a descriptor that refers to a remote file over NFS, and that file has been modified by using then any cached data is
flushed before returns. If an asynchronous write error has occurred previously with this remote file, or occurred as part of the flush
operation described above, then returns -1 and errno will be set to the error code. The return code from should be inspected by any program
that can over NFS.

Return Values
Upon successful completion, a value of 0 is returned. Otherwise, a value of -1 is returned, and the global integer variable, errno, is set
to indicate the error.

Diagnostics
The system call fails under the following conditions:

[EBADF] D is not an active descriptor.

[EINTR] The function was interrupted by a signal.

If an error occurs on an asynchronous write over NFS, the error cannot always be returned from a system call. The error code is returned
on or The following are NFS-only error messages:

[EACCESS] The requested address is protected, and the current user has inadequate permission to access it.

[ENOSPC] There is no free space remaining on the file system containing the file.

[EDQUOT] The user's quota of disk blocks on the file system containing the file has been exhausted.

[EIO] An I/O error occurred while reading from or writing to the file system.

[EROFS] The file is on a read-only file system.

[ESTALE] The fd argument is invalid because the file referred to by that file handle no longer exists or has been revoked.

[ETIMEDOUT] A write operation failed because the server did not properly respond after a period of time that is dependent on the
options.

See Also
accept(2), execve(2), fcntl(2), flock(2), fsync(2), open(2), pipe(2), socket(2), socketpair(2), write(2)

close(2)

Check Out this Related Man Page

CLOSE(2)						     Linux Programmer's Manual							  CLOSE(2)

NAME

       close - close a file descriptor

SYNOPSIS

       #include <unistd.h>

       int close(int fd);

DESCRIPTION

       close()	closes	a file descriptor, so that it no longer refers to any file and may be reused.  Any record locks (see fcntl(2)) held on the
       file it was associated with, and owned by the process, are removed (regardless of the file descriptor that was used to obtain the lock).

       If fd is the last file descriptor referring to the underlying open file description (see open(2)), the resources associated with  the  open
       file description are freed; if the descriptor was the last reference to a file which has been removed using unlink(2) the file is deleted.

RETURN VALUE

       close() returns zero on success.  On error, -1 is returned, and errno is set appropriately.

ERRORS

       EBADF  fd isn't a valid open file descriptor.

       EINTR  The close() call was interrupted by a signal; see signal(7).

       EIO    An I/O error occurred.

CONFORMING TO

       SVr4, 4.3BSD, POSIX.1-2001.

NOTES

       Not  checking  the  return  value of close() is a common but nevertheless serious programming error.  It is quite possible that errors on a
       previous write(2) operation are first reported at the final close().  Not checking the return value when  closing  the  file  may  lead	to
       silent loss of data.  This can especially be observed with NFS and with disk quota.

       A successful close does not guarantee that the data has been successfully saved to disk, as the kernel defers writes.  It is not common for
       a file system to flush the buffers when the stream is closed.  If you need to be sure that the data is physically stored use fsync(2).  (It
       will depend on the disk hardware at this point.)

       It  is  probably  unwise  to close file descriptors while they may be in use by system calls in other threads in the same process.  Since a
       file descriptor may be reused, there are some obscure race conditions that may cause unintended side effects.

SEE ALSO

       fcntl(2), fsync(2), open(2), shutdown(2), unlink(2), fclose(3)

COLOPHON

       This page is part of release 3.27 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    2007-12-28								  CLOSE(2)

Linux and UNIX Man Pages

close(2) [ultrix man page]

Check Out this Related Man Page