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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.  Note that the return value should only be used for diagnostics.
       In particular close() should not be retried after an EINTR  since  this
       may cause a reused descriptor from another thread to be closed.

       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 filesystem 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 3.65 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/.



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