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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 appro-
priately.
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 pro-
gramming 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 clos-
ing 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 physi-
cally 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 re-
used, 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 3.22 of the Linux man-pages project. A description of
the project, and information about reporting bugs, can be found at http://www.ker-
nel.org/doc/man-pages/.
Linux 2007-12-28 CLOSE(2)
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