close(2)close(2)NAMEclose - Close the file associated with a file descriptor
SYNOPSIS
#include <unistd.h>
int close(
int filedes );
STANDARDS
Interfaces documented on this reference page conform to industry stan‐
dards as follows:
close(): XSH4.0, XSH4.2, XSH5.0, XNS4.0, XNS5.0
Refer to the standards(5) reference page for more information about
industry standards and associated tags.
PARAMETERS
Specifies a valid open file descriptor.
DESCRIPTION
The close() function closes the file associated with the filedes param‐
eter.
All regions of a file specified by the filedes parameter that this
process has previously locked with the lockf() function are unlocked.
This occurs even if the process still has the file open by another file
descriptor.
When all file descriptors associated with a pipe or FIFO special file
have been closed, any data remaining in the pipe or FIFO is discarded.
When all file descriptors associated with an open file descriptor are
closed, the open file descriptor is freed. If the link count of the
file is 0 (zero) when all file descriptors associated with the file
have been closed, the space occupied by the file is freed and the file
is no longer accessible.
When the close() function needs to block, only the calling thread is
suspended rather than all threads in the calling process.
The last close() for a stream causes the stream associated with fildes
to be dismantled. Dismantling includes popping any modules on the
stream and closing the driver. If O_NDELAY and O_NONBLOCK are clear and
there are no signals posted for the stream, close() waits up to 15 sec‐
onds for each module to drain and up to 15 seconds for each driver to
drain. If the O_NDELAY or the O_NONBLOCK option is set or if there are
any pending signals, close() does not wait for output to drain, and
dismantles the stream immediately. If a STREAMS file is closed, and the
calling process had previously registered to receive a SIGPOLL signal
[see signal()] for events associated with that file [see I_SETSIG in
streamio(7)], the calling process is unregistered for events associated
with the file.
For sockets (fildes refers to a socket), a call to close causes the
socket to be destroyed. For connection-oriented sockets that have the
SOCK_LINGER option set and have untransmitted data, the close function
blocks for the period of time specified by the linger interval until
all data is transmitted.
RETURN VALUES
Upon successful completion, a value of 0 (zero) is returned. Otherwise,
a value of -1 is returned and errno is set to indicate the error.
ERRORS
If the close() function fails, errno may be set to one of the following
values: The filedes parameter is not a valid open file descriptor. The
close() function was interrupted by a signal which was caught. A read
or write physical I/O error. [Tru64 UNIX] fildes is on a remote
machine and the link to that machine is no longer active.
[Tru64 UNIX] A close() function on an NFS file system waits for all
outstanding I/O to complete. If any operation completes with an error,
the error will be returned by close(). The possible errors depend on
the NFS server implementation, but the most likely errors are: The
write has failed because the user's disk block quota is exhausted.
Attempted to write a file that exceeds the maximum file size. A read
or write physical I/O error. Attempted to write on a full file system.
SEE ALSO
Functions: exec(2), fcntl(2), lockf(3), open(2), pipe(2), socket(2),
streamio(7).
Standards: standards(5).
Network Programmer's Guide
close(2)
