close(), exceptions and problems

[Marcin 'Qrczak' Kowalczyk]

Sat, 24 Mar 2001 12:23:03 +0000 (UTC), Erwin S. Andreasen <erwin at andreasen.com> pisze:

> But if you call close(fd) you aren't supposed to do something like:
> 
> int fd, rv;
> while (((rv = close(fd)) < 0 && errno == EINTR))
> 	;
> if (rv < 0)
> 	perror("close");

Linux documentation says otherwise.

File: libc.info,  Node: Opening and Closing Files,  Next: I/O Primitives,  Up: Low-Level I/O

[...]

 - Function: int close (int FILEDES)
     The function `close' closes the file descriptor FILEDES.  Closing
     a file has the following consequences:

        * The file descriptor is deallocated.

        * Any record locks owned by the process on the file are
          unlocked.

        * When all file descriptors associated with a pipe or FIFO have
          been closed, any unread data is discarded.

     This function is a cancellation point in multi-threaded programs.
     This is a problem if the thread allocates some resources (like
     memory, file descriptors, semaphores or whatever) at the time
     `close' is called.  If the thread gets cancelled these resources
     stay allocated until the program ends.  To avoid this, calls to
     `close' should be protected using cancellation handlers.

     The normal return value from `close' is 0; a value of -1 is
     returned in case of failure.  The following `errno' error
     conditions are defined for this function:

    `EBADF'
          The FILEDES argument is not a valid file descriptor.

    `EINTR'
          The `close' call was interrupted by a signal.  *Note
          Interrupted Primitives::.  Here is an example of how to
          handle `EINTR' properly:

               TEMP_FAILURE_RETRY (close (desc));

    `ENOSPC'
    `EIO'
    `EDQUOT'
          When the file is accessed by NFS, these errors from `write'
          can sometimes not be detected until `close'.  *Note I/O
          Primitives::, for details on their meaning.

-- 
 __("<  Marcin Kowalczyk * qrczak at knm.org.pl http://qrczak.ids.net.pl/
 \__/
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QRCZAK