01-10-2009
I fail to see what you gain by doing this as a general idea.
In theory close the descriptors, then open them again directed somewhere else.
As a special case:
When you write a daemon all three of these descriptors are closed and then often reopened and directed to /dev/null. This means because the process runs "in the dark" it cannot directly write or read any of the standard descriptors. This prevents signals like SIGTTOU being sent to the process if it inadvertantly tries to write to stdout while running in detached mode.
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LEARN ABOUT DEBIAN
io_canread
io_canread(3) Library Functions Manual io_canread(3)
NAME
io_canread - return a file descriptor that can be read from
SYNTAX
#include <io.h>
int64 io_canread();
DESCRIPTION
io_canread returns the next file descriptor that can be read from. You have to have used io_wantread() on the file descriptor earlier, and
you have to have called io_wait() or io_waituntil().
These functions then keep an internal data structure on which descriptors were reported readable by the operating system.
Please note that there is no guarantee that there still is data that can be read from the descriptor, just that there was data when
io_wait() or io_waituntil() were called. Another process could have read the data before you. Look at the result from io_tryread().
If there are no more descriptors that you can write to without blocking, io_canwrite will return -1. In this case you should call
io_wait() or io_waituntil() again.
You should use io_tryread(3) to read from the descriptor, not plain read(2). If you use read(2) and you get EAGAIN, call io_eagain(3).
SEE ALSO
io_wait(3), io_canwrite(3), io_eagain(3)
io_canread(3)