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.TH io_fd 3
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.SH NAME
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io_fd \- prepare descriptor for io_wait
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.SH SYNTAX
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.B #include <libowfat/io.h>
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int \fBio_fd\fP(int64 fd);
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.SH DESCRIPTION
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If you want to use io_canread() and io_canwrite() on a descriptor, you
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have to use io_wait() on it first, and io_wait() has to know which
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descriptors you are interested in. io_fd() informs io_wait() that you
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are interested in this fd.
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If you know that the descriptor is writable, call io_fd_canwrite()
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instead. Most fresh descriptors are writable, e.g. if it came from
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pipe(2) or socketpair(2) or accept(2). This will save one syscall.
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io_pipe and io_socketpair already call io_fd_canwrite() for you.
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Waiting on descriptors only works for sockets, fifos and pipes. It may
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also work on devices and TTYs, but that is platform dependent -- you
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should not rely on that. It does not work on files.
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.SH "RETURN VALUE"
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io_fd returns 1 on success, 0 on error.
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.SH "SEE ALSO"
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io_fd_canwrite(3), io_wait(3), io_wantread(3), io_canread(3), io_eagain(3), io_nonblock(3)
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