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.TH io_fd_flags 3
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.SH NAME
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io_fd_flags \- 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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#ifdef HAVE_IO_FD_FLAGS
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int \fBio_fd_flags\fP(int64 fd);
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.SH DESCRIPTION
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io_fd_flags behaves just like io_fd, but certain flags can be
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bitwise-ORed to it to alter its behavior:
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.RS 0
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.IP IO_FD_CANWRITE
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tell io_fd that the descriptor is writable. This is useful so
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io_wantwrite can queue the descriptor immediately and there is no need
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to query the operating system event reporting mechanism.
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.IP IO_FD_BLOCK
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tell io_fd that the descriptor is blocking.
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.IP IO_FD_NONBLOCK
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tell io_fd that the descriptor is non-blocking.
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.RE
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Normally, io_fd calls fcntl to ask the operating system whether the
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descriptor is blocking or not. The frameworks needs to know because it
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alters how io_tryread and io_trywrite handle the socket. Never pass
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both IO_FD_BLOCK and IO_FD_NONBLOCK at the same time.
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Newly connected stream sockets are always writable if the connection is
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established, so it is usually safe to pass IO_FD_CANWRITE. The main
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exception case where IO_FD_CANWRITE should not be passed is on a
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non-blocking socket where a connect() is pending. Then you need to poll
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for writability to get notified when the connection is established.
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.SH "RETURN VALUE"
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io_fd_flags returns 1 on success, 0 on error.
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.SH "SEE ALSO"
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io_fd(3), io_fd_canwrite(3)
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