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.TH io_canwrite 3
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.SH NAME
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io_canwrite \- return a file descriptor that can be written to
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.SH SYNTAX
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.B #include <libowfat/io.h>
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int64 \fBio_canwrite\fP();
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.SH DESCRIPTION
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io_canwrite returns the next file descriptor that can be written to.
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You have to have used io_wantwrite() on the file descriptor earlier, and
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you have to have called io_wait() or io_waituntil().
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These functions then keep an internal data structure on which
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descriptors were reported writable by the operating system.
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Please note that there is no guarantee that you can still write data
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without blocking to that descriptor, just that you could when io_wait()
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or io_waituntil() were called. Another process could have written
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something before you. Look at the result from io_trywrite().
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If there are no more descriptors that you can write to without blocking,
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io_canwrite will return -1. In this case you should call io_wait() or
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io_waituntil() again.
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You should only use io_trywrite(3), io_sendfile(3) or iob_send(3) to
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write to the file, not plain write(2). If you use write(2) and get
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EAGAIN, call io_eagain(3).
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.SH "SEE ALSO"
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io_wait(3), io_canwrite(3)
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