V3/usr/man/man2/write.2

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NAME		write  --  write on file
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SYNOPSIS	(file descriptor in r0)
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sys write; buffer; nbytes  / write = 4.
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(number written in r0)
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DESCRIPTION	A file descriptor is a word returned from a
successful open____ or creat_____ call.
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buffer______ is the address of nbytes______ contiguous
bytes which are written on the output file.
The number of characters actually written is returned in r0.
It should be regarded as an error
if this is not the same as requested.
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Writes which are multiples
of 512 characters long and begin on a 512-byte boundary
are more efficient than any others.
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SEE ALSO	creat(II), open(II)
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DIAGNOSTICS	The error bit
(c-bit) is set on an error: bad descriptor, buffer address, or
count; physical I/O errors.
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BUGS		--