V3/usr/man/man2/open.2

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NAME		open  --  open for reading or writing
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SYNOPSIS	sys open; name; mode  / open = 5.
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(descriptor in r0)
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DESCRIPTION	open____ opens the file name____ for reading
(if mode____ is 0) or writing (if mode____ is non-zero).
name____ is the address of a string of ASCII characters representing
a path name, terminated by a null character.
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The file descriptor should be saved for subsequent calls
to read (or write) and close.
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In both the read and write case the file pointer
is set to the beginning of the file.
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SEE ALSO	creat(II), read(II), write(II), close(II)
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DIAGNOSTICS	The error bit
(c-bit) is set if the file does not exist,
if one of the necessary directories
does not exist or is unreadable, if the file is not
readable (resp. writable), or if 10 files are open.
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BUGS		--