11/3/71 SYS READ (II)
NAME read -- read from file
SYNOPSIS (file descriptor in r0)
sys read; buffer; nchars / read = 3.
(nread in r0)
DESCRIPTION A file descriptor is a word returned from a suc-
cessful open call.
Buffer is the location of nchars contiguous bytes
into which the input will be placed. It is not
guaranteed that all nchars bytes will be read,
however; for example if the file refers to a
typewriter at most one line will be returned. In
any event the number of characters read is re-
turned in r0.
If r0 returns with value 0, then end-of-file has
been reached.
FILES --
SEE ALSO open
DIAGNOSTICS As mentioned, r0 is 0 on return when the end of
the file has been reached. If the read was
otherwise unsuccessful the error bit (c-bit) is
set. Many conditions, all rare, can generate an
error: physical I/O errors, bad buffer address,
preposterous nchars, file descriptor not that of
an input file.
BUGS --
OWNER ken, dmr