Unix |
Unix v6 |
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read(2) |
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read read from file (read = 3.)
(file descriptor in r0)
sys read; buffer; nbytes
read(fildes, buffer, nbytes)
char *buffer; A file descriptor is a word returned from
a successful or call. is the location of contiguous bytes
into which the input will be placed. It is not guaranteed
that all bytes will be read; 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 returned (in r0). If
the returned value is 0, then end-of-file has been reached.
open (II), creat (II), dup (II), pipe (II) As mentioned, 0
is returned when the end of the file has been reached. If
the read was otherwise unsuccessful the error bit (c-bit) is
set. Many conditions can generate an error: physical I/O
errors, bad buffer address, preposterous file descriptor not
that of an input file. From C, a 1 return indicates the
error.
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read(2) |
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