NAME

read − read from file

SYNOPSIS

(read = 3.) 
(file descriptor in r0)
sys read; buffer; nbytes
read(fildes, buffer, nbytes)
char *buffer;

DESCRIPTION

A file descriptor is a word returned from a successful "open, creat, dup," or pipe call.  Buffer is the location of nbytes contiguous bytes into which the input will be placed.  It is not guaranteed that all nbytes 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.

SEE ALSO

open (II), creat (II), dup (II), pipe (II)

DIAGNOSTICS

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 nbytes, file descriptor not that of an input file.  From C, a −1 return indicates the error.