GETC(III)                    4/30/72                    GETC(III)

     getc, getw, fopen  -  buffered input

     mov  $filename,r0
     jsr  r5,fopen; iobuf

     fopen(filename, iobuf)
     char *filename;
     struct buf *iobuf;

     jsr  r5,getc; iobuf
     (character in r0)

     struct buf *iobuf;

     jsr  r5,getw; iobuf
     (word in r0)

     struct buf *iobuf;

     These  routines provide a buffered input facility.  Iobuf is
     the address of a 518(10) byte buffer area whose contents are
     maintained by these routines.  Its structure is

          struct buf {
               int fildes;    /* File descriptor */
               int nleft;     /* Chars left in buffer */
               char *nextp;   /* Ptr to next character */
               char buff[512];     /* The buffer */

     Fopen  may be called initially to open the file.  On return,
     the error bit (c-bit) is set if the open failed.   If  fopen
     is never called, get will read from the standard input file.
     From C, the value is negative if the open failed.

     Getc returns the next byte from the file in r0.   The  error
     bit  is  set  on  end  of file or a read error.  From C, the
     character is returned as an integer, without sign extension;
     it is -1 on end-of-file or error.

     Getw returns the next word in r0.  Getc and getw may be used
     alternately; there are no odd/even problems.  Getw is may be
     called  from  C; -1 is returned on end-of-file or error, but
     of course is also a legitimate value.

     Iobuf must be provided by the user; it must  be  on  a  word

     To  reuse the same buffer for another file, it is sufficient
     to close the original file and call fopen again.

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GETC(III)                    4/30/72                    GETC(III)

     open(II), read(II), getchar(III), putc(III)

     c-bit set on EOF or error; from C, negative return indicates
     error  or  EOF.  Moreover, errno is set by this routine just
     as it is for a system call (see introduction(II)).


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