v7 man page for open

OPEN(2) 							System Calls Manual							   OPEN(2)

NAME
       open - open for reading or writing

SYNOPSIS
       open(name, mode)
       char *name;

DESCRIPTION
       Open  opens  the  file name for reading (if mode is 0), writing (if mode is 1) or for both reading and writing (if mode is 2).  Name is the
       address of a string of ASCII characters representing a path name, terminated by a null character.

       The file is positioned at the beginning (byte 0).  The returned file descriptor must be used for subsequent calls  for  other  input-output
       functions on the file.

SEE ALSO
       creat(2), read(2), write(2), dup(2), close(2)

DIAGNOSTICS
       The  value  -1  is returned 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 too many files are open.

ASSEMBLER
       (open = 5.)
       sys open; name; mode
       (file descriptor in r0)

																	   OPEN(2)