(flex.info)Why do flex scanners call fileno if it is not ANSI compatible?

---

Next: Does flex support recursive pattern definitions? Prev: How do I expand backslash-escape sequences in C-style quoted strings? Up: FAQ

---

Enter node , (file) or (file)node

Why do flex scanners call fileno if it is not ANSI compatible?
==============================================================

Flex scanners call 'fileno()' in order to get the file descriptor
corresponding to 'yyin'.  The file descriptor may be passed to
'isatty()' or 'read()', depending upon which '%options' you specified.
If your system does not have 'fileno()' support, to get rid of the
'read()' call, do not specify '%option read'.  To get rid of the
'isatty()' call, you must specify one of '%option always-interactive' or
'%option never-interactive'.