Intel XENIX 286 Programmers Guide (86) - Tenox.tc

lex: Lexical Analyzer Generator XENIX Programming
If any of these characters are to be used literally, they must be quoted individually with
a backslash (\) or as a group within quotation marks ("). Whatever is contained between
a pair of quotation marks is to be taken as text characters. Thus
xyz" + +
matches the string xyz++ when it appears. Note that a part of a string may be quoted.
It is harmless but unnecessary to quote an ordinary text character; the expression
"xyz + +
is the same as the one above. Thus by quoting every nonalphanumeric character being
used as a text character, you need not memorize the above list of current operator
characters.
An operator character may also be turned into a text character by preceding it with a
backslash (\) as in
xyz\ + \ +
which is another, less readable, equivalent of the above expressions. The quoting
mechanism can also be used to get a blank into an expression; normally, as explained
above, blanks or tabs end a rule. Any blank character not contained within brackets
must be quoted. Several normal C escapes with the backslash (\) are recognized:
\n newline
\t tab
\b backspace
\\ backslash
Since newline is illegal in an expression, \n must be used; it is not required to escape tab
and backspace. Every character but blank, tab, newline, backspace, and backslash is
always a text character.
Invoking lex
There are two steps in compiling a lex source program. First, the lex source must be
turned into a generated C program. Then this program must be compiled and loaded,
usually with a library of lex subroutines. The generated program is in a file named
lex.yy.c. The lex 1/0 library is defined in terms of the C standard library.
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