LEX(1)			 HP-UX 5.0			LEX(1)

     NAME
	  lex - generate programs for lexical analysis of text

     SYNOPSIS
	  lex [ -rctvn ] [ file ] ...

     HP-UX COMPATIBILITY
	  Level:    HP-UX/STANDARD

	  Origin:   System III

     DESCRIPTION
	  Lex generates programs to be used in simple lexical analysis
	  of text.

	  The input  files  contain  strings  and  expressions	to  be
	  searched  for,  and  C  text to be executed when strings are
	  found.  Multiple files are treated as a single file.	If  no
	  files are specified, the standard input is used.

	  A file lex.yy.c is generated which,  when  loaded  with  the
	  library, copies the input to the output except when a string
	  specified in the  file  is  found;  then  the	 corresponding
	  program text is executed.  The actual string matched is left
	  in yytext, an external character array.  Matching is done in
	  order	 of  the strings in the file.  The strings may contain
	  square brackets to indicate character classes, as in [abx-z]
	  to indicate a, b, x, y, and z; and the operators *, +, and ?
	  mean respectively any non-negative number of,	 any  positive
	  number  of,  and  either  zero  or  one  occurrences of, the
	  previous character or character class.  The character	 .  is
	  the	class	of   all  ASCII	 characters  except  new-line.
	  Parentheses for grouping and vertical	 bar  for  alternation
	  are also supported.  The notation r{d,e} in a rule indicates
	  between d and e instances of regular expression r.   It  has
	  higher  precedence  than  |,	but  lower  than  *, ?, +, and
	  concatenation.  The character	 ^  at	the  beginning	of  an
	  expression permits a successful match only immediately after
	  a new-line, and the character $ at the end of an  expression
	  requires  a  trailing	 new-line.   The  character  /	in  an
	  expression indicates trailing context; only the part of  the
	  expression  up  to  the slash is returned in yytext, but the
	  remainder of the expression must follow in the input stream.
	  An  operator	character may be used as an ordinary symbol if
	  it is within " symbols or preceded  by  \.   Thus  [a-zA-Z]+
	  matches a string of letters.

	  Three subroutines defined as macros are expected: input() to
	  read	a character; unput(c) to replace a character read; and
	  output(c) to place an output character.  They are defined in
	  terms	 of  the  standard streams, but you can override them.
	  The program generated is  named  yylex(),  and  the  library
	  contains  a main() which calls it.  The action REJECT on the
	  right side of the rule causes this match to be rejected  and
	  the  next  suitable  match  executed;	 the function yymore()
	  accumulates additional characters into the same yytext;  and
	  the function yyless(p) pushes back the portion of the string
	  matched beginning at p, which should be between  yytext  and
	  yytext+yyleng.   The	macros input and output use files yyin
	  and yyout to read from and write to, defaulted to stdin  and
	  stdout, respectively.

	  Any line beginning with a blank is assumed to contain only C
	  text	and is copied; if it precedes %% it is copied into the
	  external definition area of the lex.yy.c  file.   All	 rules
	  should  follow  a  %%, as in YACC.  Lines preceding %% which
	  begin with a non-blank character define the  string  on  the
	  left	to  be the remainder of the line; it can be called out
	  later by surrounding it with {}.  Note that  curly  brackets
	  do not imply parentheses; only string substitution is done.

	  The flags, which  must  appear  before  any  files,  are  as
	  follows:

	       -r   indicates ratfor(1) actions;

	       -c   indicates C actions - this is the default;

	       -t   causes the lex.yy.c program to be written  instead
		    to the standard output;

	       -v   provides a one-line summary of statistics for  the
		    machine generated;

	       -n   suppresses printing of the - summary.

	  Certain table sizes for the resulting finite	state  machine
	  can be set in the definitions section:

	       %p n    number of positions is n (default is 2000);

	       %n n    number of states is n (default is 500);

	       %t n    number of parse tree nodes  is  n  (default  is
		       1000);

	       %a n    number of transitions is n (default is 3000).

	  The use of one  or  more  of	the  preceding	table  options
	  automatically implies -v, unless -n is specified.

	  External names generated by lex all begin with the prefix yy
	  or YY.

     EXAMPLE
		  D	  [0-9]
		  %%
		  if	  printf("IF statement\n");
		  [a-z]+  printf("tag, value %s\n",yytext);
		  0{D}+	  printf("octal number %s\n",yytext);
		  {D}+	  printf("decimal number %s\n",yytext);
		  "++"	  printf("unary op\n");
		  "+"	  printf("binary op\n");
		  "/*"	  {	  loop:
				  while (input() != '*');
				  switch (input())
					  {
					  case '/': break;
					  case '*': unput('*');
					  default: go to loop;
					  }
				  }

     SEE ALSO
	  yacc(1), malloc(3X).						*
	  LEX - Lexical Analyzer  Generator,  in  HP-UX	 Concepts  and
	  Tutorials.

     BUGS
	  The -r option is not yet fully operational.