usr/src/old/lex/lex.1

.\" Copyright 1991 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" %sccs.include.proprietary.roff%
.\"
.\"     @(#)lex.1       6.3 (Berkeley) %G%
.\"
.Dd
.Dt LEX 1
.Os ATT 7th
.Sh NAME
.Nm lex
.Nd generator of lexical analysis programs
.Sh SYNOPSIS
.Nm lex
.Op Fl tvfn
.Op Ar file
.Ar ...
.Sh DESCRIPTION
The
.Nm lex
command
generates programs to be used in simple lexical analyis of text.
The input
.Em files
(standard input default) contain regular expressions
to be searched for, and actions written in C to be executed when
expressions are found.
.Pp
A C source program, 'lex.yy.c' is generated, to be compiled thus:
.Bd -literal -offset indent
cc lex.yy.c.Fl ll
.Ed
.Pp
This program, when run, copies unrecognized portions of
the input to the output, and executes the associated
C action for each regular expression that is recognized.
.Pp
The options have the following meanings.
.Bl -tag -width indent
.It Fl t
Place the result on the standard output instead of in file
.Pa lex.yy.c .
.It Fl v
Print a one-line
summary of statistics of the generated analyzer.
.It Fl n
Opposite of
.Fl v ;
.Fl n
is default.
.It Fl f
"Faster" compilation: don't bother to pack
the resulting tables; limited to small programs.
.Sh EXAMPLE
.Bd -literal -offset indent
lex lexcommands
.Ed
.Pp
would draw
.Nm lex
instructions from the file
.Pa lexcommands ,
and place the output in
.Pa lex.yy.c
.Bd -literal -offset indent
%%
[A.Em \-Z] putchar(yytext[0]+\&'a\&'\-\&'A\&');
[ ]+$   ;
[ ]+    putchar(\&' \&');
.Ed
.Pp
is an example of a
.Nm lex
program that would be put into a
.Nm lex
command file.  This program converts upper case to lower,
removes blanks at the end of lines,
and replaces multiple blanks by single blanks.
.Sh SEE ALSO
.Xr yacc 1 ,
.Xr sed 1
.Rs
.%A M. E. Lesk
.%A E. Schmidt
.%T "The LEX \- Lexical Analyzer Generator"
.Re