lex.1

unix v7是最后一个广泛发布的研究型UNIX版本

.TH LEX 1 
.SH NAME
lex \- generator of lexical analysis programs
.SH SYNOPSIS
.B lex
[
.B \-tvfn
] [ file ] ...
.SH DESCRIPTION
.I Lex
generates programs to be used in simple lexical analyis of text.
The input
.I 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:
.IP
cc lex.yy.c \-ll
.LP
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 following 
.I lex
program converts upper case to lower,
removes blanks at the end of lines,
and replaces multiple blanks by single blanks.
.IP ""
.nf
.ta \w'[A\-Z] 'u
%%
[A\-Z]	putchar(yytext[0]+\'a\'\-\'A\');
[ ]+$
[ ]+	putchar(\' \');
.fi
.PP
The options have the following meanings.
.TP
.B \-t
Place the result on the standard output instead of in file
`lex.yy.c'.
.TP
.B \-v
Print a one-line summary of statistics of the generated analyzer.
.TP
.B \-n
Opposite of
.BR \-v ;
.B \-n
is default.
.TP
.B \-f
`Faster' compilation: don't bother to pack
the resulting tables; limited to small programs.
.SH "SEE ALSO"
yacc(1)
.br
M. E. Lesk and E. Schmidt,
.I LEX \- Lexical Analyzer Generator