4.3BSD - /usr/man/cat1/lex.0

LEX(1)                                                                  LEX(1)


NAME
       lex - generator of lexical analysis programs

SYNOPSIS
       lex [ -tvfn ] [ file ] ...

DESCRIPTION
       Lex  generates  programs  to be used in simple lexical analyis of text.
       The input files (standard input default) contain regular expressions to
       be  searched  for, and actions written in C to be executed when expres‐
       sions are found.

       A C source program, ’lex.yy.c’ is generated, to be compiled thus:

              cc lex.yy.c -ll

       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.

       The options have the following meanings.

       -t     Place the result on the  standard  output  instead  of  in  file
              "lex.yy.c".

       -v     Print  a  one-line  summary  of statistics of the generated ana‐
              lyzer.

       -n     Opposite of -v; -n is default.

       -f     "Faster" compilation: don’t bother to pack the resulting tables;
              limited to small programs.

EXAMPLE
              lex lexcommands

       would  draw  lex  instructions from the file lexcommands, and place the
       output in lex.yy.c


              %%
              [A-Z] putchar(yytext[0]+�´a�´-�´A�´);
              [ ]+$ ;
              [ ]+  putchar(�´ �´);

       is an example of a lex program that would be put  into  a  lex  command
       file.  This program converts upper case to lower, removes blanks at the
       end of lines, and replaces multiple blanks by single blanks.

SEE ALSO
       yacc(1), sed(1)
       M. E. Lesk and E. Schmidt, LEX - Lexical Analyzer Generator


7th Edition                     April 14, 1986                          LEX(1)