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 expressions are found. 

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

cc lex.yy.c −ll

This program copies unrecognized portions of the input to the output, and executes the associated C action for each recognized regular expression. 

The following lex program converts upper case to lower case, removes blanks at the end of lines, and replaces multiple blanks by single blanks. 

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

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 analyzer. 

−n Opposite of −v; −n is default. 

−f ‘Faster’ compilation: do not bother to pack the resulting tables; this option is limited to small programs. 

SEE ALSO

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

October 26, 1983  —  %W%