NAME

lex − generator of lexical analysis programs

SYNTAX

lex [ −tvfn ] [ file... ]

DESCRIPTION

The lex command generates programs to be used in simple lexical analysis of text.  Each input file (standard input default) contains regular expressions to be searched for, and action statements (written in C) to be executed when expressions 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 following lex program converts upper case to lower, removes blanks at the end of lines, and replaces multiple blanks by single blanks. 

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

OPTIONS

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

−n Opposite of −v; −n is default. 

−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. 

SEE ALSO

yacc(1)
“LEX − Lexical Analyzer Generator”