LEX(1) — User’s Manual — Commands

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 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.

OPTIONS

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

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