lex(1)

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. 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

In the following example, the command

lex lexcommands

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

%%
[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.

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