LEX(1)
NAME
lex − generator of lexical analysis programs
USAGE
lex [ −tvfn ] [ file ] ...
DESCRIPTION
Lex generates programs for doing 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.
Lex generates a C source program, lex.yy.c, to be compiled in the following manner:
cc lex.yy.c −ll
This program copies unrecognized portions of the input to the output, and executes the associated C action for each regular expression 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 Do not print a statistical summary. This is the default.
−f Compile very quickly, not stopping to pack the resulting tables. This option is limited to small programs.
EXAMPLE
To draw lex instructions from the file lexcommands and place the output in the file lex.yy.c, execute the following:
lex lexcommands
The text below is an example of a lex program that you might put into a lex command file. This program converts uppercase to lowercase, removes blanks at the end of lines, and replaces multiple blanks by single blanks:
%%
[A−Z]putchar(yytext[0]+´a´−´A´);
[ ]+$
[ ]+putchar(´ ´);