LEX Program to count the number of lines, words and letters

Howdy guys,

Lets have a look on how a Lex programs works using a simple example.

This sample programs counts the number of lines, words and characters in a text file.

 

Lex programming is not rocket science. You have to just apply an eight year old kid's logic. Yes, you read right. Only a school kid's logic.

LOGIC

Read each character from the text file :

• Is it a capital letter in English? [A-Z] : increment capital letter count by 1.
• Is it a small letter in English? [a-z] : increment small letter count by 1
• Is it [0-9]? increment digit count by 1.
• All other characters (like '!', '@','&') are counted as special characters
• How to count the number of lines? we simply count the encounters of '\n' <newline> character.that's all!! 
• To count the number of words we count white spaces and tab character(of course, newline characters too..)

 Alignment of a Lex program is very simple and it makes the logic more vivid.

counter.l

%{

#include<stdio.h>

int lines=0, words=0,s_letters=0,c_letters=0, num=0, spl_char=0,total=0;

%}

%%

 

\n { lines++; words++;}

[\t ' '] words++;

[A-Z] c_letters++;

[a-z] s_letters++;

[0-9] num++;

. spl_char++;

%%

main(void)

{

yyin= fopen("myfile.txt","r");

yylex();

total=s_letters+c_letters+num+spl_char;

printf(" This File contains ...");

printf("\n\t%d lines", lines);

printf("\n\t%d words",words);

printf("\n\t%d small letters", s_letters);

printf("\n\t%d capital letters",c_letters);

printf("\n\t%d digits", num);

printf("\n\t%d special characters",spl_char);

printf("\n\tIn total %d characters.\n",total);

}

 

int yywrap()

{

return(1);

}

Sample output

 Let the 'myfile.txt' contains this.

                         This is my 1st lex program!!!

                         Cheers!! It works!!:)

The output will be

This file contains..

2 lines

9 words

30 small letters

3 capital letters

1 digits

9 special characters

In total 43 characters.

Posted in: Language processing programs , LEX Programs