C++ Cookbook

4.17. Counting the Number of Characters, Words, and Lines in a Text File

Problem

You have to count the numbers of characters, words, and lines—or some other type of text element—in a text file.

Solution

Use an input stream to read the characters in, one at a time, and increment local statistics as you encounter characters, words, and line breaks. Example 4-26 contains the function countStuff, which does exactly that.

Example 4-26. Calculating statistics about a text file

#include <iostream>
#include <fstream>
#include <cstdlib>
#include <cctype>

using namespace std;

void countStuff(istream& in,
                int& chars,
                int& words,
                int& lines) {

   char cur = '\0';
   char last = '\0';
   chars = words = lines = 0;

   while (in.get(cur)) {
      if (cur == '\n' ||
          (cur == '\f' && last == '\r'))
         lines++;
      else
        chars++;
      if (!std::isalnum(cur) &&   // This is the end of a
          std::isalnum(last))     // word
         words++;
      last = cur;
   }
   if (chars > 0) {               // Adjust word and line
      if (std::isalnum(last))     // counts for special
         words++;                 // case
      lines++;
   }
}

int main(int argc, char** argv) {

   if (argc < 2)
      return(EXIT_FAILURE);

   ifstream in(argv[1]);

   if (!in)
      exit(EXIT_FAILURE);

   int c, w, l;

   countStuff(in, c, w, l);
1
   cout << "chars: " << c << '\n';
   cout << "words: " << w << '\n';
   cout << "lines: " << l << '\n';
}

Discussion

The algorithm here is straightforward. Characters are easy: increment the character count each time you call get on the input stream. Lines are only slightly more difficult, since the way a line ends depends on the operating ...