C Program to Count Lines of Code

Question

I'm writing a simple LOC counter in C to count how many lines of code are in my C source files. It's meant to be run from the command line, redirecting the target file as input and seeing a total line count printed to standard out. For example:

  counter.exe < counter.c
  15

So far the only rules I'm using are:

Only count lines that have more than 3 characters (no blank lines or lines that only have a closing brace and semi-colon, etc).
Don't count spaces as characters.

Here's my program:

#include <stdio.h>

int main() {

    int input;
    int linecount = 0;
    int charcount = 0;

    while ((input = getchar()) != EOF) {

        if (input == ' ') {
        }
        else if (input == '\n') {
            if (charcount > 3) {
               linecount++;
            }
            charcount = 0;
        }
        else {
            charcount++;
        }
    }

    printf("%d\n", linecount);

    return 0;
}

My question is, can you offer some improvements to the rules to make this a more valid measure? Do people often count comments as valid lines of code? How about spaces or blank lines?

I don't want to start a debate over the validity of LOC counts in general, it's something I've been asked in several interviews and I think is worth knowing, in a general sense, how many lines of code my own projects are. Thanks!

I wouldnt worry so much about counting the lines of code, it is in my experience irrelevant. Something which counted the quality of code on the other hand... — Mick Walker, Mar 11 '11 at 16:03
I have to agree. You could even argue that a smaller line count is better, if it has the same functionality and is easy to understand by others. But again I'm interested in this because I was asked this during an interview question (how many lines of code would you say were in the largest project you've personally worked on?) I drew a blank, I really couldn't even come up with a guess. So this is a programming exercise and also just to get a deeper understanding of what a LOC count might be useful for. Thanks again. — dvanaria, Mar 11 '11 at 16:20
Just a comment on the code itself: if you find yourself writing an empty if statement, this means there is usually a better way to structure your if's. Ex. `if (input == '\n') { ... } else if (input != ' ') { ... }` — MahlerFive, Mar 11 '11 at 16:46

score 7 · Accepted Answer · answered Mar 11 '11 at 16:00

7

Generally, people do:

Count comments as LOC
Count blank lines as LOC

However, people also assume/practice:

Comments included are necessary/useful (not gratituitous)
Blank lines are not excessive, and exist to provide clarity

Code line counters, as a result, generally take into account all line breaks in their computation.

answered Mar 11 '11 at 16:00

kvista

5,039
1
23
25

+1 for "Comments included are necessary/useful (not gratituitous)" – Sagar Mar 11 '11 at 16:02

score 6 · Answer 2 · edited Jan 09 '12 at 22:48

6

Don't write a program. Use wc --lines

edited Jan 09 '12 at 22:48

Devin Burke

13,642
12
55
82

answered Mar 11 '11 at 15:58

user654241

79
3

@Raveline: So will OP's program. – nmichaels Mar 11 '11 at 16:03
Thanks, I was doing this more as a programming exercise though. I agree, normally an existing tool would be preferred. – dvanaria Mar 11 '11 at 16:04
2

Combine with variations of `grep -v` to skip blank lines, short lines, and comments as desired. – nmichaels Mar 11 '11 at 16:04

score 2 · Answer 3 · answered May 21 '13 at 10:57

2

I realise this was a programming example, but if you want to use a windows command line I found this.

Which lead to:

findstr /R /N "^" *.h *.c | find /C ":"

Counts all lines in .h and .c files.

answered May 21 '13 at 10:57

weston

54,145
21
145
203

score 1 · Answer 4 · answered Mar 11 '11 at 17:22

I guess I came from a different development style than kvista, but we counted lines of code and comments separately. We expected that the comments would be a certain percentage of the total lines (comments + code). We didn't count blank lines at all.

If you're looking for a bit of a programming challenge, you can measure the cyclomatic complexity (or conditional complexity) of your C programs.

score 0 · Answer 5 · answered Mar 11 '11 at 20:36

Make a schedule of how long it will take you to write and debug the application. Note the ending date.

Spend some time searching the web for tools such as:
http://www.campwoodsw.com/sourcemonitor.html

Take the remaining time in your schedule and go on vacation. :-)

Otherwise the task becomes monstrous. Such as parsing comments. Defining a line (and how many statements or tokens are on a line). Are blank lines counted?

Save your precious time for other projects. Use existing tools.

C Program to Count Lines of Code

5 Answers5