c count lines in a file avoid EOF

Question

On numerous sources, you can find a simple C program to count the number of lines in a file. I'm using one of these.

#include <stdio.h>


int main(int argc, char* argv[]) {   
    FILE *file;
    long count_lines = 0;
    char chr;
 
    file = fopen(argv[1], "r");
    while ((chr = fgetc(file)) != EOF)
    {
        count_lines += chr == '\n';
    }
    fclose(file); //close file.
    printf("%ld %s\n", count_lines, argv[1]);
    return 0;
}

However, it fails to count the num. of lines in Top2Billion-probable-v2.txt. It stops on the line

<F0><EE><E7><E0><EB><E8><FF>

and outputs

1367044 Top2Billion-probable-v2.txt

when it should output 1973218846 lines. wc -l somehow avoids the problem (and is amazingly faster).

Should I give up with a correct C implementation of counting the number of lines of a file or how should I space the special characters as wc does?

`chr` needs to be an int, not a char. See http://c-faq.com/stdio/getcharc.html — Shawn, Jul 04 '20 at 11:26
`fgetc` does not return a `char` but an `int`. How would you be able to distinguish a `0xFF` from an `` with a `char`? — Gerhardh, Jul 04 '20 at 11:26
Also try opening the file with `"rb"` instead of just `"r"`. `wc` is probably faster because it reads in larger blocks of data instead of individual characters, and searches these using optimized functions such as `strchr`. — Erlkoenig, Jul 04 '20 at 11:29
You're right. I should have used `int` that solves the issue. — dizcza, Jul 04 '20 at 11:44
And this is strange that typical internet solutions, at least those that I googled, don't mention the caveat that `chr` should be `int` and not a char. — dizcza, Jul 04 '20 at 11:52

score 0 · Accepted Answer · answered Jul 04 '20 at 15:10

0

fgetc() returns the character read as an unsigned char cast to an int or EOF. Hence declaring chr as int instead of char should solve the issue.

answered Jul 04 '20 at 15:10

ganjaam

1,030
3
17
29

c count lines in a file avoid EOF

1 Answers1