CODEWITHSUNDEEP
csegmentation-faultword-count
Charlie Owen
Charlie Owen

Reputation: 11

Word Count, Segmentation Fault - C

I'm trying to run a program that finds the word count for a file. Every time I compile the program it gives me a Segmentation Fault(Core Dumped). Can't figure out why.

#include <stdio.h>

int main(int argc, char* argv[]){
    int wc = 1;
    FILE *input = fopen(argv[1],"r");
    char c = fgetc(input);
    while(c != EOF){
        if(c == ' '){
            wc++;
        }
        else
            c = fgetc(input);
    }
    fclose(input);
    printf("Word Count = %d", wc);

return 0;
}

Upvotes: 0

Views: 197

Answers (1)

dbush
dbush

Reputation: 224102

You're probably segfaulting because you're not passing in a file name on the command line. When you do that, argv[1] is NULL, so fopen is dereferencing a NULL pointer.

You pass the file name to your program on the command line like this:

./my_program file_to_test

To prevent the core dump, you should check that an argument was passed in by checking the value of argc. You should also check the return value of fopen to ensure the file was opened:

if (argc < 2) {
    printf("no file name given");
    exit(1);
}
FILE *input = fopen(argv[1],"r");
if (input == NULL) {
    perror("fopen failed");
    exit(1);
}

Then you have another problem:

    if(c == ' '){
        wc++;
    }
    else
        c = fgetc(input);

When you find a space character, you don't attempt to read the next character. So c doesn't change once a space is read, leading to an infinite loop.

You need to get rid of the else and always call fgetc:

    if(c == ' '){
        wc++;
    }
    c = fgetc(input);

Also, the fgetc function returns an int (actually an unsigned char cast to an int), so you should declare c as an int. Otherwise, checking it against EOF can fail.

Upvotes: 1

Related Questions