Question

I get a Segmentation fault inside the insert function within the printf statment

#include <stdio.h>
#include <stdlib.h>
void Insert(char w[])
{
int j;
int n=5;
printf("word is %s AFTER\n", w);
}


int main(int argc, char *argv[])
{
        FILE *fp;
        if (argc !=2)
                fp=fopen("words.txt", "r");
        else
                fp=fopen(argv[1], "r");
        char line[28];
        while(!feof(fp)){
                fgets(line, 256, fp);
                Insert(line);
        }
}

in word.txt its just a bunch of words on each line i.e.

apple
banana
...
zoo

(… just means a bunch of words in between)
it prints this:

word is apple
AFTER
word is banana
AFTER
...(a bunch more repetitions)                                    
word is cookie
Segmentation Fault(core dumped)

Why is there a segmentation fault? it printed the word perfectly. And it didn’t print the AFTER

Thanks.

Answer 1

Allocated memory only 28 bytes where as trying to copy 256 byte.

char line[28]; <-- 28 bytes only allocated to line.
        while(!feof(fp)){
                fgets(line, 256, fp); <-- 256 bytes read into line.

Increase the memory for line to avoid this issue.