Question

I am passing a txt file as command line argument and displaying it contents to the stdout. I want to create 5 integer variables (n,a,b,i,temp) at the start of the program. But the program is giving me a segfault once I declare more than 2 integers. If I comment out the third int declaration (int b), the program is running fine. Also, I am running on ubuntu.

main(int argc, char *argv[]){
    int n;
    int a;
    int b;
//  int i;
//  int temp;
    char *s;
    if(argc!=2){
            printf("not enough arguments provided!!\n");
            exit(-1);
    }
    FILE *fp = fopen(argv[1],"r");
    while((s=fgets(s,5,fp))!=NULL){
            n = atoi(s);
            printf("%d",n);
}
    fclose(fp);
}

Answer 1

Your fgets(s,5,fp) reads into an uninitialized pointer. You have to allocate storage which you place the read data into.

Change char *s; to char s[5];

Edit: Also change your while loop condition:

while(fgets(s,5,fp)) {

You should also check whether fopen() succeeds or fails.