CODEWITHSUNDEEP
csegmentation-fault
laxantsu
laxantsu

Reputation: 15

Segmentation fault (core dumped) when not using arguments

I could be doing this completely the wrong way, but considering this will be for personal use, having it not be that efficient is okay.

When ran as ./todo -r, it works.

When ran as ./todo -a, it works.

When ran as ./todo, it gives me segmentation fault (core dumped)

#include<stdio.h>
#include<stdlib.h>

int main(int argc, char *argv[]) {

    if(argc < 1) {
    printf("Not enough variables.");
    }

    if(strcmp("-r",argv[1])==0) {
        printf("\n");

        system("cat .todo");
        printf("\n");
    }
    if(strcmp("-a",argv[1])==0)   {
    char str[BUFSIZ];
    FILE *f;
    f = fopen(".todo","a");
    printf("\n\nTODO list\n\n");
    for(;;) {

        printf("~ ");
        fgets(str,256,stdin);
        if(strcmp(str,"\n")==0) {
            fclose(f);
            printf("\n");
            break;
        }

        fprintf(f,str);
        }
    return 0;
    }
}

Upvotes: 0

Views: 998

Answers (3)

Roddy
Roddy

Reputation: 68033

argv[0] is the program executable name, and it's counted towards argc.

So ./todo has argc=1, but argv[1] is NULL, which will cause a problem for strcmp().

See argv[argc] ==?

Change your test:-

if (argc < 2) 
{
  printf("Not enough variables.");
  return 0; // do this, otherwise we'll plough straight on..
}

Upvotes: 2

Ken Wayne VanderLinde
Ken Wayne VanderLinde

Reputation: 19339

As others have pointed out, you need argc < 2 rather than argc < 1.

Additionally, you probably want to return from the if, to stop the rest from executing:

if(argc < 2) {
  printf("Not enough variables.");
  return /* some appropriate value here */;
}

Upvotes: 1

Marc B
Marc B

Reputation: 360602

You're closing your file handle and then still trying to write to it:

if (...) {
   fclose(...); <--potentially closing it, depending on the if() results
}
fprintf(...); <--potentially writing to a closed handle.

This is a BAD idea.

Upvotes: 0

Related Questions