Question

#include <stdio.h>
#include <string.h>

int main() {
  char tab[2]={"12"};
  FILE *outfile;
  char *outname = "/home/dir/";
  printf("%s", strcat(outname,tab));
  outfile = fopen(strcat(outname,btab), "w");
  if (!outfile) {
    printf("There was a problem opening %s for writing\n", outname);
  }
}

I have this error: Segmentation Fault.

How can I fix it?

Answer 1

At least two errors:

char tab[2] = {"12"};

You’d better use tab[3] or even better tab[] — you need one extra char for the terminating NUL character.

Also,

char *outname = "etc...";

creates a constant string in the data segment of the executable — it can’t be overwritten, since strcat is using its first parameter to concatenate the two strings. So when strcat() tries to do so, it segfaults. Use

char outname[50]; // something big enough
strcpy(outname, "/home/dir");

instead.