Thread: I can not write a value into an array of strings

My program:

Code:

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

char *pins[1][1777];

int load(char *name)
{
   FILE *f;
   f = fopen(name, "r");
   if(f == NULL) return -1;
   char str[8];
   char *tmp;
   int i=0;
   while( fgets(str, 9, f) != NULL)
   {
      if(str[0] == '\n') continue;
      tmp = str;
      pins[0][i] = tmp;
      i++;
}
   return 0;
}

int main(int argc, char *argv[])
{
   if(argc != 3) { printf("Usage: %s [file] [mac]\n", argv[0]); return 1; }
   if(load(argv[1]) == -1) {
      printf("Error load file\n"); return 1;
   }

   char cmd[100];
   for(int i=0; i<1777; i++)
   {
      sprintf(cmd, "wpa_cli wps_reg %s %s", argv[2], pins[0][i]);
      printf("%s\n", cmd);
   }
   return 0;
}

I ran the program and saw such rubbish:

Code:

wpa_cli wps_reg s @�Ϫ�
wpa_cli wps_reg s @�Ϫ�
wpa_cli wps_reg s @�Ϫ�
wpa_cli wps_reg s @�Ϫ�
wpa_cli wps_reg s @�Ϫ�
wpa_cli wps_reg s @�Ϫ�
wpa_cli wps_reg s @�Ϫ�
wpa_cli wps_reg s @�Ϫ�
wpa_cli wps_reg s @�Ϫ�
wpa_cli wps_reg s @�Ϫ�
wpa_cli wps_reg s @�Ϫ�
wpa_cli wps_reg s @�Ϫ�
wpa_cli wps_reg s @�Ϫ�

And each launch displays a different nonsense!
I replaced these lines:

Code:

tmp = str;
      pins[0][i] = tmp;

on:

Code:

sprintf(pins[0][i], "%s", str);

And the segmentation error comes out!I read a book on it, but there it was not taught to me on any page for the whole book, and how to work with strings in C if it is so difficult?
In general, help me to solve this problem !!

On line 4 you declare an array for 1 string hat cold hold 1777 chars - I guess that's not what you actually want.
On line lines 11 + 14. str has space for 7 chars + terminating '\0', but on line 14 you try to read 9 chars into it.
Another problem is on line 18. pins[0][i] can hold a single char but you try to store more in it.

Yes, strings are error prone in C. In C++ you have strings which are much easier to use. If you have a choice switch to C++.