find a string

Hi!I'm new to C programming and I wanted to ask where is the error in this code:
I have a file text ( frase.txt),placed in the same folder and I have to search for a string in this text and if I find that string I have to print it.

Code:

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


int main(){
const char searchingString[20];
FILE *fillle= fopen("frase","r");

char *s;
char *token;
printf("Introduce the string:");
scanf("%s",searchingString);

while(fgets(s,128,fillle)!=NULL){

token = strtok(s ," ");

if(strcmp(token,searchingString) == 0)
printf("%s\n",searchingString);
else printf("0\n");
while (strtok!=NULL) {
token= strtok(NULL," ");
if(strcmp(token,searchingString) == 0)
printf("%s\n",searchingString);
else printf("0\n");
}
}
}

When I compile the file it doesn't give me any problem and when I try the program it prints on the monitor Introduce the string,but when I give it it says segmentation fault!
What's the problem?thanks!

Sorry for my English!

Code:

char *s;  // This pointer is uninitialized. 
. . .
fgets(s, 128, fillle);  // You're using an uninitialized pointer.

Why declare searchstring as const when you don't want it to be constant!
's' is pointer to char and you are using it without initializing.
Change it to

Code:

char s[WHATEVER_SIZE_YOU_WANT];
  /*  or */
s = malloc( WHATEVER_SIZE_YOU_WANT);      // don't forget to free when you're done!

strictly s = malloc( sizeof(*s) * WHATEVER_SIZE_YOU_WANT);

I've changed my code as you've said,but it stills give me the same problem..

Code:

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

int main(){
char searchingString[20]; 
FILE *fillle= fopen("frase","r");
char s[512];
char *token;
printf("Introduce the string:");
scanf("%s",searchingString);
while(fgets(s,512,fillle)!=NULL){
token = strtok(s ," ");
if(strcmp(token,searchingString) == 0)
printf("%s\n",searchingString);
else printf("0\n");
while (strtok!=NULL) {
token= strtok(NULL," ");
if(strcmp(token,searchingString) == 0)
printf("%s\n",searchingString);
else printf("0\n");
}
}
}

strtok != NULL is always true. Perhaps you mean to check while token != NULL -- although, even then, you're one step too late since you use the new value of token before checking it.

Also read this - SourceForge.net: Indentation - cpwiki

Your code is only 20 lines long (or so), and already it is very hard work to follow what is going on.

Also, use int main(void) and return 0 at the end of main.