segmentation fault??

i'm trying to write a program that accepts three strings: text, s, and r. The function searches string text for string s. if it finds string s, it should replace it with string r. i wrote all the code and it compiles but when i try and run it stops and says "segmentation fault"

i know it's something with my pointers but i can't figure it out for the life of me. i could definitely use some help...thanks

Code:

#include <stdio.h>
#include <string.h>
        
#define MAX 100
char search_and_replace(char *text,char *s, char *r);
         
int main(void)
{                
        
        char *text[MAX];
        char *s[MAX];
        char *r[MAX];
 
        /* Find text string */
        printf("Please enter a text string.\n");
        gets(*text);

        /* Find the search string */
        printf("Please enter a search string.\n");
        gets(*s);
        
        /* Find the replacing string */
        printf("Please enter a replace string.\n");
        gets(*r);
       
        search_and_replace(*text, *s, *r);
                 
        return(0);
        }
                 
char search_and_replace(char *text, char *s, char *r)
{

int next;
char length_text;
char length_s;
char diff;

        
        length_text = strlen(text);
        length_s = strlen(s);
        diff = length_text - length_s; 
        
        for(next = 0; next <= diff; ++next);
        {
                if(strncmp(&text[next], s, length_s) == 0)
                {
                strcpy(&text[next], r);
                printf("%s", text);
                }
        }
 
return(0);

}

1. don't use gets - see FAQ
2. char *text[MAX]; is just an array of pointers to char that point nowhere
*text is a first pointer, that points nowhere... when you try to write something (using gets) to unknown location - behaviour is undefined. 2 most probable results - you get an protaction fault due to the random address is outside your address space - or you overwrite some valuable data of your program that will cause the crash when you read this data.

i'm still confused as to how to get rid of the segmentation fault. if i take out the pointers, the program doesn't compile

you should write to the memory you own
if you want to store several strings - use 2-dimentional array, not array of pointers

or dynamically allocate memory fro every pointer

i try and just use scanf to take the strings but it gives me the same segment error

Originally Posted by snappleapple

i try and just use scanf to take the strings but it gives me the same segment error

You try what? post your new code

I'm really really confused by c's little technicalities. when i use scanf like this it lets me enter in the first string but not the second and third strings

Code:

int main(void)
{
  
        char *text[MAX];
        char *s[MAX];
        char *r[MAX];
  
        /* Find text string */
        printf("Please enter a text string.\n");
        scanf("%s", &text);
   
        /* Find the search string */
        printf("Please enter a search string.\n");
        scanf("%s", &s);

        /* Find the replacing string */
        printf("Please enter a replace string.\n");
        scanf("%s", &r);

        /*Performs program task*/
        search_and_replace(*text, *s, *r);

        return(0);

Remove the stars, Luke.

getting rid of the stars gives me this:

Code:

kkeyser@shellfish:~/CPrograms> gcc search-replace.c
search-replace.c: In function `main':
search-replace.c:40: warning: passing arg 1 of `search_and_replace' makes pointer from integer without a cast
search-replace.c:40: warning: passing arg 2 of `search_and_replace' makes pointer from integer without a cast
search-replace.c:40: warning: passing arg 3 of `search_and_replace' makes pointer from integer without a cast

All of them in main

Like
char s[MAX];

fgets( s, sizeof s, stdin );

myfunc( s );