Thread: Trying to use strstr

That's because the first argument is not a STRING, but a character (and really an integer). So the compiler is telling you exactly what the problem is.

Originally Posted by fxtdr79

Could you tell me what to change where to fix it? Maybe it seems obvious to someone who knows what they're doing but Im totally lost.

I believe that your confusion stems from the fact that you don't really understand the difference between a character and a string.

A string is an array of characters. Your checkString function is actually taking as parameter a single character. So you can call checkString('b'); but you can't call checkString("hello") and expect to get the result you want. In C:

'b' is a character
"b" is string.

The function strstr works on strings not characters (i.e. finds where a substring occurs in another string). You should change the parameter type you are passing to that function to a char*. Then, in main you can allocate memory for an array of chars, and pass the pointer to that array to the checkString function like so:

Code:

/* allocate a string of 100 characters and make ptr_to_string point to that memory location*/
char *ptr_to_string = malloc(sizeof(char) * 100); 
/* copy something in the string */
strcpy(ptr_to_string, "Hello World");
/* find where the word "World" appears */
char *find = strstr(ptr_to_string, "World");

Originally Posted by fxtdr79

Thanks for trying claudiu but you've answered my question with an example of code that I don't know what to do with. I don't see how putting a fixed string with Hello World will help nor where to put it, but thanks for trying anyways.

You can JUST READ a string instead of reading character by character. Then, pass THE STRING YOU READ to the checkString function and change it's prototype to:

checkString(char *string_to_be_checked);

I can't be more clear than this.

To sum things up:

1) Learn to read a STRING from the console like Subsonics suggested.

2) Change the function checkString prototype to what has been suggested.

This should take you literally 2 minutes.

Originally Posted by fxtdr79

Here is my new code based on all the suggestions. Obviously I'm too stupid to figure this out. Since it should take 2 minutes and its taken me way too long.

Code:

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

void checkString(char c);

int main()
{
   char c[50];
   fgets(c, 50, stdin);

   while (c != EOF)
   {
      checkValue(c);
      c = getchar();
   }
   return(0);
}

void checkString(char *c)
{
   char *ptr_to_string = malloc(sizeof(char) * 100);
   strcpy(ptr_to_string, *c);
   char *find = strstr(ptr_to_string, "lb");
   if (*find != null)
   {
      puts("Input contains lb");
   }
}

First of all you are not stupid! You are just frustrated, relax, you will feel better once this works, because it will be YOUR WORK NOT MINE. I meant it should take two minutes to make some changes and post it back, which is what you did in that exact time frame. Take a deep breath, let the anger out, relax!

Now back to work:

A few things to fix now so you have a clean framework:

1) Do you see the checkString function declaration above the main() function? It still has the old argument type char c instead of char *c. That is basically telling main: "Hey if you see checkString anywhere this is what it should look like and its argument should pe a pointer. So if you leave it as it is the compiler will give you the same warning you got before basically saying : "hey, you told me this is supposed to take a character, but you are passing the argument as a pointer! STOP DECEIVING ME!! "

2) Delete everything in checkString and do what you were trying to do before with strstr() (not exactly sure what you were checking but you CAN NOW USE strstr, because c is now a pointer to string).

3) Delete the while loop you have in main now. fgets actually returns NULL if it fails so what you want is to while loop like this:

Code:

/* read until there is nothing left */
while(fgets(c,50,stdin) != NULL){
   /* do stuff with array c*/
}

Originally Posted by fxtdr79

Obviously I'm stupid. I guess that's why I haven't figured it out yet. If I can't use char for an array to represent a string, what else can I use?

You've got the magic word there: array. Why not use an array to represent your string? EDIT: To be more specific, you have to change everything to be an array.