checking for a code in a string

Hi guys i am encountering some problems.

I need to write a prog that compares a user input string with a code wode, if the code word is found, the program will return the positions of the code word found in the user input string. I manage to done part if i already fixed the code word in my prog, but somehow if i allow the user to input the code word to check for, the prog doesn't work as i have fixed the code word to 3 letters, is there a way where i can get the prog to check for any length of letters?

Obvious answer is don't limit the code word to three letters.

You'll need some "large enough" buffer (256 characters, perhaps).

How are you currently doing it? You might try strstr().

current code is as follows:

Code:

---

main()
{
      char string1[100];
      char string2[]="ABCD";
      int i,n;
      printf("Please enter a string : ");
      scanf("%s",string1);
      n=strlen(string1);
      for(i=0;i<=n;i++)
      {
                      if((string1[i]==string2[0]) && (string1[i+1]==string2[1]) && (string1[i+2]==string2[2]) && (string1[i+3]==string2[3]))
                      printf("\nCode found at %d", i+1);
      }
     
      system("pause");
                   
}

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if i want to let the user to enter the code word, any idea how it can be done?

Code:

---

n=strlen(string1);
for(i=0;i<=n;i++)

---

This for loop is dangerous. Say the string is "helloz." strlen(string1) will return 7. However, string1[7] is out of bounds.

This link may be helpful. Make sure you try and learn from it, though.

Quote:

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Originally Posted by kpreston

Code:

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n=strlen(string1);
for(i=0;i<=n;i++)

---

This for loop is dangerous. Say the string is "helloz." strlen(string1) will return 7. However, string1[7] is out of bounds.

This link may be helpful. Make sure you try and learn from it, though.

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don't really get it as i didn't learn address pointer before..

Quote:

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Originally Posted by shin_ono

don't really get it as i didn't learn address pointer before..

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I don't have sufficient knowledge in the language to actually teach you. I'm just trying to point you in the right direction, so you can do your own research.

thanks man, i will try it out

> This for loop is dangerous. Say the string is "helloz." strlen(string1) will return 7. However, string1[7] is out of bounds.
Actually it's not.

string1[7] is going to be the nul terminator. And don't say "what if there isn't one", because then strlen() would segfault. :)

I take it that using strstr() wouldn't be allowed.

Quote:

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Originally Posted by zacs7

> This for loop is dangerous. Say the string is "helloz." strlen(string1) will return 7. However, string1[7] is out of bounds.
Actually it's not.

string1[7] is going to be the nul terminator. And don't say "what if there isn't one", because then strlen() would segfault. :)

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My mistake. Thank you for correcting me. But in my defense, there's no reason to compare the null terminator. :(

> there's no reason to compare the null terminator.
There certainly isn't... good pickup none-the-less.

I think its best not to use strstr?

can get the program to check for number of times the code (user input)..
anyone can help?

I must also point out: http://cpwiki.sourceforge.net/Implicit_main
And reading strigs with scanf: (See signature)