trouble with strstr

This is a discussion on trouble with strstr within the C Programming forums, part of the General Programming Boards category; I'm trying to write a spam checker using strstr, but I'm having trouble getting it to work properly. I want ...

  1. #1
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    trouble with strstr

    I'm trying to write a spam checker using strstr, but I'm having trouble getting it to work properly. I want it to increment the counter when it finds a match, then if 2 or more matches are found to report spam. However it is incrementing when any word/phrase other then the compare string is entered. It also doesn't print the "no spam" message regardless of what is entered. Here is what I have got so far:
    Code:
    #include <stdio.h>
    #include <string.h>
    
    int main (void)
    {
        char input[128];
        int counter;
      
        counter = 0;
    
        fgets (input, sizeof(input), stdin);
    
        if (strstr(input, "free car") != NULL)
            counter = counter +1;
    
         else
            if (strstr(input, "credit") != NULL)
            counter = counter +1;
    
         else
            if (counter = 2)
            printf( "message contains spam\n" );
              else
              printf( "no spam found\n" );    
            
    
    }

  2. #2
    C++ Witch laserlight's Avatar
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    There is a difference between = and ==. Also, check your logic.
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  3. #3
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    Ok so I got it to properly report when no spam keywords are found by using
    Code:
    if (counter == 2)
    but I still can't get it to report spam. I changed the printf statements to show the counter totals to try and figure out what its doing. I get nothing when is enter the spam strings and "counter = 68004" when I enter any non spam. I'm not sure what I'm doing wrong.

  4. #4
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    Code:
    counter = 0;
    fgets (input, sizeof(input), stdin);
    
    
    if (strstr(input, "free car") != NULL)
        counter = counter +1;
    
    else if (strstr(input, "credit") != NULL)
        counter = counter +1;
    
    else if (counter = 2) /* == already corrected */
        printf( "message contains spam\n" );
    
    else
        printf( "no spam found\n" );
    Here is your code from post #1. I restructured it (by changing whitespace - the code is exactly the same) to help you see how the logic is flowing.

    Note that your program contains no loops, so it will run through "main()" once and exit.

    So, if the first condition on (line 5) is true, you increment counter - but then everything else in the program is skipped. That is how an "if-else" chain works. The same with all the other "if()" statements. Do you see that now it in the code I posted?

  5. #5
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    Yes that helps, thanks.

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