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strcmp()

This is a discussion on strcmp() within the C Programming forums, part of the General Programming Boards category; I'm having trouble with strcmp(). I've read a topic on it, but couldn't understand. I'm using strcmp to compare a ...

  1. #1
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    strcmp()

    I'm having trouble with strcmp(). I've read a topic on it, but couldn't understand.


    I'm using strcmp to compare a variable (that comes from fgets-sscanf pair) with the string "DATA" and others.

    I declared the variable as char, and already tried to put a limit on the number of characters of the variable both on strcmp and on the declaration of the variable, but it still doesn't work.
    Could you give me some help?

    Here is the code segment:

    Code:
    void leitura(char linha[200], info informacao){
    
    
        char verifica;
    
    
        /*Usa-se if e [strcmp] para verificar sscanfs*/
    
    
        sscanf(linha,"%s",&verifica);
    
    
        if(strcmp(verifica[4],"DATA")==0){
    
    
            sscanf(linha,"DATA %d %d %d\n",&informacao.dia,&informacao.mes,&informacao.ano);
            informacao.aviso=1;
        
                    }
    
    
        if(strcmp(verifica[4],"AREA")==0){
    
    
            sscanf(linha,"AREA %d %d %d %d\n",&informacao.x1,&informacao.y1,&informacao.x2,&informacao.y2);
            informacao.aviso=2;
                    }
    
    
        if(strcmp(verifica[9],"INDIVIDUO")==0){
    
    
            sscanf(linha,"INDIVIDUO %d %d %d %d\n",&informacao.especie,&informacao.individuo,&informacao.x_individuo,&informacao.y_individuo);
            informacao.aviso=3;
                        }
    
    
        if(strcmp(verifica[7],"COLONIA")==0){
    
    
            sscanf(linha,"COLONIA %d %d %d %d %d\n",&informacao.especie_col,&informacao.colonia,&informacao.tamanho,&informacao.x_colonia,&informacao.y_colonia);
            informacao.aviso=4;
                        }
    
    
        
        }

  2. #2
    SAMARAS std10093's Avatar
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    Code:
     char verifica;
    this is a char ,not a string.
    Hope this helps

  3. #3
    ch4
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    verifica it's a character, not an array of characters.
    Try char verifica[200]; and check again arguments of strcmp.

  4. #4
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    I had already done that and the Warning is passing argument 1 of ‘strcmp’ makes pointer from integer without a cast

  5. #5
    SAMARAS std10093's Avatar
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    Can you post the updated try?

  6. #6
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    Here it is, this is a function, if you want I can post my main too.

    Code:
    void leitura(char linha[200], info informacao){
    
    
    	char verifica[200];
    
    
    	/*Usa-se if e [strcmp] para verificar sscanfs*/
    
    
    	sscanf(linha,"%s",&verifica);
    
    
    	if(strcmp(verifica[4],"DATA")==0){
    
    
    		sscanf(linha,"DATA %d %d %d\n",&informacao.dia,&informacao.mes,&informacao.ano);
    		informacao.aviso=1;
    	
    				}
    
    
    	if(strcmp(verifica[4],"AREA")==0){
    
    
    		sscanf(linha,"AREA %d %d %d %d\n",&informacao.x1,&informacao.y1,&informacao.x2,&informacao.y2);
    		informacao.aviso=2;
    				}
    
    
    	if(strcmp(verifica[9],"INDIVIDUO")==0){
    
    
    		sscanf(linha,"INDIVIDUO %d %d %d %d\n",&informacao.especie,&informacao.individuo,&informacao.x_individuo,&informacao.y_individuo);
    		informacao.aviso=3;
    					}
    
    
    	if(strcmp(verifica[7],"COLONIA")==0){
    
    
    		sscanf(linha,"COLONIA %d %d %d %d %d\n",&informacao.especie_col,&informacao.colonia,&informacao.tamanho,&informacao.x_colonia,&informacao.y_colonia);
    		informacao.aviso=4;
    					}
    
    
    	
    	}
    Thanks for the help!

  7. #7
    SAMARAS std10093's Avatar
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    This compiles??
    You have as argument char linha[200]
    When i need to pass something like that i use to write
    Code:
    void leitura(char* linha, int linhaSize, info informacao){..
    when i call the function i will pass 200 as 2nd parameter.Then inside the body of the function,you are able to treat linha as an array

  8. #8
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    then inside what do I do so the function knows 200 is linha's size?

  9. #9
    and the hat of wrongness Salem's Avatar
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    > sscanf(linha,"%s",&verifica);
    > if(strcmp(verifica[4],"DATA")==0)
    It's just

    sscanf(linha,"%s",verifica);
    if(strcmp(verifica,"DATA")==0)


    You don't say [4] because you're comparing 4 letters.
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  10. #10
    SAMARAS std10093's Avatar
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    This is for your convenience.If you do not need the size,do not pass it as a parameter

  11. #11
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    Oh,so I'm not obliged to pass the size of linha into my new function?
    Okay,

    Thanks a lot, I'll see if it works and I'll update here

  12. #12
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    Quote Originally Posted by std10093 View Post
    This compiles??
    You have as argument char linha[200]
    When i need to pass something like that i use to write
    Code:
    void leitura(char* linha, int linhaSize, info informacao){..
    when i call the function i will pass 200 as 2nd parameter.Then inside the body of the function,you are able to treat linha as an array
    Yeah, it compiles. Arrays decay to a pointer to the first element when passed to a function, so the compile ignores any number in the left-most set of array brackets. If there's only one set of brackets, it ignores the number in there. It's not wrong to put it, but it's pointless. The following are all equivalent:
    Code:
    void leitura(char linha[200])  // the 200 is ignored, which is like having empty brackets, and...
    void leitura(char linha[])     // the empty brackets decay to a pointer
    void leitura(char *linha)    // so it ends up equivalent to this
    Note, this is only true for the left-most set of brackets. If you have a multi-dimensional array, you must specify all the dimensions except the left-most.
    Quote Originally Posted by Chinchila View Post
    then inside what do I do so the function knows 200 is linha's size?
    You pass a second parameter, like linhaSize, as std10093 suggested. Wherever you call the function, you must pass the correct size of the array into that parameter.

  13. #13
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    Well, now strcmp is saying I'm making a pointer from an integer:

    Code:
    void leitura(char *linha, info informacao){
    
    
    	char verifica;
    
    
    	/*Usa-se if e [strcmp] para verificar sscanfs*/
    
    
    	sscanf(linha,"%s",&verifica);
    
    
    	if(strcmp(verifica,"DATA")==0){
    
    
    		sscanf(linha,"DATA %d %d %d\n",&informacao.dia,&informacao.mes,&informacao.ano);
    		informacao.aviso=1;
    	
    				}
    
    
    	if(strcmp(verifica,"AREA")==0){
    
    
    		sscanf(linha,"AREA %d %d %d %d\n",&informacao.x1,&informacao.y1,&informacao.x2,&informacao.y2);
    		informacao.aviso=2;
    				}
    
    
    	if(strcmp(verifica,"INDIVIDUO")==0){
    
    
    		sscanf(linha,"INDIVIDUO %d %d %d %d\n",&informacao.especie,&informacao.individuo,&informacao.x_individuo,&informacao.y_individuo);
    		informacao.aviso=3;
    					}
    
    
    	if(strcmp(verifica,"COLONIA")==0){
    
    
    		sscanf(linha,"COLONIA %d %d %d %d %d\n",&informacao.especie_col,&informacao.colonia,&informacao.tamanho,&informacao.x_colonia,&informacao.y_colonia);
    		informacao.aviso=4;
    					}
    
    
    	
    	}

  14. #14
    C++ Witch laserlight's Avatar
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    Because verifica, being a char, is an integer, but strcmp's first parameter is a pointer to char. The problem is that verifica should be an array, thus it will be converted to a pointer to char. Since it is only a char, your use of sscanf with the %s format specifier to read into it is wrong too.
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  15. #15
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    So, what should I do to make it right?
    The logic is, I take from fgets(linha) into verifica with a sscanf, and then I want it to be compared in strcmp.
    I'm in the dark. Thanks

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