C-如何将扩展的char序列与函数strcmp（）比较？

Question

I need to compare whether string is equals or not to the following extended char sequence: "———" ( ALT + 0151 code repeated three times) that is in text file. How to do it with function strcmp() ?

A piece of the example text file (TSV):

Piracicaba Av. Armando Salles de Oliveira Lado par 13400-005 Centro Piracicaba Tv. Agostinho Frasson ——— 13400-008 Centro Piracicaba Av. Armando Salles de Oliveira Lado ímpar 13400-010 Centro

When I read the file and print the field is displayed "ùùù" on monitor.

The structure:

typedef struct {
    char cidade[50];
    char tipoLogradouro[20];
    char logradouro[50];
    char trecho[30];
    char cep[10];
    char bairro[50];
} Endereco;

The test is inside 'switch case' and the program is crashing in this part:

case 3:
      {
          if(strcmp(token, "———") == 0) // Change to "ùùù" and fails too. 
              strcpy(registro[i].trecho, NULL);
          else
              strcpy(registro[i].trecho, token);
          break;
      }

Thanks a lot.

Answer 1

Often in C, you can only use 7-bit ASCII in a quoted string, so for upper ASCII you need to use the \\x escape sequence with the hexadecimal code of the character. So, in your case you can type: "\\x97\\x97\\x97", since 97 is hex for 151 decimal.

case 3:
{
      if(strcmp(token, "\x97\x97\x97") == 0) 
          strcpy(registro[i].trecho, NULL);
      else
          strcpy(registro[i].trecho, token);
      break;
}

Answer 2

strcmp only fails on null, you can pretty much just do

if (strcmp(inputString,"———")==0){
   printf("Strings Equal\n")
} else{
   printf("Strings unequal")
}

If you're trying to just see if the string is in the larger string, strstr is the function your looking for not strcmp.

Answer 3

strcpy is for one thing and one thing only , and that is copying one string to another. If you give it NULL , that's not a string, and dereferencing a NULL pointer is going to cause a crash.

What you want is this:

 if (strcmp(token, "———") == 0)
    // Assign NULL pointer
    registro[i].trecho = NULL;
 else
    // Copy string to buffer
    strcpy(registro[i].trecho, token);

Remember strcpy is a very risky function to use as it assumes a lot of things about the destination buffer. If trecho isn't large enough to hold the token string, including NULL terminator , you get undefined behaviour. If token isn't properly NULL terminated you get undefined behaviour. There's a lot of ways this seemingly harmless code can go haywire.