How do I compare two strings in c

Question

Basically what I want to do. It is receiving a String at the command line.Only the String entered, have to be in the binary base, so I do an if to check whether it is binary or not. My problem is in if , because regardless of the value you enter. Always enter if. - Thank you for your help!

int main(){

     char binario [50][100]={"0000","0001","0010","0011","0100","0101","0110","0111","1000","1001","1010","1011","1100","1101","1110","1111"};

     char nome [50][100];

     int contador=0;

      printf("Insira um valor");
      scanf("%s",nome[0]);

    while(nome[contador]!='\0'){



            if (nome[0] != binario[contador])
            {
                printf("Base inicial invalida");
                break;
            }

            contador++;
     } 

     return 0;

}

Answer 1

Note this expression:

if (nome[0] != binario[contador])

The result of this will be the comparison between the address of two memory pointers. These two addresses will never be the same, and therefore, he will always enter the if.

What you will want is to use the function strcmp:

if (strcmp(nome[0], binario[contador]) != 0)

In the meantime, I would like to point out that your programme has other problems which raise the following doubts:

• Why declare 50 names if you only need 1?

• Why convert from decimal to binary using strings, tabulated values and trial-and-error instead of calculating successive divisions for this?

Answer 2

You can use the function strcmp, declared in header file (or file header) string.h. Note that the function strcmp compares the content of strings and not your size.

Example:

strcmp(string1,string2);

The function will return you up to three values. They are:

• = 0: both strings are identical.
• > 0: the first different character has a higher value than the other string.
• < 0: the first different character has a lower value than the other string.

See the example:

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

int main ()
{
  char key[] = "maçã";
  char buffer[80];
  do {
     printf ("Adivinhe minha fruta favorita? ");
     fflush (stdout);
     scanf ("%79s",buffer);
  } while (strcmp (key,buffer) != 0);
  puts ("Resposta correta!");
  return 0;
}

Exit:

Adivinhe minha fruta favorita? laranja
Adivinhe minha fruta favorita? maçã
Resposta correta!

Read here and here too _{in English}.