error conversion from array to int in c language

Question

Could someone help me understand what error I am making in this conversion. because any digit to print the last characters of the variable key_temp, key_temp2 or key, he is printing ' 0'.

// copies the data from argv1 to the key variable strcpy(key_temp2, argv[1]); // copies the string argv[1] to the key char_temp

for(int i = 0; i < compr_argv1; i++)            // tive que copiar a chave_temp2 para a chave_temp, porque estava gerando falha
{
    chave_temp[i] = chave_temp2[i];
    chave[i] = chave_temp[i];
}