Thread: errno

You are trying to strcat() onto a string constant. Even if it didn't cause a segfault, it would make no sense

I can't do:

strcat(descricao[errno]," - Cód.: ");
strcat(descricao[errno],itoa(errno));

That's because I'm trying to modify a literal (descricao), which is not possible.

Right??



Then, I've tried this, but not works too:

Code:

char *erro;

erro = descricao[errno];
strcat(erro," - Cód.: ");
strcat(erro,itoa(errno));
return erro;

Why?

ok brewbuck

I had not seen your post ... hehe



but why this not work?

Code:

char *erro;

erro = descricao[errno];
strcat(erro," - Cód.: ");
strcat(erro,itoa(errno));
return erro;

How can i do that? Can you post a example?

Originally Posted by galindro

Then, I've tried this, but not works too:

Code:

char *erro;

erro = descricao[errno];
strcat(erro," - Cód.: ");
strcat(erro,itoa(errno));
return erro;

Why?

The line "erro = descricao[errno]" just makes erro point at the same string constant. You need to actually strcpy(erro, descricao[errno]) -- the rest of the code is correct, provided you actually allocate some space for erro. Currently, it's just an uninitialized pointer.

This is the solution:

Code:

char *abrir_arquivo(char *arquivo)
{
    FILE *fp;
    char *erro;
    char *codstr    = " - Cod.: ";
    char *desconstr = "Erro desconhecido";
    char *abertostr = "Aberto";


    if ((fp = fopen(arquivo, "r")) == NULL) {
        if ((errno >= 0) && (errno <= 2)) {
            erro = malloc(strlen(descricao[errno]) + 
                          strlen(codstr) +
                          strlen(itoa(errno) + 1));
            strcpy(erro, (descricao[errno]));
            strcat(erro, codstr);
            strcat(erro, itoa(errno));
        }
        else {
            erro = malloc(strlen(desconstr)+1);
            strcpy(erro, desconstr);
        }
    }
    else {
        erro = malloc(strlen(abertostr) + 1);
        strcpy(erro, abertostr);
    }
    return erro;
}

int main(void)
{
    char *message;
    message = abrir_arquivo("asdasdasd");
    printf("%s\n", message);
    free(message);
    return EXIT_SUCCESS;
}

It works perfectly. Thanks for all.