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;

---

Because you are trying to extend a string constant, and those are generaly read-only, not to mention that there's unlikely to be "space after" your string. Pass in a string that can be filled in, or have a static local string, or something like that.

--
Mats

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

Quote:

---

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.

Quote:

---

Originally Posted by brewbuck

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.

---

And of course, erro in this case needs to be some valid memory, and if you are going to return it, better not make it a automatic local variable - either allocate memory, make it static or pass in a string to store it.

--
Mats

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.

:D

Code:

---

strlen(itoa(errno) + 1)

---

I doubt this retuns what you expect...
itoa is not standard
and better check the return value of malloc before using the buffer