errno

How can i get the number of errno to pass to a function?

errno is a global variable that is always available to your program. Just use it like you would an int that you defined yourself.

And, since it's global, your function already has access to it.

Todd

#include <errno.h>

I know they are global variable, but i need to control an array with the value passed by errno. But, they not works. Here is the code:

Code:

---

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>

const char *descricao[] = {"Operação não permitida", "Arquivo ou diretório inexistente"};

const char *abrir_arquivo(char *arquivo)
{
        FILE *fp;
        if ((fp = fopen(arquivo, "r")) == NULL)
                return descricao[errno];
        else
                return "Ok";
}

int main (void)
{
        printf("%s\n", abrir_arquivo("asdasdasd"));
        return 1;
}

---

This code returns this following error message:
Segmentation fault (core dumped)

Its probably the errno is greater than 1, then the error is displayed.

This follows worked perfectly, but has much work (I need to do this in 92 messages) and the code is not professional:

Code:

---

char *erro(int erro)
{

        switch(erro)
        {
                case 1:
                        return "Operação não permitida";
                        break;
                case 2:
                        return "Arquivo ou diretório inexistente";
                        break;
        }
       
}

const char *abrir_arquivo(char *arquivo)
{
        FILE *fp;
        if ((fp = fopen(arquivo, "r")) == NULL)
                return erro(errno);
        else
                return "Ok";
}

int main (void)
{
        printf("%s\n", abrir_arquivo("asdasdasd"));
        return 1;
}

---

My question is:
How can I pass the correct number of errno to my function, so that this error is not more show?

Eh? Why not just call strerror()? The whole purpose of strerror() is to convert errno values to strings. It uses the locale, so it should display in the correct language. As a bonus, your error messages will work in other languages as well.

Or just perror?

Quote:

---

Originally Posted by Dave_Sinkula

Or just perror?

---

Sure, if all you're going to do is display the message anyway, just call perror().

I do not want to call strerror nor perror because I must translate the error messages to Portuguese.

Do you know any way to translate them?

Thanks for the help.

How can I access the locale to translate then?

Thanks and sorry for my bad reply...

Sounds like a couple hours of work for someone who knows English and Portuguese.

I know english and portuguese. Im from Brazil.

Quote:

---

Originally Posted by galindro

How can I access the locale to translate then?

Thanks and sorry for my bad reply...

---

The locale is supposed to be set automatically. If you are running a Portuguese version of Windows, then perror() should automatically show error messages in Portuguese. If you're running some form of UNIX, then you just need to make sure your locale is configured properly. How you do it is OS-dependent.

Point begin, you don't have to do anything in the code to make it happen.

Quote:

---

Originally Posted by galindro

My question is:
How can I pass the correct number of errno to my function, so that this error is not more show?

---

Your code is correct, except that judging from your working code:

Code:

---

char *erro(int erro)
{

        switch(erro)
        {
                case 1:
                        return "Operação não permitida";
                        break;
                case 2:
                        return "Arquivo ou diretório inexistente";
                        break;
        }
       
}

---

Your array probably should be:

Code:

---

const char *descricao[] = {"OK", "Operação não permitida", "Arquivo ou diretório inexistente"};

---

Your previous code would attempt to use the third element of an array with 2 elements - which damn well should segfault.

Also, in Linux/Unix, most likely setting the environment variable C_LOCALE to something sensible. More info by doing "man locale" and listing the locale names by "locale -a".

--
Mats

matsp, thank you for the help.

The errno messages of FreeBSD, returns number between 1 and 92. The index of arrays in C, begins with 0. Here is the error. The errno returns me the number 2, but the max value of my array is 1!!!

Here is the correct code:

Code:

---

const char *descricao[] = {"", "Operação não permitida", "Arquivo ou diretório inexistente"};

const char *abrir_arquivo(char *arquivo)
{
        FILE *fp;
        int *a;
       
        if ((fp = fopen(arquivo, "r")) == NULL)
        {
                if ((errno >= 0) && (errno <= 2))
                        return descricao[errno];
                else
                        return "Erro desconhecido";
        }               
        else
                return "Aberto";
}

int main (void)
{
        printf("%s\n", abrir_arquivo("asdasdasd"));
        return 1;
}

---

Thanks for all

Best Regards!

:D

Now, I've got the same error, when I try to concat strings:

Segmentation fault (core dumped)

Here is the code:

Code:

---

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>

#define INTSIZE 2

char *itoa(int value)
{
        int count, i, sign;
        char *ptr, *string, *temp;

        count = 0;
        if ((sign = value) < 0)
        {                                               
                value = -value;               
                count++;                       
        }


        temp = (char *) malloc(INTSIZE + 2);
        if (temp == NULL)
        {
                return(NULL);
        }
        memset(temp,'\0', INTSIZE + 2);

        string = (char *) malloc(INTSIZE + 2);
        if (string == NULL)
        {
                return(NULL);
        }
        memset(string,'\0', INTSIZE + 2);
        ptr = string;


        do
        {
                *temp++ = value % 10 + '0';
                count++;
        } while (( value /= 10) >0);

        if (sign < 0)
                *temp++ = '-';

        *temp-- = '\0';

        for (i = 0; i < count; i++, temp--, ptr++)
        {
                memcpy(ptr,temp,sizeof(char));
        }

        return(string);
}

char *descricao[] = {"", "Operação não permitida", "Arquivo ou diretório inexistente"};

char *abrir_arquivo(char *arquivo)
{
        FILE *fp;
        char *erro;

 
        if ((fp = fopen(arquivo, "r")) == NULL)
        {
                if ((errno >= 0) && (errno <= 2))
                {
                        strcat(descricao[errno]," - Cód.: ");
                        strcat(descricao[errno],itoa(errno));
                        return descricao[errno];
                }       
                else
                        return "Erro desconhecido";
        }               
        else
                return "Aberto";
}

int main (void)
{
        printf("%s\n", abrir_arquivo("asdasdasd"));
        return 1;
}

---

Does anyone know what might be happening?

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