Random from dynamic memory allocation

[Gil Carvalho]

Hi

I have this code, can someone tell me if there is anything wrong with that??

void gp1_Ques(struct perg *p)
{
char * lista[200]; // mil perguntas com tamanho máximo de 255 caracteres
char *copia;
int count, random;
FILE *f;
if ((f = fopen("gp1.dat", "rb")) == NULL)
{
  printf("Erro ao abrir ficheiro\n");
}
else
{
  count = 0;
  while (fgets(lista[count], 200, f) == lista[count])
  {
copia=malloc(sizeof *lista[count]);
   count++;
  }
  // fechar ficheiro
  fclose(f);
  //escolher pergunta
  random=rand() % count;
}
for (i=0; i <count-1; i++)
{
printf("%s\n",lista[random]);
  free(copia);
}
}

Well new data

iv'e got this using debuger

Program received signal SIGSEGV, segmentation fault

copia = 0x4050a3"%d"
i = 1976527024
random = 1976527113
count = 0
f = 0x75d22960

with this line

while (fgets(lista[count], 200, f) == lista[count])

Any help?

[Salem]

I'm looking at your post count, and wondering why your code is still an eyesore to look at.

Look at this

int main ( ) {
    // do some stuff
    printf("tada!!!");
    return 0;
}

Look at your code


Now back to this

int main ( ) {
    // do some stuff
    printf("tada!!!");
    return 0;
}

Do you see
- fixed pitch fonts
- line numbers
- syntax colouring

[Gil Carvalho]

Let me try now.

void gp1_Ques(struct perg *p)
{
	char * lista[200]; // mil perguntas com tamanho máximo de 255 caracteres
	char *copia;
	int count, random, i;
	FILE *f;
	if ((f = fopen("gp1.dat", "rb")) == NULL)
	{
		printf("Erro ao abrir ficheiro\n");
	}
	else
	{
		count = 0;
		while (fgets(lista[count], 200, f) == lista[count])
		{
			copia=malloc(sizeof *lista[count]);
			count++;
		}
		// fechar ficheiro
		fclose(f);
		//escolher pergunta
		random=rand() % count;
	}
	for (i=0; i <count-1; i++)
	{
		printf("%s\n",lista[random]);
		free(copia);
	}
}

[iMalc]

Google translates the comment on line 3 as: "thousand questions with a maximum length of 255 characters". I have no idea where you think 255 comes from.

Your bugs are on lines: 14, 16, 24, and presumably line 26 isn't what you want either.

You have to allocate room to store some text, before you try and read it in. Allocating more than one character would help too.

[Gil Carvalho]

Hi,
Thanks

You have to allocate room to store some text, before you try and read it in
Excuse me but i don't know how to do it.

Can you tell me how please?

[Salem]

Well normally, you would read lines from a file like so

#define MAX_LINES 200
char * lista[MAX_LINES];
char buff[BUFSIZ]; // BUFSIZ is in stdio.h
int count = 0;
while ( count < MAX_LINES &&
        fgets(buff,BUFSIZ,f) != NULL ) {
    // trim the newline from buff - if you need to, see the FAQ
    // work out the length of buff
    // allocate that much space using malloc, store the pointer in lista[count]
    // copy from buff to your allocated memory
    // increment the count
}

[Gil Carvalho]

Hi

I used like this:

void gp1_Ques(struct perg *p)
{
  char * lista[100];  // 100 perguntas, o tamanho de cada não é especificado aqui
  int count, random, i;
  FILE *f;
  if ((f = fopen("gp1.dat", "rb")) == NULL)
  {
        printf("Erro ao abrir ficheiro\n");
  }
  else
  {  
        for (count = 0;; count++)
        {
          lista[count] = malloc(200);
          if (fgets(lista[count], 200, f) == NULL)
          {
                free(lista[count]);
                break;
          }
        }
        // fechar ficheiro
        fclose(f);
        // escolher pergunta
        random=rand() % count;
        printf("%s\n",lista[random]);
        for (i=0; i < count; i++)
        {
          free(lista[i]);
        }
  }

What do you think?

[Salem]

I think you need to limit count to the number of elements in your lista array.

[Gil Carvalho]

I think you need to limit count to the number of elements in your lista array.

Instead of 200 i must 100 like lista array has?

Thnaks

[Salem]

> Instead of 200 i must 100 like lista array has?
Your point being?

Did you not figure that you could change
#define MAX_LINES 200
into
#define MAX_LINES 100

[Gil Carvalho]

Already did it Salem

Thank you for your help.

Best regards

[Gil Carvalho]

Hi all

I thought this was ok since i had no errors but when i'm running the function nothing goes like i want.

void gp1_Ques(struct perg *p)
{
    #define MAX_LINES 250
    char * lista[MAX_LINES];
    char buff[BUFSIZ]; // BUFSIZ is in stdio.h
    int count = 0;
    int i, random;
    FILE *f;
    if ((f = fopen("gp1.dat", "rb")) == NULL)
    {
        printf("Erro ao abrir ficheiro\n");
    }
    else
    {
        for (count = 0;; count++)
        {
          lista[count] = malloc(250);
          if (fgets(lista[count], 250, f) == NULL)
          {
                free(lista[count]);
                break;
          }
        }
    }
        // fechar ficheiro
        fclose(f);
        // escolher pergunta
        random=rand() % count;
        printf("Count %d  and random %d",count, random);
        printf("%s\n",lista[random]);
        for (i=0; i < count; i++)
        {
          free(lista[i]);
        }
}

Well, the function works until
printf("Count %d and random %d",count, random);

Doesn't give me the list, and the numbers from count is 242 and random last time was 41.

The count is wrong since i have only 20 records, so i think that 242 is the characters from the file. (binary file)

My file is the following

O que se come no Sao Martinho?
ðµþÿ ÿÿÿÿ ݯM4• `@` t—„4• • €kH4• ÚqO4•
p´þÿ �
@ Nozes
þÿ 5…Castanhas
Natas
jƒ4• Chourico
Os rojoes tipicos são à moda do...
þÿ ÿÿÿÿ ݯM4• `@` t—„4• • €kH4• ÚqO4•
p´þÿ �
@ Porto
þÿ 5…Alentejo
Minho
jƒ4• Douro
o
Quem e o actual presidente do Patido Socialista (PS)?
ÿÿÿÿ ݯM4• `@` t—„4• • €kH4• ÚqO4•
p´þÿ �
@ Soares
ÿ 5…Socrates
Seguro
ƒ4• Cavaco

Qual a capital das Filipinas?
atido Socialista (PS)?
ÿÿÿÿ ݯM4• `@` t—„4• • €kH4• ÚqO4•
p´þÿ �
@ Manila
ÿ 5…Banguecoque
Seoul
ƒ4• Pequim

Qual a capital de Cuba?
nas?
atido Socialista (PS)?
ÿÿÿÿ ݯM4• `@` t—„4• • €kH4• ÚqO4•
p´þÿ �
@ Bayamo
ÿ 5…Santa Clara
Las Tunas
 Havana

Quem foi o realizador do filme "Gladiador"?
ta (PS)?
ÿÿÿÿ ݯM4• `@` t—„4• • €kH4• ÚqO4•
p´þÿ �
@ James Cameron
Peter Jackson
R.Zemeckis
ki Ridley Scott
Quantas Taças de Portugal já conquistou o S.L. Benfica?
ÿÿÿÿ ݯM4• `@` t—„4• • €kH4• ÚqO4•
p´þÿ �
@ 19
s Cameron
12
r Jackson
24
meckis
ki 26
ey Scott
Quem venceu o Campeonato do Mundo, disputado na Argentina, em 1978?
¯M4• `@` t—„4• • €kH4• ÚqO4•
p´þÿ �
@ Brasil
meron
Inglaterra
n
Argentina
ki Alemanha
tt
Em que ano foi fundada a NASA?
o, disputado na Argentina, em 1978?
¯M4• `@` t—„4• • €kH4• ÚqO4•
p´þÿ �
@ 1955

meron
1956
erra
n
1957
ina
ki 1958
ha
tt

Mozart era?
i fundada a NASA?
o, disputado na Argentina, em 1978?
¯M4• `@` t—„4• • €kH4• ÚqO4•
p´þÿ �
@ Hungaro
eron
Alemao
ra
n
Austriaco
ki Portugues
t
Que actriz foi galardoada com o Óscar de melhor actriz em 2000?
?
¯M4• `@` t—„4• • €kH4• ÚqO4•
p´þÿ �
@ Hillary Swank
Halle Barry

C. Theron
ron Julia Roberts
Cor predominante da Bandeira da �ustria?
elhor actriz em 2000?
?
¯M4• `@` t—„4• • €kH4• ÚqO4•
p´þÿ �
@ Laranja
wank
Vermelho
y

Azul
ron
ron Verde
oberts

Numero pertencente a sequaencia 2, 4, 8, 16, 18, 32, 64...
000?
?
¯M4• `@` t—„4• • €kH4• ÚqO4•
p´þÿ �
@ 254
ja
wank
2046
ho
y

132
ron
ron 4096
oberts
O mesmo que setentrional?
ncia 2, 4, 8, 16, 18, 32, 64...
000?
?
¯M4• `@` t—„4• • €kH4• ÚqO4•
p´þÿ �
@ Norte

wank
Sul
ho
y

Leste
on
ron Oeste
oberts
O numero 101 em romanos?
ncia 2, 4, 8, 16, 18, 32, 64...
000?
?
¯M4• `@` t—„4• • €kH4• ÚqO4•
p´þÿ �
@ CI
e

wank
MI
ho
y

DI
e
on
ron EI
e
oberts
O Aeroporto Internacional Orly situa-se em
18, 32, 64...
000?
?
¯M4• `@` t—„4• • €kH4• ÚqO4•
p´þÿ �
@ Alemanha
ank
Espanha
y

Franca
n
ron Italia
berts
Antes de embarcar num voo qualquer, qual é o procedimento que tem de seguir?
`@` t—„4• • €kH4• ÚqO4•
p´þÿ �
@ Check saude

Check dentes
Check out
ron Check in
rts
Qual destes paÃ..ses não pertence ao continente Europeu?
que tem de seguir?
`@` t—„4• • €kH4• ÚqO4•
p´þÿ �
@ Portugal
e

Marrocos
es
Espanha

ron Lituania
rts
Qual a serra mais alta de Portugal?
continente Europeu?
que tem de seguir?
`@` t—„4• • €kH4• ÚqO4•
p´þÿ �
@ Marao
l
e

Serra Estrela
Caldeirao
ron Arrabida
rts
Onde nasce o rio Tejo
de Portugal?
continente Europeu?
que tem de seguir?
`@` t—„4• • €kH4• ÚqO4•
p´þÿ �
@ Franca

e

Alemanha
ela
Portugal
ron Espanha
rts

Anyone knows whats wrong with this code??

Thanks

[gemera]

Judging by the size of your file the 242 would probably refer to the number of LINES, which is what your program is reading. The file, btw, as you have presented it, is corrupt anyway so may not be usable. Line 41 seems to coincide with a blank line which would give you seemingly nothing. In order for your program to work the way you want, you would need to think about reading and storing in a more sophisticated manner, perhaps reading and storing each record as a structure?

[Salem]

That file is totally unsuitable for reading using fgets

If this is a continuation of your previous question and answers thread, then you NEED to use the same structure and then use fread(), as you used to fwrite() the file to begin with.

Your char *lista[MAX] would need to be struct perg *lista[MAX]

[QuantumPete]

I thought this was ok since i had no errors but when i'm running the function nothing goes like i want.

Code compiling without errors (and warnings hopefully) is no guarantee that it does what you want! It just means you don't have any compiler errors (or warnings)