[Dev-C++] Malloc Problem

[Iuri K. <IK...@am...>]

Dear Luigi,
	Thank you for your help. I tried to use calloc because de string
read from the
file string has diferent sizes. I.e. the first line of the file script =
is
"iuri", when I write:
fgets (linha1_ptr ,sizeof(linha1_ptr), script);
	It returns: iur
If I write:
fgets (linha1_ptr , 30 , script);
	It returns: iuri

With static memory the problem is that it reads the hole thing:
So if my string is:
	aaaaaaaaaa
	bbbb
With the fgets it will read:
	aaaaaaaaaa
	bbbb\0aaaa

I think with sizeof it shouldn't happen, but it does. He reads the size =
of
the 1=BA line and
returns this same size for every line, even if it's bigger.

				Thanks,
						Iuri

Date: Tue, 17 Jul 2001 19:46:44 +0200
To: dev...@li...
From: Luigi Santillo <gi...@li...>
Subject: Re: [Dev-C++] Malloc Problem
Reply-To: dev...@li...

In a C program you can ask for memory in a "static fashion" (i.e. at=20
compile time) and in a "dynamic fashion" (i.e. at execution time).

When you define "linha1" by the line:

char linha1[31];  /* 1 is for the terminating '\0' */

you are using static memory, this means that linha1 will be made of 30=20
chars during the whole execution, and its size is known at compile =
time.

If you wish to use dynamic memory, then I suggest you use calloc =
instead of=20
malloc (calloc is for arrays)

char *linha1;
...
linha1 =3D (char *)calloc(31, sizeof(char)); /* 1 is for the =
terminating '\0'
*/

When you no longer need the dynamically allocated variable linha1, you=20
should release the memory by the following:

free(linha1);

Dynamic memory is used when the size of the string is not known in =
advance,=20
since in your code, you already know that no string has more than 30 =
chars,=20
you should use static memory.

In my opinion your code should be:
---
#define MAX_SIZE 31
char linha1[MAX_SIZE];
...
fgets(linha1, MAX_SIZE, script);
...
---

At 12.51 17/07/01 -0300, you wrote:

>I can't find any tutorial about Malloc for strings.
>I want to read a string (line) from a file named 'script'. Each line =
has=20
>one string with diferent size.
>The MAX string will have 30 chars.
>I know it is very simple, but I can't find the solution.
>         Thanks,
>                         Iuri
>---------
>   char linha1 [30];
>   char *linha1_ptr =3D linha1;
>   linha1_ptr =3D malloc (30);
>...
>              fgets (linha1_ptr , sizeof(linha1_ptr) , script);
>              printf(linha1_ptr,"\n");
>              fputs(linha1_ptr, tudo);
>              write(sockfd, linha1_ptr, sizeof(linha1_ptr));
>              write(sockfd, "\n\r",2);
>------------

---
gisan




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