Thread: fgets, fputs, and malloc.

Hmm, I was trying to test the stdin and stdout you talked about and here's what I got:

Code:

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

int main(void)
{
	int x[8], i, j, *p;
	p = malloc(sizeof(int) * 8);
	printf("Enter at least 8 integers (press q when done)");
	while( getchar() != 'q')
	{
	for(i = 0; i < strlen(x); i++) fgets(x[i], 15, stdin);
	for(j = 0; j < strlen(x); j++) fputs(x[j], 15, stdout);
	}

	free(p);
	
	getchar();
	return 0;
}

There are a lot of errors:

Code:

untitled.c:12: warning: passing argument 1 of ‘strlen’ from incompatible pointer type
untitled.c:12: warning: passing argument 1 of ‘fgets’ makes pointer from integer without a cast
untitled.c:13: warning: passing argument 1 of ‘strlen’ from incompatible pointer type
untitled.c:13: warning: passing argument 1 of ‘fputs’ makes pointer from integer without a cast
untitled.c:13: warning: passing argument 2 of ‘fputs’ makes pointer from integer without a cast
untitled.c:13: error: too many arguments to function ‘fputs’

What am I doing wrong?

and btw,
for example,
if I do this:

Code:

int x[], *p;
p = malloc(sizeof(int)); // what do I put here? * what?

I mean, what is the malloc parameter if I don't know x's size?

No, no, no. Don't use fgets to read int non-char buffers.
It's used to read strings. If you don't need to read a string, you can use scanf, or fscanf.
int x[] isn't valid. You must specify a size.
As for your p - well, that's kinda up to you and what you want to use it for. Just make sure you have enough space allocated when messing around writing data to it.

And why do I see so many problems with that code?
Why do you need p in the first place? You're not using it anywhere. Secondly, you're allocating 8 INTs of memory for it while p is a CHAR pointer.
x contains 8 elements, and you're trying to read 15 bytes. Very bad. Buffer overrun right there.

Code:

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

int main(void)
{
	char x[8], *p;
	int i;
	
	p = malloc(sizeof(char) * 8);
	
	printf("Enter your name");
	fgets(x, 8, stdin);
	
	for(i = 0; i < strlen(x); i++)
		fputs(x[i], strlen(x), stdout);

	free(p);
	
	getchar();
	return 0;
}

I corrected anything you told me (well, except from the memory allocating which doesn't appear to be a problem) and it still doesn't work!

fputs writes a pointer to a stream, NOT a char. x[i] = char x = char* (pointer)
And p is still superfluous - it's not used by anything. You only allocate memory and release it - totally unnecessary,
Actually, enable warnings on your darn compiler, because char != char*. And writing 8 bytes from a single char? Oh, the horror!

perhaps he should be usuing fputc()

ssharish

Originally Posted by eXeCuTeR

why fputs(x, stdout);?
it gets 3 parameters and not 2, how is this possible?

Because fputs doesn't need to read into a buffer and therefore does not need to know the buffer length. It reads the string and writes all the characters in the string until it encounters the NUL char.

Originally Posted by eXeCuTeR

and why is my memory allocating is bad?
I mean, what if the user's name is Chris so not all the memory is used, only 5 byte of it and not 8.

Because you're not using it for anything. All you're using the local variable!

Originally Posted by eXeCuTeR

and why fgets(x, sizeof(x), stdin) - fgets(x, 8, stdin) is good either, isn't it?

and how do I make a warning is the input isn't a character?

Err, what is supposed to do?
For warnings, check compiler settings. You could tell what compiler you're using so someone can help.

Originally Posted by ssharish2005

perhaps he should be usuing fputc()

ssharish

What's the point since obviously the entire string is written?