how to find available memory in linux box

I have a problem that is used to test memory leak as follows, however,
after each run of the program, if I am using the command "free" on the
linux box, I did not see any difference about the usable memory. My
questions are:
1) How to find out exact free memory that my program can use?
2) Use which command to do this (top, or free)
3) why it does not show memory leak in my case (I am using the linux
command free)

----------------------------------------------------------------------------------------------------------------
#include <iostream>
#include <new>
#include <stdlib.h>
using namespace std;


int main(){
int *p= new int[100000000];
if ( p == NULL ) cout << "Failed to allocate memory" << endl;
else {
p[0] = 1;
p[1] = 2;
p[2] = 3;
cout << "p[0] = " << p[0] << ", p[1] = " << p[1] << ", p[2]
= " << p[2] << endl;
}
}

--------------------------------------------------------------------------------------------------------------------------------------------

$ a.out
p[0] = 1, p[1] = 2, p[2] = 3
$ free
total used free shared buffers
cached
Mem: 3907304 3884812 22492 0 281760
3123052
-/+ buffers/cache: 480000 3427304
Swap: 4145288 16084 4129204
$ a.out
p[0] = 1, p[1] = 2, p[2] = 3
$ free
total used free shared buffers
cached
Mem: 3907304 3884812 22492 0 281760
3123052
-/+ buffers/cache: 480000 3427304
Swap: 4145288 16084 4129204

david wolf wrote:All good questions. Wrong newsgroup, though. Try 'comp.os.linux.*'
hierarchy. Good luck!

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

On Dec 7, 5:46 am, "david wolf" <yih...@gmail.comwrote:As your program 'a.out' finished the memory have been 'free', the
memory record is same. Some os implements copy-on-wirte tech, so the
virtual address (not memory) you alloc may not exist in physical
memory, until you write something to it. Try check /proc file system
instead of 'free' command. At last, It's not a good idear to check
memory leak like this, which program's (process's) memory leak you want
see ?

Thanks Xeranic.

But how to check /proc file system?

Xeranic wrote:

david wolf wrote:Because when your program terminates the OS reclaims the resources it
reserved.

Hi David,It depends on: you limits (ulimit -a) , available memory, etc
Use valgrind for this.

Best regards,
Volodymyr!

david wolf <yihucd@gmail.comwrote:This doesn't answer your question, but in case allocation fails, new
will throw an exception. If you want it to return NULL, you have to use
new(std::nothrow) or something like that.

--
Marcus Kwok
Replace 'invalid' with 'net' to reply

Yes, Valgrind is best.

On Dec 8, 1:43 am, "david wolf" <yih...@gmail.comwrote: