How can one return a 2D array from a function to the main?

[23354666]

I have this simple program where I am trying to return a pointer to an array of chars, the output comes something like:
0 : lllkkknnn
1 : kkknnn
2 : nnn

where the first element in the array aa[][] takes all the variables of the other elements in the same array.

I want the output to be something like:
0 : lllkkknnn
1 : kkknnn
2 : nnn

Appreciate your help.

Code
=============== =============== =======


char* negotiateKeysMa ster();

int main()
{
char* aa;
int i;
aa = negotiateKeysMa ster());

printf("0 : %s \n",aa[0]);
printf("1 : %s \n",aa[1]);
printf("2 : %s \n",aa[2]);


return 0;
}

char* negotiateKeysMa ster()
{
char keysChar[3][3];

strcpy(keysChar[0],"lll");
strcpy(keysChar[1],"kkk");
strcpy(keysChar[2],"nnn");

return &keysChar;
}

[23354666]

Sorry I want the output to be something like:
0 : lll
1 : kkk
2 : nnn
=============== =============== ============

I have this simple program where I am trying to return a pointer to an array of chars, the output comes something like:
0 : lllkkknnn
1 : kkknnn
2 : nnn

where the first element in the array aa[][] takes all the variables of the other elements in the same array.

I want the output to be something like:
0 : lllkkknnn
1 : kkknnn
2 : nnn

Appreciate your help.

Code
=============== =============== =======


char* negotiateKeysMa ster();

int main()
{
char* aa;
int i;
aa = negotiateKeysMa ster());

printf("0 : %s \n",aa[0]);
printf("1 : %s \n",aa[1]);
printf("2 : %s \n",aa[2]);


return 0;
}

char* negotiateKeysMa ster()
{
char keysChar[3][3];

strcpy(keysChar[0],"lll");
strcpy(keysChar[1],"kkk");
strcpy(keysChar[2],"nnn");

return &keysChar;
}

[gpraghuram]

Hi,
There are certain issues in your code
1)First u cant retun address of a local variable
2)u can get a char* to hold a char**

Try this code

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

char** negotiateKeysMaster();

int main()
{
char** aa=NULL;
int i;
aa = negotiateKeysMaster();
printf("0 : %s \n",aa[0]);
printf("1 : %s \n",aa[1]);
printf("2 : %s \n",aa[2]);


return 0;
}

char** negotiateKeysMaster()
{
	int lnVar=0;
	char **keysChar=(char**)malloc(sizeof(char*)*3);
	for(lnVar=0;lnVar<3;lnVar++)
	{
		keysChar[lnVar]=(char*)malloc(10);
	}
	strcpy(keysChar[0],"lll");
	strcpy(keysChar[1],"kkk");
	strcpy(keysChar[2],"nnn");
	return keysChar; 
}

[23354666]

It totally works, thank you.

do you recommend anything to read about pointers? something handy and easy to understand?

Regards,

Hi,
There are certain issues in your code
1)First u cant retun address of a local variable
2)u can get a char* to hold a char**

Try this code

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

char** negotiateKeysMaster();

int main()
{
char** aa=NULL;
int i;
aa = negotiateKeysMaster();
printf("0 : %s \n",aa[0]);
printf("1 : %s \n",aa[1]);
printf("2 : %s \n",aa[2]);


return 0;
}

char** negotiateKeysMaster()
{
	int lnVar=0;
	char **keysChar=(char**)malloc(sizeof(char*)*3);
	for(lnVar=0;lnVar<3;lnVar++)
	{
		keysChar[lnVar]=(char*)malloc(10);
	}
	strcpy(keysChar[0],"lll");
	strcpy(keysChar[1],"kkk");
	strcpy(keysChar[2],"nnn");
	return keysChar; 
}

[gpraghuram]

Hi,
I read C by Kerningham and Ritchie.
If u need u also can read it.

Thanks
Raghuram

[JosAH]

Hi,
I read C by Kerningham and Ritchie.
If u need u also can read it.

Thanks
Raghuram

K&R2 is the bible when it comes to C. When you've read it (and understood it)
cover to cover you've done it all. I don't recommend the ANSI/ISO report for starters.

kind regards,

Jos

[horace1]

It totally works, thank you.

do you recommend anything to read about pointers? something handy and easy to understand?

Regards,

as indicated by gpraghuram using malloc() is the obvious solution.
You could return a pointer to a static local variable, e.g.

typedef char charArray[3][10];

charArray* negotiateKeysMaster();

int main()
{
charArray* aa;
int i;
aa = negotiateKeysMaster();
printf("0 : %s \n",(*aa)[0]);
printf("1 : %s \n",(*aa)[1]);
printf("2 : %s \n",(*aa)[2]);

system("pause");
return 0;
}

charArray* negotiateKeysMaster()
{
static charArray keysChar;

strcpy(keysChar[0],"lll");
strcpy(keysChar[1],"kkk");
strcpy(keysChar[2],"nnn");
return &keysChar;
}

[weaknessforcats]

However, using a static variable causes the array to continue to exist for the life of the program. You are better off creating the array on the heap and returning the address you get from the "new" operator:

charArray* arr = new charArray;

return arr;

Then in main() you can:

delete arr;

when you are finished with it.

The "static" keyword is a deprecated feature in C++.

If you are writing in C, then use malloc() and free() insrtead of "new" and "delete".