Initializing array of structure!!

[Chandrashekar Tippur]

All,

I need to initialize an array of structures but I don't know how may
elements are there. I tried to malloc the array but I am not sure how
to initialize them.

Snippet:
struct myarray{
int conf;
char * var;
};

int main(int args, char * argv[]){
struct myarray *MYARRAY[]= malloc(sizeof(s truct myarray) *
30);
MYARRAY={{1,"x" }, {2,"y"} ...... }; // How do I initialize
this?
}

This comes out with segmentation fault. How do I do this?

- Shekar

[Neo]

Re: Initializing array of structure!!


"Chandrashe kar Tippur" <ctippur@msn.co m> wrote in message
news:629c1390.0 411182225.4e65c 0db@posting.goo gle.com...[color=blue]
> All,
>
> I need to initialize an array of structures but I don't know how may
> elements are there. I tried to malloc the array but I am not sure how
> to initialize them.
>
> Snippet:
> struct myarray{
> int conf;
> char * var;
> };
>
> int main(int args, char * argv[]){
> struct myarray *MYARRAY[]= malloc(sizeof(s truct myarray) *
> 30);
> MYARRAY={{1,"x" }, {2,"y"} ...... }; // How do I initialize
> this?
> }
>
> This comes out with segmentation fault. How do I do this?
>
> - Shekar[/color]

You can do it like this :

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

#define ELEMENT_COUNT 4

struct mystruct {
int i;
char *p;
};

int main()
{
int i;
struct mystruct *MYARRAY = NULL;
if(MYARRAY = malloc(sizeof(s truct mystruct) * ELEMENT_COUNT))
{
for(i=0; i < ELEMENT_COUNT; i++)
{
MYARRAY[i].i = i;
MYARRAY[i].p = NULL;
}
for(i=0; i < ELEMENT_COUNT; i++)
printf("%d : %p\t", MYARRAY[i].i, MYARRAY[i].p);

free(MYARRAY);
}
return 0;
}

-Neo

[Method Man]

Re: Initializing array of structure!!


"Chandrashe kar Tippur" <ctippur@msn.co m> wrote in message
news:629c1390.0 411182225.4e65c 0db@posting.goo gle.com...[color=blue]
> All,
>
> I need to initialize an array of structures but I don't know how may
> elements are there.[/color]

In your posted code, you seem to know the element count (30).
[color=blue]
> I tried to malloc the array but I am not sure how
> to initialize them.[/color]

You're initialization technique works, but you've incorrectly declared your
array. See below.
Also, make sure to include this:

#include<stdio. h>
[color=blue]
>
> Snippet:
> struct myarray{
> int conf;
> char * var;
> };
>
> int main(int args, char * argv[]){
> struct myarray *MYARRAY[]= malloc(sizeof(s truct myarray) *
> 30);[/color]

Change that to:
struct myarray *MYARRAY = malloc(sizeof(M YARRAY) * 30);

[snip]

[Method Man]

Re: Initializing array of structure!!


"Method Man" <a@b.c> wrote in message
news:PXind.1228 6$14.391@read1. cgocable.net...[color=blue]
>
> "Chandrashe kar Tippur" <ctippur@msn.co m> wrote in message
> news:629c1390.0 411182225.4e65c 0db@posting.goo gle.com...[color=green]
> > All,
> >
> > I need to initialize an array of structures but I don't know how may
> > elements are there.[/color]
>
> In your posted code, you seem to know the element count (30).
>[color=green]
> > I tried to malloc the array but I am not sure how
> > to initialize them.[/color]
>
> You're initialization technique works,[/color]

Oops, no it doesn't.

[Method Man]

Re: Initializing array of structure!!


"Method Man" <a@b.c> wrote in message
news:PXind.1228 6$14.391@read1. cgocable.net...[color=blue]
>
> "Chandrashe kar Tippur" <ctippur@msn.co m> wrote in message
> news:629c1390.0 411182225.4e65c 0db@posting.goo gle.com...[color=green]
> > All,
> >
> > I need to initialize an array of structures but I don't know how may
> > elements are there.[/color]
>
> In your posted code, you seem to know the element count (30).
>[color=green]
> > I tried to malloc the array but I am not sure how
> > to initialize them.[/color]
>
> You're initialization technique works,[/color]

Oops, no it doesn't.

[Peter Smithson]

Re: Initializing array of structure!!

In article <629c1390.04111 82225.4e65c0db@ posting.google. com>,
ctippur@msn.com says...[color=blue]
> All,
>
> I need to initialize an array of structures but I don't know how may
> elements are there. I tried to malloc the array but I am not sure how
> to initialize them.[/color]

How about -

struct myarray{
int conf;
char * var;
};

int main(int args, char * argv[])
{
struct myarray MYARRAY[]= {{1,"x"}, {2,"y"}};
/* Check that it worked - */
printf("%d %s\n", MYARRAY[0].conf, MYARRAY[0].var);
printf("%d %s\n", MYARRAY[1].conf, MYARRAY[1].var);
}


--

http://www.beluga.freeserve.co.uk

[Mark McIntyre]

Re: Initializing array of structure!!

On 18 Nov 2004 22:25:46 -0800, in comp.lang.c , ctippur@msn.com
(Chandrashekar Tippur) wrote:
[color=blue]
>All,
>
>I need to initialize an array of structures but I don't know how may
>elements are there. I tried to malloc the array but I am not sure how
>to initialize them.
>
>Snippet:
>struct myarray{
> int conf;
> char * var;
>};
>
>int main(int args, char * argv[]){
> struct myarray *MYARRAY[]= malloc(sizeof(s truct myarray) * 30);[/color]

MYARRAY is an array of pointers to struct myarray. You don't want that.
You want an array of structs.... so remove the square brackets.

Also, by convention ALL CAPS is reserved for macro names. Its bad practice
to use it for variables as it will confuse code maintainers later.

[color=blue]
> MYARRAY={{1,"x" }, {2,"y"} ...... }; // How do I initialize this?[/color]

If its dynamically created, you must dynamically assign values to it by
looping. Since you know how large it is, you could however have done

struct myarray TheArray[30] = {{1,"x"},{2,"y" }};
which would have populated the 1st to elements of the array, and set the
rest to zero or null.


--
Mark McIntyre
CLC FAQ <http://www.eskimo.com/~scs/C-faq/top.html>
CLC readme: <http://www.ungerhu.com/jxh/clc.welcome.txt >

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[Jack Klein]

Re: Initializing array of structure!!

On Fri, 19 Nov 2004 04:23:04 -0500, "Method Man" <a@b.c> wrote in
comp.lang.c:
[color=blue]
>
> "Chandrashe kar Tippur" <ctippur@msn.co m> wrote in message
> news:629c1390.0 411182225.4e65c 0db@posting.goo gle.com...[color=green]
> > All,
> >
> > I need to initialize an array of structures but I don't know how may
> > elements are there.[/color]
>
> In your posted code, you seem to know the element count (30).
>[color=green]
> > I tried to malloc the array but I am not sure how
> > to initialize them.[/color]
>
> You're initialization technique works, but you've incorrectly declared your
> array. See below.
> Also, make sure to include this:
>
> #include<stdio. h>[/color]
#include <stdlib.h>
[color=blue]
>[color=green]
> >
> > Snippet:
> > struct myarray{
> > int conf;
> > char * var;
> > };
> >
> > int main(int args, char * argv[]){
> > struct myarray *MYARRAY[]= malloc(sizeof(s truct myarray) *
> > 30);[/color]
>
> Change that to:
> struct myarray *MYARRAY = malloc(sizeof(M YARRAY) * 30);[/color]

No, no, NO!!!

struct myarray *MYARRAY = malloc(sizeof *MYARRAY * 30);

The OP wants an array of 30 structures, not 30 pointers to struct.

--
Jack Klein
Home: http://JK-Technology.Com
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