How to assign a string to a structure variable in C?

daYz · 06-11-2007, 12:38 PM

Hi,

I want to assign a string to a structure variable in C, but I'm not sure how to do that. Can someone show me how it can be done please?

The way I am trying to achieve it is:

Code:

#include <stdio.h>


main()
{

struct name{
     char array[8];
} variable;


//That goes well, but I'm not sure what to do next. I have tried a few things including this:


variable.array[8] = "string";


//But nothing works


return 0;

}

Thanks for your help.

Regards,

Ben

nc3b · 06-11-2007, 01:08 PM

O course it doesn't.

I am no OO programmer (in fact I'm hardly a programmer

) but here is something that works.

PHP Code:



#include <stdio.h> 
#include <cstdlib> 
#include <string.h> 
 
struct name 
{ 
    char *array; 
}variable; 
 
int assign(name *,const char *); 
 
int main() 
{ 
    char bla[]="The rain in Spain\n"; 
    assign(&variable,bla); 
    fputs(variable.array,stdout); 
} 
 
int assign(name *variable, const char *str) 
{ 
    if(variable) 
    { 
        variable->array=(char*)calloc(strlen(str),sizeof(char)); 
        strncpy(variable->array,str,strlen(str)); 
 
    } 
    return 0; 
}

Cheers.

daYz · 06-11-2007, 01:39 PM

Thanks for your help. Unfortunately I still don't understand it well. Can you tell me why it does not work the way I do it?

Can you provide some c code pherhaps, if it won't take too much effort.

Thanks.

Regards,

Ben

nc3b · 06-11-2007, 02:09 PM

That is actually C code. I enclosed it in php tags because it has syntax highlighting

.

You can't assign anything to an array, because it is a constant. That is right, some say that arrays and pointers are the same, only that arrays are constant pointers. I don't entirely agree with that, but, to some extent it is true. And more, one might have expected you to write variable.array = "string"; , it's a mistake I've also made.

In the sloppy code I posted, I create a struct and a pointer. Then, via calloc, I assign some memory and copy (strncpy) the char array to the array in the structure.

My guess is, after your questions, that in fact you are looking for C++ code. Check out <string> . I believe you'll like it.

rstewart · 06-11-2007, 02:20 PM

Hello,

In straight vanilla "C" you would "strncpy(variable.array, "string", sizeof(variable.array));", or "strcpy(variable.array, "string");"

You are not allowed to perform a byte assignment using an array such as you were trying in your samples. You must copy the string into the destination byte array one byte at a time. That is what the strcpy, strncpy, memcpy, etc functions perform for you.

I would suggest that you take a look at the man pages for the strcpy, strncpy, memcpy, etc functions to get a better understanding into what they offer, and how to use them.

Cheers!

daYz · 06-11-2007, 02:35 PM

Quote:

That is actually C code. I enclosed it in php tags because it has syntax highlighting .

Lol.

Hey thanks guys, it is clear to me now. I'm going to try to write some code myself tommorow.

Regards,

Ben

theNbomr · 06-13-2007, 09:24 AM

This should work.

Code:

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

struct name {
    char array[8];
};

int main( int argc, char * argv[] ){

struct name variable = {
 .array = "string"
};

	printf( "%s\n", variable.array );
        strcpy( variable.array, "char's" );
	printf( "%s\n", variable.array );

	exit(0);
}

The structure declaration is moved outside of any function/block. The structure definition can/should be inside any block. Initialization of the structure, per C99, is demonstrated. Assignment to the character array is demonstrated.

--- rod.

daYz · 06-13-2007, 02:38 PM

That works indeed.

Thanks theNbomr.

tlha_bshir · 07-06-2022, 06:15 AM

Hello Dear, You are trying to assign value directly to a string which is no valid way in c language programming you should also go through of my idea.

First try to include library of #include<string.h> at the top of your program.
This library contains many usefull functions like strcpy(copy string 2 to string 1),strcmp(two strings compare).
Lets see how is this done.

#include<string.h>

int main()
{
char fullname[20];
printf("--------------\n");
strcpy(fullname, "Talha Bashir");
printf("Your name : %s", fullname);
}

here it is...
do have a try dear

Keith Hedger · 07-06-2022, 07:34 AM

when assigning to a fixed length array like this it would probably be better to use strncpy as you can set the max number of bytes copied, strcpy could easily cause an overflow.

Code:

man strncpy

astrogeek · 07-06-2022, 11:07 AM

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