Thread: Array of structs

is this possible ??

Code:

struct s{
char *name;
}MyArray[5];

is this will create array of structs or i am wrong because after compiling it i get the same answer ..

exampl when i put to the first element "first_name"
and the second element "second_name"
and if i output the first elemenet .. it will contain "second_name"..

this is More advance exmaple :

Code:

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

#define MAX2 100

struct s 
{
	char* id;              //array of structures Maximum of Five students,
};

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

	struct s MyArray[5];
	FILE *fp;

	char *r = NULL;
	char d[2];

	int n,j,k,m,l;
	int i=0;// counters
	int u=0;
                 
	
	char line[MAX2];


	if ((fp = fopen(argv[1],"r")) == NULL){
	    printf("cannot open the file that you specified\nThe file has to be in the same directory\n");
	    exit(1);}   
                d[0] = ':';
                d[1] = '\0';              
	
	i = 0;
	while((fgets(line,100,fp)) != NULL  )
	{
		n=0;
		for(k = 0; k < 100; k++){
			if (line[k] == '\n'){
				line[k] = '\0';
				break;
			}

		}

		r = strtok(line,d);
		MyArray[i].id = r;
		n = strlen(r);
		MyArray[i].id[n] = '\0';

		++i;
		
	}

	printf("%s\n",MyArray[0].id);
	
	fclose(fp);
	return 0;
}

the file-input

Code:

s1:csc212,csc281,csc361
s2:csc361,csc336,csc329
s3:csc336,csc327,csc212,csc281
s4:csc342,csc327,csc311,csc305
s5:csc212,csc281,csc327,csc380

output of the program:

Code:

s5

why every element in the array print s5 , i think it should print s1 ???

Well you have a pointer, so everything ends up pointing at the same thing.

So have something like
char id[20];

And
strcpy( MyArray[i].id, r );


> n = strlen(r);
> MyArray[i].id[n] = '\0';
These two lines are a waste of time. strtok() writes a \0, and strlen() returns the index position of the \0 (otherwise known as the length).
So all you're doing is overwriting one \0 with another \0.


> for(k = 0; k < 100; k++)
See the FAQ, there are easier ways of removing the \n.

thanks Salem , and is there a way to do it dynamicly ??

Code:

struct s* MyArray = malloc(num*sizeof(struct s))

Will give you num stucts.

ummm...no. id is a char*, so if you wanted to do that, you'd want to allocate chars instead of struct s's.

and if i have a struct that contain multiple id`s .. like this :

Code:

struct s{
char *id[4] ;
}MyArray[5];

can i do what salem say`s .. or it will be a problem

i mean is this true :

Code:

MyArray[i].d[j] = malloc(sizeof(char*));
strcpy(MyArray[i].id[j],r);

so what is the solution to this problem !!

thanks guys , finally i got every things works Ok .. "thanks word" is not enough to thank you..

and i appreciate your help all of you .

sorry my english is bad ,

> MyArray[i].d[j] = malloc(sizeof(char*));
> strcpy(MyArray[i].id[j],r);
It should be

Code:

if ( (MyArray[i].d[j] = malloc( strlen(r) + 1 )) != NULL ) {
    strcpy(MyArray[i].id[j],r);
} else {
    // out of memory
}