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values to Structure

Posted on 2009-07-15
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Last Modified: 2012-05-07
Hi,

how can i pass values to a structure at runtime....from a file"A" with two lines in it. Using C.

lets suppose..........my senario:-
FILE  "A"--
name=webserver
serverIP=1.1.1.1;
---------------------
typedef struct
{ char *name;
 char * serverIPaddress;
}Server1;
typedef Server1 myServer;
i have to construct "myServer" structure using values from file.

using fgets i am getting the values and had even split them..but when i am trying to assign the value(S) to structure.....some thing is going wrong...both items in structure point to same memory..according my code. there fore is overwritten always.

how to avoid this.??



lets suppose  

while(fgets(filestr,50,FileSource)!=NULL) {

				OK = FillServerInfo(filestr); //where filestr is char*

			}

loop 1:

FillServerInfo(char *str)   //lets suppose str contains string "name=server" in it

  {

   char *strtemp

  // i split the value in str and only send the data through strtemp

    strtemp = strtok(filestr,"=");

   a = getnum(strtemp);  // returns the numeric value of strtemp. name=1,serverIp=2;

   strtemp = strtok(NULL,"=");
 

 switch(a)

 {

  case 1:

      myServer->name = strtemp;

      return 1;

  case 2:

   myServerIp->ServerIpaddress=strtemp;

  return  1;

}
 

will get correct value in myServer->name......but in next loop it is updated to serverIpaddress values.

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Question by:kishan66
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Accepted Solution

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Infinity08 earned 500 total points
ID: 24863139
The problem is that you use the same filestr buffer to read each line, and then the strtemp returned by strtok will always point within that buffer, even if the buffer changes.

What you have to do, is change this :

>>       myServer->name = strtemp;

to something like :

        myServer->name = (char*) malloc(strlen(strtemp) + 1);
        strcpy(myServer->name, strtemp);

in order to copy the data, rather than copy the pointer.
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Expert Comment

by:Infinity08
ID: 24863142
>> What you have to do, is change this :

Same for the ip of course.
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Expert Comment

by:flob9
ID: 24863217
I aggree with infinity.

I can just add : myServer->name = strup(strtemp);

wich does the same thing than malloc & strcpy
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Expert Comment

by:Infinity08
ID: 24863291
If your platform supports strdup, then that's indeed an alternative, although less portable.
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LVL 14

Expert Comment

by:flob9
ID: 24863418
Yes strdup, sorry for the typo.

And you're right for the portability :)
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