Writing from text to struct

[Clattaclism]

Well, i manage to write, somehow, to file using a struct (not as simple as i thought it would be). Now, am trying to read from the text then insert it to a srtuct. Using previous thread example

typedef struct student
{//for name
char fname[20];
char lname[20];

int age;
char id[20];
int grade[20];
}STUDENT;

the text file looks like this

andrew //firstname
magnon //lastname
12 //age
124OY //id
90 //grade

how can i write this to memory in a structure form?

please provide a code for me to follow

[leoandru]

you cant and you don't need to if you just want to read back the contents into a struct.

[Clattaclism]

y not? if u can write from a struct?

#include<stdio.h>
#include<stdlib.h> //to do the exiting

//function to save
void save(STUDENT info){
FILE *savedfile; //pointer

savedfile=fopen("c:/database.txt","w"); //creates a file on drive "c" named "database.txt" to be written to

if(savedfile == NULL) //testing if file is opened
{printf(" Error opening output file");
exit(0);} //from the library stdlib.h. will exit if file is already opened

fprintf(savedfile,"%s, %s, %d, %s, %d", info.fname,info.lname,info.age,info.id,info.grade) ;//writes struct info to file

fclose(savedfile);//closes file after writing
}

y cant something similar be done to read from text to struct?
besides, if wanted to edit the data, would i not need to do save back to memeory in a struct format?

[crosswire]

Data was loss

Before I explain, there are two ways you can approach this.

The 1st way is to serailize the struct as you have done to a binary stream. You must make sure the the write was done in binary without any loss of information. Then you can deserialize it from binary stream. When viewing the binary file, the information may have regions that are unreadable, plus not every text programs allows viewing of binary files. This method basically dumps the memory associted with the struct to the hard drive. Try to open the file in notepad or the binary editor in VS to see the contents. A precation should be taken to make sure that the struct is packed the same way for writting and reading, using #pragma pack.

The second way is carefully save each part of the struct. This I think was what the home work was about. You can save it to a compatable text file. This means no odd characters are present oout of the text character set. This method also breaks down each attribute of the struct. The unreadable binary information in the struct package is left out and only the text data is written you can even format the text as you want, doing this for each attribute, eg like putting an attribute in each new line. The text file would be easily viewable and understood, and to read the text file just reverse the process.

It depends on which method you want. BTW, binary saving does not provide encryption but it has performance for fast loading and saving. Binary is significantly more difficult to manipulate than text and you are likely to mess it up and have to do a lot of testing. It may be a better trade off to work with text save.

Summary
You would find a binary file hard to work with to maintain a database, but a text file which separated the info by new lines would be easier.

[Clattaclism]

thanks for all the info..

Crosswire, could u give an example of the second method?

and is it possible to read a line of text that contains spaces.. ive been tryin and everything have proven futile so far.

[crosswire]

//

#include<stdio.h>
#include<stdlib.h> //to do the exiting

typedef struct student
{//for name
char fname[20];
char lname[20];

int age;
char id[20];
int grade; //Correction
}STUDENT;

//function to save
void load(STUDENT & info){
	FILE *loadedfile; //pointer

	loadedfile=fopen("c:/database.txt","r"); //creates a file on drive "c" named "database.txt" to be written to

	if(loadedfile == NULL) //testing if file is opened
	{printf(" Error opening output file");
	exit(0);} //from the library stdlib.h. will exit if file is already opened

	fscanf(loadedfile,"%s", &(info.fname)) ;//writes struct info to file
	fscanf(loadedfile,"%s", &(info.lname)) ;//writes struct info to file
	fscanf(loadedfile,"%d", &(info.age)) ;//writes struct info to file
	fscanf(loadedfile,"%s", &(info.id)) ;//writes struct info to file
	fscanf(loadedfile,"%d", &(info.grade)) ;//writes struct info to file

	fclose(loadedfile);//closes file after writing
} 

void main()
{
	student	j;
	load(j);   //Place a break point here. Put j in the Debug Watch Window then click Step Over
}//

fscanf does not seem to work the scan as fprintf with the format string.

I tested once still

[Clattaclism]

Nuff respect yow. The fscanf doesnt provide much flexibility. I remanipulated the data to suit the criteria none-the-less.