getting data from file

**task** · 06-19-2003

I am not sure of the best wat to get my data from a file and convert it into it correct data type.

I have used fgets(); to get the line of data but I am not sure of the best way of converting it the data can be of diffrent types which is determined by the first character. My problem is that the string then wants breaking down in to various fields
i.e. one of the types is as follows :
the record type ( 1 character )
the customer code (5 characters ) convert to numeric
the customer name ( upto 20 characters ) may contaon spaces
the customer address( upto 60 characters) seperated by 4 ; and may contain spaces
the Customer balance( 9 characters) to become floating point
and the Credit limit ( 7 characters) convert to numeric

what is the best way to disect the string into the individual elements

Thanx in advance

**mart_man00** · 06-19-2003

have you looked at strtok?

**mart_man00** · 06-19-2003

good point i didnt notice the "may contaon spaces" part till now. if it the programs file and not something the user has to deal with he could come up with something unique to be a delimiter. just a n00b's idea..........

**WaltP** · 06-19-2003

Originally posted by task
I am not sure of the best wat to get my data from a file and convert it into it correct data type.

I have used fgets(); to get the line of data but I am not sure of the best way of converting it the data can be of diffrent types which is determined by the first character. My problem is that the string then wants breaking down in to various fields
i.e. one of the types is as follows :
the record type ( 1 character )
the customer code (5 characters ) convert to numeric
the customer name ( upto 20 characters ) may contaon spaces
the customer address( upto 60 characters) seperated by 4 ; and may contain spaces
the Customer balance( 9 characters) to become floating point
and the Credit limit ( 7 characters) convert to numeric

what is the best way to disect the string into the individual elements

Thanx in advance

Create a structure that defines the format of the line. But keep in mind the Customer balance is 9 characters and not a string because it is not null-terminated. You'll have to convert the values by hand.

If the first character defines the format of the rest of the line, you may want to use a union -- it can use multiple structures to define the same input space.

**task** · 06-20-2003

What's the delimiter between name and address?

It is part of my coursework and I have read through it and it doesn't say, I am assuming that if the name occupies less than 20 characters the rest will just be whitespaces.

**mart_man00** · 06-20-2003

is there anything saying your data file cant look like this

"name","address"

or even

<name><address> ?

that would give you something unique and if its just the data file the user wouldnt have to see it. you could just strtok for " or <>s and then run threw what it gives you. there might be a better way, but this should be simple.

**task** · 06-20-2003

I don't produce the data the college does so I cant incorporate anthing into the data. so the data must be stored in the file as 1character for type than 20 characters for the name ( i.e. if name is only 10 characters it is followed by 10 spaces) to fill the 20 characters allowed and then the address starts and so on.

**task** · 06-20-2003

yes that is as I understand it

**quzah** · 06-20-2003

Originally posted by task
yes that is as I understand it

Ok then, read 20 bytes and stick it in the name block, then continue from there to read whatever is next.

Quzah.

**task** · 06-20-2003

I am not sure of how to do this as both the name and address may contain spaces i.e 123 street not 123_street or something like that. I dont want it to stop reading the data when it encounters a white space but other than using a function that only picks up one character each time it is called I am not sure how to do it.

**Hammer** · 06-20-2003

Read the complete line into one temporary buffer using fgets(), then pluck out the bits you want. If the input data is properly structured, and you're not worried about validation, it should be quite easy to do.

Start by creating a struct to hold your data in, then learn how to populate it bit by bit. When you have some code together, post it here and someone will help you.

**task** · 06-20-2003

Code:

int make_fields( char *string_ptr, RECORD *data_ptr )
{
   if( sscanf( string_ptr, "%c%5s%21s%61s%10s%8s", 
                              &data_ptr->Cre.Record_Type,
	              data_ptr->Cre.Customer_Code,
	              data_ptr->Cre.Customer_Name,
	              data_ptr->Cre.Customer_Address,
                              data_ptr->Cre.Customer_Balance,
	              data_ptr->Cre.Credit_Limit) != 6 )
		
        return ERROR;
   else
        return VALID;
}

The function is passed the address of the temporary string that took the line of data from the file using fgets() and RECORD *data_ptr points to the union that contains the various structures I require including the (Cre )one that I need for the example.

am I close on this or a million miles off?

**quzah** · 06-20-2003

Looks fine, other than the possible problem with sscanf and your variables. If any of those are not character arrays, then you'll need to modify the call to use the address of said variable. Consider:

Code:

struct foo
{
    int bar;
};

struct foo f, *b;

b = &f;

scanf("%d", &b->bar );

You need the address symbol here to scan into the integer itself. You may be aware of this, but this is the only potential problem I can see, since you didn't provide the structure definition for us to look at.

Quzah.

**Hammer** · 06-20-2003

Looks ok at a glance. Why not write a smaller main() to invoke and test it, and see if it does what you want.

[edit]Doh, beaten.

**task** · 06-20-2003

Looks fine, other than the possible problem with sscanf and your variables. If any of those are not character arrays, then you'll need to modify the call to use the address of said variable. Consider:

code:--------------------------------------------------------------------------------
struct foo
{
int bar;
};

struct foo f, *b;

b = &f;

scanf("%d", &b->bar );

I was just going to create copies of them in diffrent formats as I need to store them back in file afterwards.
i.e.

[code]

int temp_balance;

temp_balance = atol( data_ptr->Cre.Customer_Balance );

/* Then validate it here */

[\code]

Is this o.k. or not good practice

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