Though C++ problem...

[Mavrick]

I have to build a program that reads the name of an XML data file on the command line, then opens that file and processes its data.

I have already done the function that can process the data, but I cannot get the program to open the file and store it in an "istream" stream (which is required). Here's what the main() looks like:

C:\>program.exe datafile.xml

int main( int argc, char *argv[] )
{
string FileName = argv[1];

***missing code to put the data in istream***

void processData( istream& inStream ){...}
return 0;
}
So, if anybody knows how to put the content of datafile.xml into inStream so it can be processed, that would really help me!!

 

[Nothinman]

#include <fstream>

std::ifstream IN (argv[1]);

?

 

[Armitage]

What Nothingman is tersely getting at is that an istream (or actually an fstream) is what you get when you open the file. Then you use >> operator or get/getline/read to read the data from the file.

 

[Nothinman]

I was so terse because that's nearly the extent of my knowledge, I just so happened to be reading the file I/O section of GNU's libstdc++ documentation =)

My C++ skills are lacking and I'm trying to find something to cut my teeth on.

 

[Mavrick]

Thanks, going to try this right now

 

[Mavrick]

Well, now, I can load the data in the stream, but the function processData(istream& inStream) still isn't able to take the stream as an argument.

Is there a way to give a name to the istream so I can pass it as an argument or is there another way? (As I understand it, the function needs an object inStream of class istream).

 

[Mavrick]

Alright, I figured it out!!! I have to use "IN" as the argument variable.

Thanks!!

 

[Armitage]

First, you're not really loading the data into the stream. The stream object is just a file handle. It doesn't actually contain the data.

You should have no trouble passing the stream object to the function though. What does your code look like now?

 

[Armitage]

Originally posted by: Mavrick
Alright, I figured it out!!! I have to use "IN" as the argument variable.

Thanks!!

LoL, yep, passing the variable name would be a good idea!
Glad to help.

 

[Mavrick]

Originally posted by: ergeorge
First, you're not really loading the data into the stream. The stream object is just a file handle. It doesn't actually contain the data.

You should have no trouble passing the stream object to the function though. What does your code look like now?

Ooooh, ok. I wasn't really understanding why we use a stream instead of a string to store the file data up 'till now. But now I get it!! A stream is in fact just a kind of pointer between a input/output and a variable in the program/output device (screen, file).