Extracting information of data in column format using C++

[Leonardo Machado]

Hello friends, how are you ?

Today's question is: How do i choose the data i want to extract from a file in c++ ?

I have this data file in columns format, something like:

x      y      z
1      2      3
4      5      6
7      8      9

I know there is the command file.getline() , and this command can be manipulated to get the string the size i want, but there is a way of skip the space between the numbers and catch only the data of the second column?

And plus, there are any way to get it not in str format ? but in a float or a double format ?

Thanks for the tips

 

[DrClaude]

What about the >> operator?

 

[Leonardo Machado]

What about the >> operator?

Could you give any example of using >> ?
It works like cin, right ? But how do i command it to get information of an specific line and column ?

 

[DrClaude]

Could you give any example of using >> ?
It works like cin, right ? But how do i command it to get information of an specific line and column ?

It works with cin. or any istream. Each >> will read data until it reaches a blank space, so columns are easy to take care of.

I'm sure you can find good examples online.

 

[Leonardo Machado]

It works with cin. or any istream. Each >> will read data until it reaches a blank space, so columns are easy to take care of.

I'm sure you can find good examples online.

Got it, thanks mate, it worked for me.

Just for finishing, how do i reset the command ? For start to read the first line again ?

 

[Mark44]

Just for finishing, how do i reset the command ? For start to read the first line again ?

Close the file and open it again. The position-in-file pointer will now be at the start of the file.

The C standard library (as opposed to the C++ Standard Library) has a rewind() function. With this function you don't have to close and then reopen the file.

The C++ basic_filebuf class has a seekpos() function. You can use it to move the position-in-file pointer to a selected location in the file -- to the beginning or to the end, or to some point within the file. There is also a seekoff() function that can be used for a similar purpose.

 

[Leonardo Machado]

Close the file and open it again. The position-in-file pointer will now be at the start of the file.

The C standard library (as opposed to the C++ Standard Library) has a rewind() function. With this function you don't have to close and then reopen the file.

The C++ basic_filebuf class has a seekpos() function. You can use it to move the position-in-file pointer to a selected location in the file -- to the beginning or to the end, or to some point within the file. There is also a seekoff() function that can be used for a similar purpose.

Thanks for the attentions, Mark44 and DrClaude. I'm grateful.

 

[newjerseyrunner]

Personally, I'd read the entire thing into a buffer, then parse it into a data structure. That way you can later do something like:

item = chart.x(0);