hi,

this is my .txt file.

Read RMS voltage Register!
00980C7E
0.5939
Actual voltage!
237.5762
Read RMS current Register!
0002AEE6
0.0104
Actual current!
0.0873
Read status Register!
007FC3BC
Read RMS voltage Register!
009805E8
0.5938
Actual voltage!
237.5360
Read RMS current Register!
0002AF74
0.0104
Actual current!
0.0874
Read status Register!
007FC2D6
Read RMS voltage Register!
0097F7F8
0.5936
Actual voltage!
237.4509 ---------------------------> (i need this value)
Read RMS current Register!
0002ACE0
0.0104
Actual current!
0.0870 ------------------------> (i need this value)
Read status Register!
00920089



how do i write a c++ program to get the values?

as this text file kept updating, i need to always get the newest value (which values are insert at the bottom) will it affect the updating of the text file?

sry noob here...

What do you mean by "extract the last few lines"? Simply get the last <n> lines? Or do you want to parse them to get the data?

Also, it it really necessary to do this in C++ (that is, this is part of a larger C++ program)? Or can it also be done using shell scripting, which would probably be simpler?

the latest values are at the bottom of the text file so i need the values. i only needed 2 values, the line after "Actual voltage!" and "Actual current!".

ya this is part of a large program, so i need to use c++.

The tail command does exactly what your requirements specify. If you need to do this with your own code, it shouldn't be too hard to see how tail does it. I'm pretty sure tail is part of the binutils package, if you want to track down the sources.
--- rod.

You mean Coreutils.

any links i can read up on coreutils?

The Coreutils homepage (which could have easily been found using a search engine) will give you access to the documentation and sources.

Yes, coreutils is the correct package; thanks to Nylex for the correction. The definitive link for info would be the GNU coreutils website, or more specifically, the page for the tail utility.

--- rod.