Thanks for the quick response! I'm not really interested in learning coding, so I will proceed with the idea that someone could do this for me. And here's the answer to your questions:
Are there column headers (or anything else except data in tab-delimited rows)?
No, there are not column headers. :-( I don't even know what each of the columns are for, really, I just know some of the columns because occasionally I open the .dat files and edit the text directly. And I've figured it out over time. There is, however, always a unique identifier for each row.
What exactly needs to be merged?
The program I use is a software that keeps track of people in a tournament. It identifies each person with a unique 10 digit number. As they progress through the tournament, it stores information about how they did (win/loss/draw) and it also tracks how their opponent did each round. So the files are continuously updated throughout the day. The problem I am trying to solve is having just one person running the software. I would like to have up to 3 people running the software at a time during a round, and then at the end merge all of the .dat files from those three sources into a single master file, start the next round, and then open three copies again.
Would opening each of the files in a text editor (e.g. Notepad) and copying/pasting the entire contents of each into one file solve the problem? (I'm not asking if that would be efficient enough, just if it would produce correct results.)
I don't think it would produce the correct results. For example, if you and I are running the software together and there are 5 people in our tournament, my files would have the information for competitor #1, 3, and 5, and your files would have the information for #2 and 4. Each of us would have a full copy of the master file, so in my file there would be placeholder 0's in the #2 and 4 rows, and yours would have the placeholders in 1, 3, 5. Copying and pasting (I think) would mean that we would have 10 rows of information, and they would be out of order since each row is related to a specific person. I think what needs to happen is like an overlay - one set of files would be checked against the other, and lines with no data would be replaced with data from the other if it lined up. So in our mock scenario, the end of the merge would result in 5 rows of data in these tab columns, with rows 1, 3, and 5 coming from my file and rows 2 and 4 coming from yours. There is more than just one .dat file that needs to be merged like this each hour, too. I would have to look to be sure, but probably about 4 or 5 files total.
What OS are you on? Do you need to continuously update the merged file with new data, or can it be merged then parsed and forgotten?
I run windows 7. The program I have was built for a 32 bit system but I have a patch that forces 32 bit on my 64 bit. Yes, the files are continuously updated with new data. At the end of the day, the files will hold all of the information about the competitors and the tournament, so the files are getting added to/modified all day.