RIS files I think are just text files. Can you open in a text editor and paste the content of one into another. Of course you should only do this with copies of your original files. Also why would you want to do this. If you import both files into a reference manager e.g. Zotero or Mendeley you can organise references and delete duplicates that way. BW Matt
If you're using Windows, the "copy" command should help (files should be in the same folder), using a Command prompt:
copy *.ris db.ris
If you're using Ubuntu Linux and can move all the ris files inside a folder, just open a terminal in the folder and use "cat":
cat *.ris > db.ris
There are more complex commands, but you can move files in a folder easily if you search for them by extension and cut/paste.
The files are basic text files, so it works for other text files of interest (i.e. CSV).
I used this to import some stuff to my JabRef database... seems like the new version of JabRef doesn't like Drag&Drop and can't select multiple files for import.
p.s. there's a lovely extension for browsers called: BibItNow
Dragomir Dan Sângeorzan your answer was golden and saved me so much time that it would've taken to manually combine 80 RIS files or upload each to a reference manager!! I used the cat command as you recommended, and it worked. I uploaded one combined RIS file with no problems. Thank you.
The ris file is a txt file. you can merge many ris files in windows command line. Open the folder containing the files to be merged in the file manager. Press ⇧ Shift as you right-click a blank area of the right panel. A context menu will expand.Click Open command window here. This opens a command prompt window that's already set to the current directory.Type copy *.ris newfile.ris at the prompt. all file will merged in new file "newfile.ris"