Combining a split tar file with minimal temporary disk space use

Question

I have a 400 GB tar file split into 1 GB chunks with split, like file.tar.aa, file.tar.ab, etc.

The entire .tar file can be reconstructed with cat *. I would like to unsplit the file and end up with the single 400 GB file, but I have only 15 GB free and so a simple cat * > file.tar will run out of space.

Can I do this with a minimum of temporary space?

Answer 1

Something like this would work:

#!/bin/bash                               
mv first_part.aa merged.tar             
for file in $(cat list);                                     
do                                        
cat $file >> merged.tar               
rm $file                                  
done