Concatenate four binary files using alternating pattern in Linux

Question

I need to concatenate four binary, meaning non-text files. Lets say I have four files:

file1:
AAAA
file2:
BBBB
file3:
CCCC
file4:
DDDD

Now I want my resulting file to look like: ABCDABCDABCDABCD. So I want to alternate every byte. I would also like to be able to alternate every n bytes meaning alternate every 1,2,3,4,etc bytes.

So far, most of the information I searched for deals with text files and uses cat & paste which appears to only work with lines of text. I also cant find any data on alternating concatenation for more than two files.

Answer 1

This should work. Set each to the number of bytes to read each time.

len=$(stat -c %s file1)
each=1
while [ $len -gt 0 ]
do 
 dd bs=$each count=1 <&5
 dd bs=$each count=1 <&6
 dd bs=$each count=1 <&7
 dd bs=$each count=1 <&8
 let len=len-$each
done 5<file1 6<file2 7<file3 8<file4 2>/dev/null