An efficient way to transpose a file in Bash

Question

I have a huge tab-separated file formatted like this

X column1 column2 column3
row1 0 1 2
row2 3 4 5
row3 6 7 8
row4 9 10 11

I would like t

Answer 1

Here is a Bash one-liner that is based on simply converting each line to a column and paste-ing them together:

echo '' > tmp1;  \
cat m.txt | while read l ; \
            do    paste tmp1 <(echo $l | tr -s ' ' \\n) > tmp2; \
                  cp tmp2 tmp1; \
            done; \
cat tmp1

m.txt:

0 1 2
4 5 6
7 8 9
10 11 12

1. creates tmp1 file so it's not empty.

2. reads each line and transforms it into a column using tr

3. pastes the new column to the tmp1 file

4. copies result back into tmp1.

PS: I really wanted to use io-descriptors but couldn't get them to work.