Rename all directories after matching

Question

I'm looking for a way to rename all these directories from:

1_20_10 
1_20_20 
1_20_30 
1_20_40 

to:

2_20_10 
2_20_20 
2_20_30 
2_20_40

I tried this command:

mv /1_20*/ /2_20*/ 

and the rename command but doesn't work.

Answer 1

You can perform a substitution with sed and iterate with a for loop.

for i in 1_*; do 
   mv $i $(sed -En 's/^1_(.*)/2_\1/p' <<< $i); 
done