How to create 100 subdirectories using a Bash script?

The easiest way is probably to use brace expansion

mkdir subdirectory_{1..100}

To answer your question using your suggested for loop - the brace expression mentioned by steeldriver works as well:

for i in {1..100}; do mkdir subdirectory_$i; done

To answer your updated question:

Both - the answer by steeldriver and the one by me are both meant to be one-liners.

If you would want to use this in a Bash script, you'd probably write it like:

#!/bin/bash
for i in {1..100}
do
    mkdir subdirectory_$i
done

To add a little something to the truly impressive answer given by steeldriver:

You can create directories that sort "properly" by padding with zero.

mkdir subdirectory_{001..100}

(If you like this answer, please upvote steeldriver's answer. I cannot yet comment, or would have done so.)

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