在bash中选择随机目录的脚本

Question

I have a directory full of directories containing exam subjects I would like to work on randomly to simulate the real exam.

They are classified by difficulty level:

0-0, 0-1 .. 1-0, 1-1 .. 2-0, 2-1 ..

I am trying to write a shell script allowing me to pick one subject (directory) randomly based on the parameter I pass when executing the script (0, 1, 2 ..).

I can't quite figure it, here is my progress so far:

ls | find . -name "1$~" | sort -r | head -n 1

What am I missing here?

Answer 1

There's no need for any external commands ( ls , find , sort , head ) for this at all:

#!/usr/bin/env bash
set -o nullglob       # make globs expand to nothing, not themselves, when no matches found
dirs=( "$1"*/ )       # list directories starting with $1 into an array

# Validate that our glob actually had at least one match
(( ${#dirs[@]} )) || { printf 'No directories start with %q at all\n' "$1" >&2; exit 1; }

idx=$(( RANDOM % ${#dirs[@]} ))  # pick a random index into our array
echo "${dirs[$idx]}"             # and look up what's at that index