bash(というよりLinuxコマンド)強化週間。
https://cmdchallenge.com/

1

Your first challenge is to print “hello world” on the terminal in a single command.

printf 'hello world' 

2

Print the current working directory.

pwd

3

List names of all the files in the current directory, one file per line.

ls | grep '' 

lsを行った時点では1行につき1ファイル表示にならないが、grepに渡した後は1行につき1ファイル表示になる。

4

There is a file named access.log in the current directory. Print the contents.

cat access.log 

5

Print the last 5 lines of “access.log”.

tac access.log | head -n 5 | tac 

tac(catの逆)を2回使って戻している。

6

Create an empty file named take-the-command-challenge in the current working directory.

touch take-the-command-challenge 

7

Create a directory named tmp/files in the current working directory

mkdir -p tmp/files

pはparents。

8

Copy the file named take-the-command-challenge to the directory tmp/files

cp take-the-command-challenge tmp/files 

9

Move the file named take-the-command-challenge to the directory tmp/files

mv take-the-command-challenge tmp/files 

10

Create a symbolic link named take-the-command-challenge that points to the file tmp/files/take-the-command-challenge.

ln -s tmp/files/take-the-command-challenge take-the-command-challenge

11

Delete all of the files in this challenge directory including all subdirectories and their contents.

find . -delete  

たった一つのオプションをつけるだけでfindは恐ろしいコマンドになる。

参考