When we handle Docker or Infrastructure, we need to learn how to use lunux shell command. From now on, I'll introduce some commands we often use in common. Let's get it started.

$ whoami

This shows user id who is logined.

$ pwd

This shows current path.

$ ls -al
$ ls -al > [FILE]
$ ls -al >> [FILE]
$ head < [FILE]
$ ls -al | grep [PROCESS_NAME]

• ls -al : It shows files included hidden files.
• ls -al > [FILE] : It saves the output in a file and it can be overrided.
• ls -al >> [FILE] : It adds the output in a file.
• head < [FILE] : It shows the content of a file at line 10.
• ls -al | grep [PROCESS NAME] : It shows the list, which is included process name.

$ chmod 777 [FILE]
$ chmod 555 [FILE]
$ chmod 400 [FILE]
$ chmod 700 [FILE]

• 777 : All users can read, write and execute a file.
• 555 : All users can read, execute, but they dont' have an authroity to write.
• 400 : The owner can only read and the others don't have any authority.
• 700 : The owner has all authority, but others don't have any authority.

# ex)
$ find / -name `*.py` > list.txt
$ find / -name `*.py` > list.txt &

There is a difference between two commands. The difference is foreground process and background process.

$ ps aux | grep [PROCESS_NAME]
$ kill -9 [PID]

• ps aux : It shows the information related to process.
• kill -9 : Kill the process forcefully.

$ cp [FILE] [NEW_FILE]
$ cp -rf * [FOLDER]

-rf: It's an option to include subfolder.

$ ln [FILE] [NEW_FILE]
$ ln -s [FILE] [NEW_FILE]

• ln : It's Hard Link.
• ln -s : It's Soft Link. The size of the file, which is connected to soft link, is smaller than the original.

Wrap Up

If I find something useful, I'll share it with you guys here. Let's call it a day.