Chapter 7 Linux Command Line Interface (CLI)

This document covers basic linux shell commands used frequently when working with Ubuntu’s Command Line Interface (CLI).

7.1 Getting Help Documentation

[command] --help: Gets you the help documentation for a particular command including a list of the options and usage.

mkdir : Used to create a directory if not already exist. It accepts directory name as input parameter
cp : This command will copy the files and directories from source path to destination path. It can copy a file/directory with new name to the destination path. It accepts source file/directory and destination file/directory.
mv : Used to move the files or directories. This command’s working is almost similar to cp command but it deletes copy of file or directory from source path.
rm : Used to remove files or directories.

cat: It is generally used to concatenate the files. It gives the output on the standard output.
head: Used to print the first N lines of a file. It accepts N as input and the default value of N is 10. head -6 file.txt will show the first 6 lines of a file.
tail: Used to print the last N-1 lines of a file. It accepts N as input and the default value of N is 10. tail -6 file.txt will show the last 5 lines of a file.

sudo: Requried for performing actions that require root or superuser permissions.
chmod: Change the access permissions of files and directories. Common Codes:
- Code List:
  - 0: No permission
  - 1: Execute permission
  - 2: Write permission
  - 3: Write and execute permissions
  - 4: Read permission
  - 5: Read and execute permissions
  - 6: Read and write permissions
  - 7: Read, write and execute permissions
- 777 to make file readable, executable, and writable by:
  - User = 7: read, execute, write
  - Group = 7: read, execute, write
  - Other = 7: read, execute, write
- 755 to give everyone read/execute and make file owner permission to write to the file.
  - User = 7: read, execute, write
  - Group = 5: read, execute
  - Other = 5: read, execute

Applies to Mac/Linux users. Windows users will use Putty.

ssh - Go to AWS EC2 instance and select “Connect”. You will get a connection string.
exit - Exits the AWS EC2 Terminal