todo

[cat] Run and understand the behavior of the end of the last line of a file

[diff] Run and understand. Show differences between files.

[Shell] Run and understand command substitution output

[awk] Run and understand Using the trigonometric functions sin and cos

[type] Run and understand Display the executable path of the command

[bash] Run and understand: Run a shell script with read-only permissions

[find] Run and understand Find and execute shell scripts

[echo] Run and understand. Interpret and output string escapes.

[sed] Run and understand Replace nth arbitrary string in each line

[Shell] Run and understand: Use heredoc to input while statement