When the user is inputting commands into your shell, it should identify the left, right , up and down arrow keys. To implement this, you will need to use the termios.h library to configure a custom input strategy. Remember that after changing the configuration, you should restore it to its original configuration before exiting the program. Also, change the reads to be non-canonical and disable echoing. This will give us control on how to handle each character the user inputs. It is tricky determining which character is left, right, up or down . Most characters are only one byte long. On the other hand, the character that is output when an arrow is pressed, is three bytes long. Here are the three byte sequences for left, right, up and down arrows:

l e f t --> {27 , 91 , 68}

r i g h t --> {27 , 91 , 67}

up --> {27 , 91 , 65}

down --> {27 , 91 , 66}

 Since we are not echoing characters, you will need to echo every character the user types. If left or right key is pressed nothing should happen. But if up or down arrow key is pressed it should work as described in the History section below.