editing text you typed in seems so basic:

>>> print("helo")

oops, forgot an l!

but there’s actually no standard system

programs need to implement even the most basic things

Illustration of a little smiling stick figure with curly hair.

person: “left arrow”

program, represented by a box with a smiley face: “ok I will move the cursor to the left”

often programs will use the readline library for this

option 1: NOTHING

person (angry): “even the ARROW KEYS don’t work???”

program (blissfully content): arrow keys? what’s that?

• Only Ctrl-W Ctrl-U and backspace work
• Examples: cat, nc, git
• You’re probably in this situation if you press the left arrow key and it prints ^[[D
• You can often add readline shortcuts with rlwrap, like this:

$ rlwrap nc

option 2: READLINE

person (neutral): “it’s a little awkward but at least I can use those weird keyboard shortcuts from emacs!”

• LOTS of keyboard shortcuts: Ctrl-A Ctrl-E , arrow keys, many more
• You can use Ctrl-R to look at history
• Examples: bash, irb, psql
• If you press Ctrl-R and you see “reverse-i-search” , you’re probably using readline
• Configurable with the ~/.inputrc config file

option 3: CUSTOM

person (smiling): “wow, I can type a multiline command without it being a total disaster?? amazing!”

• The keyboard shortcuts are probably influenced by readline
• Examples: fish, zsh, ipython
• usually you only see custom implementations in bigger projects