BASH: how to view command history in while loop?

Question

I have a simple while loop accepting input:

#!/bin/bash
while true; do
    read -rep $'\n '"$USER"'> ' userInput
    echo "$userInput"
done

Example:

./input.sh 

 username> command1
command1

 username> command2
command2

Is it possible to have a command history? So that I can press up on my keyboard to view the previously executed commands (without leaving the while loop)?

Answer 1

You could use the small Readline wrapper rlwrap. This is a neat little tool that provides command history to utilities that don't implement it by themselves.

You would use rlwrap on the script itself:

rlwrap -a ./script.sh

This would save a history file called ~/.script.sh_history and would use that file not only in the current session, but also in future sessions to provide a sort of history that you could step through.

See the manual for rlwrap.

rlwrap is commonly available as a package on most Unices, but may also be had from its GitHub repository.

Answer 2

You can use history -s to edit the history list, and read -e to make it possible to view the history.

#!/bin/bash
while true; do
    read -rep $'\n '"$USER"'> ' userInput
    history -s "$userInput"
    echo "$userInput"
done

Note that there are various options about the command history. The behavior may be very different between a script and an interactive shell. For example, the command history is not loaded from or saved to a file automatically in a script, which may or may not be desirable in your situation. But you can fix it by adding more code if not.