Preserve command history in chronological order (in fish)

Question

I have noticed that default behaviour for storing command history is only storing the latest entry. Typing ls and then ls -al and then entering history would show:

ls -al
ls

Typing ls once more would then show:

ls
ls -al

All other occurances of these commands in the command history are now gone. This makes it hard to relearn a process I may have done a few days ago.
Is there a way to make fish preserve every command entry in the same order as they are entered?

Answer 1

There's no configuration to do this automatically with the history function itself, no. From the Fish docs:

Any duplicate history items are automatically removed.

However, if the goal is simply to capture the what you entered so that you can review the commands later (in the proper context), that's it's entirely possible via scripting. At a simple level, what you want to do is simply save every command entered at the prompt into a file that doesn't remove duplicates.

Create the following function in ~/.config/fish/conf.d/save_full_history.fish:

function log_command --on-event fish_preexec
    echo $argv[1] >>  ~/.local/share/fish/fish_full_history
end

That does a few things:

• By having it in ~/.config/fish/conf.d, it will automatically load the function every time Fish starts. This is done through conf.d since --on-event (and other) hooks aren't activated in lazy-loaded Fish functions.
• Using the --on-event fish_preexec, the function runs just after Enter is pressed for each command.
• The function receives the full commandline that was entered as $argv[1], saving it to the ~/.local/share/fish/fish_full_history file for future review.

You could, of course, add something like a timestamp to this. E.g.:

echo $(date --iso-8601=ns) --- $argv[1] >>  ~/.local/share/fish/fish_full_history

You could also create a separate function (it can be in the same file) that executed on fish_posterror to make a note in the file when the command resulted in an error.