How to prevent Bash from altering history?

Question

If I press the Up or Down arrows on my keyboard and then modify something from my history, it's changed forever. Even if I press Ctrl-C and then try to bring it up again, it's still changed -- I've lost that entry in my history.

How can I prevent this from happening?

Answer 1

You want:

set revert-all-at-newline on

Which gives:

$ man bash
$ set revert-all-at-newline on
$ man bsh # up arrow and edit
No manual entry for bsh
$ man bash # three up arrows

Further details are in the manpage:

   revert-all-at-newline (Off)
          If set to on, readline will undo all changes to
          history lines before returning when accept-line is
          executed.  By default, history lines may be modified
          and retain individual undo lists across calls to
          readline.

Answer 2

I enter:

ls /tmp

- wonderful. Now I wan't to enter

ls /temp 

and can prevent it to enter the history, therefore prevent it to overwrite ls /tmp, if I start the command with a blank:

 ls /temp

It's hard to see, but if you know it ...

It is controlled by

export HISTCONTROL=ignoredups
export HISTCONTROL=ignoreboth

ignoredups only ignores duplicated commands, ignoreboth ignores spaces at the beginning of line, which is useful, to hide otherwise unhidden passwords.

But maybe you're out for a solution, where you end with both commands, the unmodified old one, and the new one. My version of bash or settings behave like this, but I don't know, what's different to yours.