I recently switched from tcsh to bash, and one thing that keeps tripping me up is how bash handles history. I regularly bring up a previous history command and begin to edit it, but realize I need to run a different command first. In bash, this edits the original command, and I cannot see what I originally typed. In tcsh, the edited command is at the bottom of the stack when I use the up and down arrows, and is ready to continue editing or run when I am ready for it.
I found this question, which had several answers helpful in understanding how bash works in regards to rerunning and editing history, but I still don’t know of a way to change this behavior (if such a thing exists). Is it possible to prevent bash from editing the commands that have already been run?
For example, if I run
abcd efgh ijkl
And then use arrow up and backspace efgh to efg, then hit down and type a different command “mnop”, I want my history to look like:
abcd efgh ijkl mnop
Currently it looks like:
abcd * efg ijkl mnop
This may seem like a trivial issue but when running long commands with multiple pipes that require trial and error, it is some substantial loss of work.
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Answer
Each line maintains its own undo list which you can access with C-x C-u or C-_ to undo the most recent change, or M-r to revert all changes since it was last saved.