how do I remove the last 5 lines in bash history?

You can achieve removal from the history file using the commandline in two steps:

Typing history -d <line_number> deletes a specified line from the history in memory. Typing history -w writes the current in-memory history to the ~/.bash_history file. The two steps together remove the line permanently from the in-memory history and from the .bash_history file as well.

Ref: StackExchange

There are different ways to accomplish this task, but lets clarify something before going further.

There is a file named: ~/.bash_history, which contains your older terminal sessions history, whenever you close your terminal, your history will be saved there.

At the same time the history of your old sessions along with current session is temporary accessible by history commands until you close the terminal which then will be saved into ~/.bash_history file.

So if you remove 5 lines at the end of ~/.bash_history, then closing terminal will cause your current command to be accessible at next sessions.

So if I do a wc on .bash_history:

wc -l ~/.bash_history

Most of the time I'll get a smaller number than of history | wc -l.

If you want to remove the last 5 line of the file, you can use this command:

for i in {1..5}; do sed -i '$d' .bash_history; done;

And if you want to keep all history except last 5 command issued in current session run:

history | awk '{ print $2 }' | head -n -5 > .bash_history

Don't forget to run history -c too.

I think you need to try this its very easy & simple.

1. How to delete history without any trace

   history -d $((HISTCMD-1)) && history -d NO_of_History_you_want_to_delete
   

2. if you want to excute a command without leaving any trace.

   history -d $((HISTCMD-1)) && type_your_command_here_and_execute