In bash, which history expansion re-runs the entire previous command line?
LPIC-1 Exam 101-500, objective 103. GNU and Unix commands easy
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The options
Not correct !$
Wrong. !$ expands to the LAST ARGUMENT of the previous command, e.g. after `mkdir /srv/data` you can type `cd !$`.
Correct !!
Correct. !! expands to the whole previous command line. It is most often seen as `sudo !!` after a command failed for lack of privilege.
Not correct !*
Wrong. !* expands to all the arguments of the previous command, without the command name itself.
Not correct history -c
Wrong, and destructive. history -c clears the current shell's history list rather than replaying anything from it.
Why
History expansion starts with `!`. !! is the previous command line, !n is history entry number n, !-2 is two commands back, !string is the most recent command starting with that string, and the word designators !$ and !* pull out the last argument or all arguments. `history` itself only lists or manipulates the list.
Where this comes from
- Cited
- LPI exam objective 103.1
- What it says
- Use the shell history to recall and re-run previous commands.
Practise this
Reading one question is not practice. The trainer will draw a set from objective 103 and space the ones you get wrong.