> On 2018 Jan 21 , at 7:13 a, Ralph Corderoy <ra...@inputplus.co.uk> wrote:
>
> Hi,
>
> Please keep me CC'd.
>
> bash package 4.4.012-2 on Arch Linux,
> `version 4.4.12(1)-release (x86_64-unknown-linux-gnu)'.
>
> I'm trying to enable history expansion in a non-interactive bash with
> `set -H'.
>
> $ printf '%s\n' ': foo' 'echo !!' 'set -H' ': bar' 'echo !!' |
>> bash
> !!
> !!
> $
>
> I'd expect the second `!!' to be `: bar'.
> What am I misunderstanding?
You enabled history *expansion*, but not the history mechanism itself, so there
is nothing for !! to expand to. You need `set -o history` as well.
$ printf '%s\n' ': foo' 'echo !!' 'set -H -o history' ': bar' 'echo !!' |
bash
!!
echo : bar
: bar
The second line, 'echo : bar', is the result of the expansion itself, prior to
the resulting command actually being executed.
