Re: insert-last-argument doesn't work if previous cmd is a comment

[Chet Ramey]

Nem W Schlecht wrote:

> Bash Version: 3.0
> Patch Level: 0
> Release Status: release
>
> Description:
>
>         insert-last-argument does not work if the previous command was a
> comment (starts with a '#').  At first, I thought this might be because I
> had set HISTTIMEFORMAT which inserts timestamps into the HISTFILE as a
> comment.  However, I unset HISTTIMEFORMAT and the problem still occurs.
> When I attempt to do an insert-last-argument, the shell beeps.  If I
> immediately repeat the command, the last argument from the command previous
> to the comment
>
> Repeat-By:
>
> Enter the following, assuming ESC-. is mapped to insert-last-argument
>
> $ echo hello
> $ # this is a comment
> $ echo <ESC-.>
>
>         The shell will "beep" instead of recalling the word "comment" as it
> should.

The shell (really readline; this is all standard readline behavior) is
behaving as designed.  Readline uses the history argument extraction
code to obtain the last word from the previous history entry and inserts
the result.

By default, the history code treats `#' as the history comment
character:  the character that tells it to disregard the remainder
of the line.  In this case, the entire line is not considered.

This behavior should be documented, and I will add it to the man
pages and info files.

The clumsy part of this is that there's no good way to simply
disable the history comment character.  You can set it to a
rarely-used character using an assignment to `histchars', but you
can't unset it using such an assignment.  Even unsetting histchars
resets the history characters back to their default values.

Chet