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From: Jim Monte <jim.monte01@gmail.com>
Newsgroups: gnu.bash.bug
Subject: Re: Issues with history substitution and its documentation
Date: Mon, 18 Nov 2019 13:10:37 -0500
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Approved: bug-bash@gnu.org
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To: Chester Ramey <chet.ramey@case.edu>
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Thanks again for looking at these reports. I have thankfully essentially
completed my implementation of history for ngspice (an open-source
successor to SPICE 3F5 with a csh-like front end that handles parsing a bit
differently than a shell would), so I believe this report will be the final
one.

Jim

Related to the other report, there is some more missing documentation
regarding the :s word modifier.

If the line ends after "old", it is equivalent to :s/old/new/ (assuming old
and new do not contain '/').
If the line ends after the first delimiter, it is equivalent to :s///,
i.e., the previous old pattern is used and new is an empty string.
If the line ends after :s, no action is performed.
[root@localhost ~]# echo a b c
a b c
[root@localhost ~]# echo !:s/a
echo echo  b c
echo b c
[root@localhost ~]# echo a b c
a b c
[root@localhost ~]# echo !:s/
echo echo  b c
echo b c
[root@localhost ~]# echo a b c
a b c
[root@localhost ~]# echo !:s
echo echo a b c
echo a b c

Jim

On Mon, Nov 18, 2019 at 11:14 AM Chet Ramey <chet.ramey@case.edu> wrote:

> On 11/3/19 9:18 AM, Jim Monte wrote:
> > Two more documentation issues I have found are below.
> >
> > It appears that an empty substring event designator uses the string of
> the
> > previous substring event designator if none is provided and does not find
> > the event if there is no previous string.
>
> Thanks for the report. I'll add text documenting the behavior. (FWIW, csh
> doesn't document it, either.)
>
>
> > An empty "old" string in a substitute word modifier uses the previous
> "old"
> > if none is given, but uses an empty string if new is empty. If there was
> no
> > previous "old" string, an error is reported.
>
> As I said in a previous message, this is documented in the man page but
> omitted in the texinfo manual.
>
>
> --
> ``The lyf so short, the craft so long to lerne.'' - Chaucer
>                  ``Ars longa, vita brevis'' - Hippocrates
> Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/
>