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Re: Issues with history substitution and its documentation

From: Chet Ramey
Subject: Re: Issues with history substitution and its documentation
Date: Mon, 18 Nov 2019 10:34:47 -0500
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:68.0) Gecko/20100101 Thunderbird/68.2.2

On 10/3/19 6:19 PM, Jim Monte wrote:

Documentation of quick substitution is incorrect (or does not match

I believe this issue is an error with the documentation of history
"Quick Substitution" that has existed since the first snapshot available at
web.archive.org in 2007 at


At the least it is true that bash does not behave as the documentation
but it does act in a way that is more reasonable (to me) than what is

The documentation states that ^string1^string2^ is equivalent to
!!:s/string1/string2/. However, bash treats it as equivalent to

This is correct, and I changed the documentation.

Behavior of empty "old" string in a substitution is undefined.

The earlier example also shows a related but different issue with the
!!:s//a/b/ command, where the string to locate is empty.
It causes /a to be replaced by a and the b/ is appended.

It's not, actually. It's documented in the man page, but due to an
oversight the text doesn't appear in the texinfo manual.

If an event designator has a leading - character, it is ignored.

It's treated as an offset with value 0, and otherwise ignored. If it's not
followed by a digit string, it should be treated as part of a search


``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    address@hidden    http://tiswww.cwru.edu/~chet/

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