Re: Some minor notes on manual chapter 4 "Shell Builtin Commands"

[Chet Ramey]

On 10/9/23 12:25 PM, Robert Elz wrote:
>      Date:        Mon, 9 Oct 2023 10:35:20 -0400
>      From:        Chet Ramey <chet.ramey@case.edu>
>      Message-ID:  <a9e4d016-de50-4b67-a688-590ff0a77c13@case.edu>
>
>    | There is surprising variance in behavior here, from a status of 2 to 1
>    | to 0 (dash), plus the silly ksh "substitute old for new in $PWD," which
>    | the NetBSD sh (!) also performs.
>
> Yes, we do...  it is surprisingly useful behaviour, and has been there
> for a long time (Nov 2002, so it isn't going away)

Sure, if people want it there's a shell function in the bash distribution
that does the same thing using the ${var//pat/rep} expansion.

> but it doesn't really need to be in the shell, 

That's my beef, but, strictly speaking, neither do pushd/popd/dirs.

the following cd replacement func (which I use
> in bash, and other shells that don't support this) adds good enough
> support for it (not perfect, it doesn't always do the expected thing
> if the same arg string occurs multiple times in $PWD - that's very rare):

You might consider the ${param//old/new} expansion if it's available.


> ps: This is useful when you're working with lots of source trees in parallel,
> like /release/8/long/path/to/sources/being/examined and /release/9/... and
> /release/10/...   so one can just do "cd 8 9" or "cd 8 10" (etc) to switch
> from one tree to the other.  

The directory stack is good for this as well, but it can get kind of
unwieldy to keep track of what's where. I don't usually work with more
than two directories at once, for which `cd -' suffices.

Chet
--
``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/