Parameter subsitution

Parameter subsitution

[Lewis Butler]

Reading through the docs:

The s/l/r/ substitution works as follows. 
 [. . . ]
* A null l uses the previous string either from the previous l or from the contextual scan string s from ‘!?s’. 

And

* Note the same record of the last l and r is maintained across all forms of expansion.

Does this mean that l is recorded until the shell terminates or until a new l is used? Is there a way to see what the current l is set to?

$ file="/usr/local/tmp/filename.txt"
$ echo ${file:s|e|3}
/usr/local/tmp/fil3name.txt
$ echo ${file:s||4}
/usr/local/tmp/filename.txt

Doesn't look like the l is maintained?

And where is the !?s syntax defined?

Any examples of using !?s in anger?

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Re: Parameter subsitution

[Bart Schaefer]

On Fri, Jan 8, 2021 at 2:02 PM Lewis Butler <lbutler@covisp.net> wrote:
>
> The s/l/r/ substitution works as follows.
>  [. . . ]
> * A null l uses the previous string either from the previous l or from the contextual scan string s from ‘!?s’.
> * Note the same record of the last l and r is maintained across all forms of expansion.
>
> Does this mean that l is recorded until the shell terminates or until a new l is used?

Until a new l is used.

> Is there a way to see what the current l is set to?

No.

> $ file="/usr/local/tmp/filename.txt"
> $ echo ${file:s|e|3}
> /usr/local/tmp/fil3name.txt
> $ echo ${file:s||4}
> /usr/local/tmp/filename.txt
>
> Doesn't look like the l is maintained?

Works for me:

ubuntu% file=filename
ubuntu% print ${file:s/e/3}
fil3name
ubuntu% print ${file:s//4}
fil4name
ubuntu% print ${file:s||5}
fil5name
ubuntu%

> And where is the !?s syntax defined?

History expansion, under Event Designators.

> Any examples of using !?s in anger?

What are you talking about!?

Re: Parameter subsitution

[Lewis Butler]

On 08 Jan 2021, at 15:25, Bart Schaefer <schaefer@brasslantern.com> wrote:
>> Any examples of using !?s in anger?
> 
> What are you talking about!?

<https://www.ldoceonline.com/dictionary/do-use-something-in-anger>
do/use something in anger
humorous to do or use something in a real situation


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Re: Parameter subsitution

[Bart Schaefer]

On Fri, Jan 8, 2021 at 2:31 PM Lewis Butler <lbutler@covisp.net> wrote:
>
> On 08 Jan 2021, at 15:25, Bart Schaefer <schaefer@brasslantern.com> wrote:
> >> Any examples of using !?s in anger?
> >
> > What are you talking about!?

Obviously my own attempt to be silly went wide of the mark.

> humorous to do or use something in a real situation

% vi foo.c foo.h
... several commands ensue ...
% !?foo.h?:gs/foo/bar
vi bar.c bar.h

Re: Parameter subsitution

[Lewis Butler]

On 08 Jan 2021, at 15:53, Bart Schaefer <schaefer@brasslantern.com> wrote:
> On Fri, Jan 8, 2021 at 2:31 PM Lewis Butler <lbutler@covisp.net> wrote:
>> 
>> On 08 Jan 2021, at 15:25, Bart Schaefer <schaefer@brasslantern.com> wrote:
>>>> Any examples of using !?s in anger?
>>> 
>>> What are you talking about!?
> 
> Obviously my own attempt to be silly went wide of the mark.

Text is not always the best medium for silliness 😃

>> humorous to do or use something in a real situation
> 
> % vi foo.c foo.h
> ... several commands ensue ...
> % !?foo.h?:gs/foo/bar
> vi bar.c bar.h

Ah, yes, I can see where that would be useful. I often (used to) do things in bash like `^string^replace` (I think that's right) but was frustrated that only replaced the first occurance and only in the previous command, so I got used to using up-arrow to get the command I wanted and then just manually editing.

Wonder why my zsh is not behaving as your with the recalling of l in the substation though.

$ zsh --version
zsh 5.8 (x86_64-apple-darwin20.0)

Maybe something in oh-m-z?

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Re: Parameter subsitution

[Lawrence Velázquez]

> On Jan 8, 2021, at 6:46 PM, Lewis Butler <lbutler@covisp.net> wrote:
> 
> Ah, yes, I can see where that would be useful. I often (used to)
> do things in bash like `^string^replace` (I think that's right)

Note that zsh recognizes ^foo^bar as well, and bash recognizes !?foo.

> Wonder why my zsh is not behaving as your with the recalling of l
> in the substation though.
> 
> $ zsh --version
> zsh 5.8 (x86_64-apple-darwin20.0)
> 
> Maybe something in oh-m-z?

Perhaps omz is doing its own history expansions that make using a
null pattern on your command line untenable.

vq

Re: Parameter subsitution

[Bart Schaefer]

On Fri, Jan 8, 2021 at 4:00 PM Lawrence Velázquez <vq@larryv.me> wrote:
>
> > On Jan 8, 2021, at 6:46 PM, Lewis Butler <lbutler@covisp.net> wrote:
> >
> > Wonder why my zsh is not behaving as your with the recalling of l
> > in the substation though.
> >
> > Maybe something in oh-m-z?
>
> Perhaps omz is doing its own history expansions that make using a
> null pattern on your command line untenable.

That was my thought as well.  There may be a ${...:s...} in precmd or some such.

Re: Parameter subsitution

[Lewis Butler]

On 08 Jan 2021, at 17:00, Lawrence Velázquez <vq@larryv.me> wrote:
>> On Jan 8, 2021, at 6:46 PM, Lewis Butler <lbutler@covisp.net> wrote:
>> 
>> Ah, yes, I can see where that would be useful. I often (used to)
>> do things in bash like `^string^replace` (I think that's right)
> 
> Note that zsh recognizes ^foo^bar as well,

Yep, but I stopped using it years and years ago, long before I used zsh. Heck, before I used bash4.

> and bash recognizes !?foo.

bash versions greater than 3.x?

But I am not using bash anywhere now other than in some shell scripts that didn't work with zsh and I didn't take the time to figure out why

>> Wonder why my zsh is not behaving as your with the recalling of l
>> in the substation though.
>> 
>> $ zsh --version
>> zsh 5.8 (x86_64-apple-darwin20.0)
>> 
>> Maybe something in oh-m-z?
> 
> Perhaps omz is doing its own history expansions that make using a
> null pattern on your command line untenable.

Probably. I'll test without oh-m-z at some point.

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