how to install multiple instances of a formula?

[furrnace]

greetings, I would like to install 2 differently parameterized instances of a given formula, so that each instance has a different name and each may be used independently of each other, i.e. there is no need to uninstall the formula and to install it newly with different parameters.

can this be achieved? f so, a pointer to a document describing this would be appreciated.

[SMillerDev]

No, formula are unique by name. If you want to install the same software twice you will need to make a copy with a new name.

[furrnace]

what to you mean by "copy with a new name"? how would I do this in homebrew (do I find this in the documentation, under which chapter would that be?)

[SMillerDev]

https://docs.brew.sh/Manpage#extract---version---force-formula-tap would probably allow you to make a copy. Otherwise you can just manually copy the formula file.

[furrnace]

to make sure I understood that, is this what I need to do to have 2 instances of formula example named example-a and example-b:

brew tap my/example-a https://github.com/repouser/reponame
brew tap my/example-b https://github.com/repouser/reponame

and then to have both instances installed simultaneously, I would need to rename the formula, too, not just the tap?
how do I do this? Is it enough to just rename the .rb file or do I also need to rename the class in the first line of the .rb file? Anything else I need to do for this to work properly?

cd /usr/local/Homebrew/Library/Taps/my/homebrew-example-a
mv example.rb example-a.rb

cd /usr/local/Homebrew/Library/Taps/my/homebrew-example-b
mv example.rb example-b.rb

Questions that come to my mind (as I have zero experience with maintaining formulae):
-if the formula installs several programs, how can I make sure the program file names for instances example-a and example-b are different?
-do changes I make to the .rb file (by renaming and/or editing its content) endure a "brew upgrade --fetch HEAD my/example-a/example-a" ?

[SMillerDev]

You don't need different taps. Taps are just lists of formulae. You do need two different formulae though. That means different files and classes.

[furrnace]

I created new taps because the exctract command would not create a duplicate formula in the same tap.

How will the different formulae names lead to different names for the binaries? do I have to do something so that the binary names or the names of the links pointing to the binaries do not clash?

[SMillerDev]

That depends on the software. I can't tell you in this hypothetical scenario.

[furrnace]

lets assume we want two different instances of RfidResearchGroup/homebrew-proxmark3, one using "--with-generic" and one using "--with-blueshark"

After creating 2 new taps using the extract command I used the edit command to change the class name in both proxmark3.rb files to "Proxmark3-GENERIC" and "Proxmark3-RDV4", respectively. Also I renamed the proxmark3.rb files to proxmark3-generic.rb and proxmark3-rdv4.rb, respectively.

After that, the install command wouldn't work and complain that the options "--with-generic" or "--with-blueshark" are unknown. Obviously I missed to change something else, but I don't know what that would be.

[SMillerDev]

Well, no matter what you edit. It won't add additional commands line options to brew.

[gromgit]

in line 1 change class name from Proxmark3 to Proxmark3-RDV4 (and this should probably be Proxmark3Rdv4)

There's no "probably" about it. Failure to adhere to Homebrew's class-naming conventions will result in Homebrew not being able to find your formula's class, and therefore not be able to do anything with it.

Fix that, and see if you can make any progress.

[furrnace]

@gromgit Thank you your comment was the actual helpful one!

I now have both, proxmark3-rdv4 and proxmark3-generic, compiled and proxmark3-rdv4 is linked. I still would have to brew link --overwrite proxymark3-rdv4 or proxmark3-generic to switch between versions. As this is not really faster than doing a brew reinstall with different parameters - I haven't gained much yet.

The next step I think would be to use some brew mechanism(s) to link both formulae, proxmark3-rdv4 and proxmark3-generic, to different names in /usr/local/bin so that both are readily available in the execution path.

What is there when proxmark3-rdv4 is linked:

/usr/local/bin/pm3 -> /usr/local/Cellar/proxmark3-rdv4/HEAD-53808f2/bin/pm3
/usr/local/bin/pm3-flash -> /usr/local/Cellar/proxmark3-rdv4/HEAD-53808f2/bin/pm3-flash
/usr/local/bin/pm3-flash-all -> /usr/local/Cellar/proxmark3-rdv4/HEAD-53808f2/bin/pm3-flash-all
/usr/local/bin/pm3-flash-bootrom -> /usr/local/Cellar/proxmark3-rdv4/HEAD-53808f2/bin/pm3-flash-bootrom
/usr/local/bin/pm3-flash-fullimage -> /usr/local/Cellar/proxmark3-rdv4/HEAD-53808f2/bin/pm3-flash-fullimage
/usr/local/bin/proxmark3 -> /usr/local/Cellar/proxmark3-rdv4/HEAD-53808f2/bin/proxmark3

how could I make brew link proxmar3-rdv4 to something like /usr/local/bin/pm3-rdv4 instead of /usr/local/bin/pm3 (and likewise for proxmark3-generic: /usr/local/bin/pm3-generic instead of /usr/local/bin/pm3) ?

[gromgit]

You'd have to rename the binaries during the build itself, something like this (UNTESTED):

Dir.glob("#{bin}/*") do |f|
  File.rename "#{f}" "#{f}-rdv4"
end

[furrnace]

OK, currently I don't know yet, where in the .rb file the build section is. I am willing to learn enough about this to be able to modify the files and went to the documentation on brew.sh. To be honest, I didn't find a section that provided an entry point that was suitable for me to get an understanding of the structure of the .rb files and which "sections" are there and how to recognize them. Certainly that's my fault. I would be happy if someone could point me to a description/documentation that gives an overview of the structure of .rb files.