How about an actual flag in__construct or a named constructor? IIRC! and!! had a meaning in shell. While their usage via Process component can be questioned, it is still changing original behaviour.

EDIT: also not knowing about the opt-in process I'd pull my hair out why the command is prefixed with a!.

the constructor is already overloaded with arguments,
what meaning does! have? to me, it's only for interactive use.
can you give an example?

what meaning does ! have? to me, it's only for interactive use.

It might have been for interactive usage only,!! is rerunning last command, not sure if it requires interactive or not. But interactive or not, reading the command as a new comer I would wonder why shell command is prepended with a!.

the constructor is already overloaded with arguments,

Then we can go with a named constructor:Process::prepared($commandline, string $cwd = null, array $env = null, $input = null, ?float $timeout = 60) which would hide away the additional flag in the original__construct. Also this will clearly indicate that one is about to use prepared command.

@malarzm would you like to lead this effort? it feels like you might want to help :) If so, I invite you to borrow this PR and make the patch yours. Should be done using eggit fetch git@github.com:symfony/symfony refs/pull/26344/head:prepared-process. About your comment for a named constructor, you'll also need to deal with theProcess::setCommandline() method.

It looks like enough people are interested into working on this and have ideas different than mines.
That's really great, no need for me here :)
As I'm on holiday next week, I won't be able to further work on this.
Please take over.

I’m taking over,@Tobion could you please crate an issue and ping me in it so we won’t forget ?

Just one last note: don't be fooled, the feature at glance isnot about writing prepared command lines.
Prepared command lines are already possible since 3.3.

Here is one that works on 3.3:
(new Process('echo "$FOO"'))->run(null, array('FOO' => 123));

The feature at glance is theportability of prepared command lines, as on Windows, the same has to be written as:
(new Process('echo !FOO!'))->run(null, array('FOO' => 123));

That's why I resisted creating any new API (and I'm still dubious about the need for any): writing aportable prepared command line should be easier than using a ternary operator, which is all what is needed to achieve portability on 3.3.

Sure, I'll try to prepare a PR tomorrow unless@Simperfit beats me to it ;)