Re: Using && in commands

[Robert Mecklenburg]

From: "Noel Yap" <address@hidden>
> IIRC, make will spawn a shell for the sed command due to to '>' in the
> command line.  I believe make will then fork/exec for the mv command.
> Since make is already shelling out for the sed command, I see no reason
> not to use that shell to do the conditional mv as well.
>
> If you're worried about legibility, you could write the rule as:
>
> foo:
> sed ... > /tmp/x  && \
> mv /tmp/x y

Good thinking, I hadn't considered performance.

But I'm not sure I agree.  The two command version will fork/exec three
times 1) make forks bash; 2) bash forks sed; 3) make forks mv.  The &&
version also forks three times 1) make forks bash; 2) bash forks sed; 3)
bash forks sed.  I'm not sure I see a performance argument.

I do see a clarity argument (not only legibility).  Make's job is to ensure
a command has finished with success before starting the next command.  Why
use a (slightly) arcane syntax of the shell when the "obvious" command is
intended to work?  I'm still mulling this over.

More thoughts?
Robert