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Re: System() in list mode?

by ikegami (Pope)
on Oct 17, 2011 at 21:12 UTC ( #932011=note: print w/replies, xml ) Need Help??

in reply to System() in list mode?

First, it's not being called in list context. That means something else. I call this the multiple argument form.

When you use the single argument form, system expects a shell command and will launch a shell to execute the command*, so

system('echo $PATH');

is the same as

system('/bin/sh', '-c', 'echo $PATH');

The shell expands $PATH, and in turn, does

system('echo', '/foo:/bar');

which is quite different than your

system('echo', '$PATH');

You must either use the shell

system('echo $PATH');
system('/bin/sh', '-c', 'echo $PATH');

or you must do what it would do

system('echo', $ENV{PATH});

My code is supposed to set $PATH, then run a command on the same line, in the same shell.

You should start by launching a shell, then!

system('PATH=/foo prog arg');

Or not. This is something you can do yourself quite easily.

local $ENV{PATH} = '/foo'; system('prog', 'arg');

* — As an optimisation, Perl avoids launching a shell when it's obvious that the shell isn't needed.

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Re^2: System() in list mode?
by 1337John (Initiate) on Oct 18, 2011 at 15:24 UTC
    Thanks for the reply. The explanation wasn't the best but eventually I got it to work this way.

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