ActiveState and spawning commands

Eugene Tsyrklevich eugene at
Tue May 30 12:35:44 CDT 2000

On Tue, May 30, 2000 at 09:37:26AM -0700, Russ Schnapp wrote:
> ~sdpm~
> > > I assumed that if backtick and opening a pipe fail, system will 
> > > undoubtedly fail, too.  Yup -- I just tried it.
> >
> > you assumed wrong.
> Interesting.  So, you have encountered situations under which 
> backtick or pipe fails, yet "system" works?  Can you characterize 
> that situation?  It hasn't happened to me yet...

Is there a difference between 'exec "echo $arg"'  and  'exec "echo", $arg' ?
by looking at the above two statements you are probably going to say no... i mean they look almost identical, right? but there is a difference! the latter one doesn't use the shell for executing the command and is thus considered to be secure (see perlsec for more details). My point is that there are subtle differences that you might think don't make much difference but they do. the system call that i showed didn't use the shell which i thought might make a differnce (a blind guess i must confess).

quoting the perlop manpage:


       A string which is (possibly) interpolated and then executed as a system command with /bin/sh or its equivalent

so there was a difference after all...


p.s.  all of the above applies to UNIX, i don't know if it's valid in a windows world)

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