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Perl Programming Language

FAQ 8.28 How can I call backticks without shell processing?


This is an excerpt from the latest version perlfaq8.pod, which
comes with the standard Perl distribution. These postings aim to
reduce the number of repeated questions as well as allow the community
to review and update the answers. The latest version of the complete
perlfaq is at http://faq.perl.org .

--------------------------------------------------------------------

8.28: How can I call backticks without shell processing?

    This is a bit tricky. You can't simply write the command like this:

            @ok = `grep @opts '$search_string' @filenames`;

    As of Perl 5.8.0, you can use open() with multiple arguments. Just like
    the list forms of system() and exec(), no shell escapes happen.

            open( GREP, "-|", 'grep', @opts, $search_string, @filenames );
            chomp(@ok = <GREP>);
            close GREP;

    You can also:

            my @ok = ();
            if (open(GREP, "-|")) {
                    while (<GREP>) {
                            chomp;
                            push(@ok, $_);
                }
                close GREP;
            } else {
                    exec 'grep', @opts, $search_string, @filenames;
            }

    Just as with system(), no shell escapes happen when you exec() a list.
    Further examples of this can be found in "Safe Pipe Opens" in perlipc.

    Note that if you're use Microsoft, no solution to this vexing issue is
    even possible. Even if Perl were to emulate fork(), you'd still be
    stuck, because Microsoft does not have a argc/argv-style API.

--------------------------------------------------------------------

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are not necessarily experts in every domain where Perl might show up,
so please include as much information as possible and relevant in any
corrections. The perlfaq-workers also don't have access to every
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Working code is greatly appreciated.

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--
Posted via a free Usenet account from http://www.teranews.com

On May 30, 3:03 pm, PerlFAQ Server <b@stonehenge.com> wrote:

> 8.28: How can I call backticks without shell processing?

>     Note that if you're use Microsoft, no solution to this vexing issue is
>     even possible. Even if Perl were to emulate fork(), you'd still be
>     stuck, because Microsoft does not have a argc/argv-style API.

s/use/using/;
s/a argc/an argc/;

--
Brad

On 31 May 2007 06:02:32 -0700, Brad Baxter <baxter.b@gmail.com>
wrote:

>>     Note that if you're use Microsoft, no solution to this vexing issue is
>>     even possible. Even if Perl were to emulate fork(), you'd still be
>>     stuck, because Microsoft does not have a argc/argv-style API.

>s/use/using/;
>s/a argc/an argc/;

Incidentally, doesn't perl now emulate fork under Windows?

  C:\temp>perl -le "print fork"
  -948
  0

Michele
--
{$_=pack'B8'x25,unpack'A8'x32,$a^=sub{pop^pop}->(map substr
(($a||=join'',map--$|x$_,(unpack'w',unpack'u','G^<R<Y]*YB='
.'KYU;*EVH[.FHF2W+#"\Z*5TI/ER<Z`S(G.DZZ9OX0Z')=~/./g)x2,$_,
256),7,249);s/[^\w,]/ /g;$ \=/^J/?$/:"\r";print,redo}#JAPH,

In article <1180616552.861311.309@g4g2000hsf.googlegroups.com>, Brad

Baxter <baxter.b@gmail.com> wrote:
> On May 30, 3:03 pm, PerlFAQ Server <b@stonehenge.com> wrote:
> > 8.28: How can I call backticks without shell processing?

> >     Note that if you're use Microsoft, no solution to this vexing issue is
> >     even possible. Even if Perl were to emulate fork(), you'd still be
> >     stuck, because Microsoft does not have a argc/argv-style API.

> s/use/using/;
> s/a argc/an argc/;

fixed and fixed, thanks.

If anyone knows how to excise the lame Windows comments and add
something useful, please let me know. :)

--
Posted via a free Usenet account from http://www.teranews.com

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