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Shell(3pm)             Perl Programmers Reference Guide             Shell(3pm)

       Shell - run shell commands transparently within perl

          use Shell qw(cat ps cp);
          $passwd = cat('</etc/passwd');
          @pslines = ps('-ww'),
          cp("/etc/passwd", "/tmp/passwd");

          # object oriented
          my $sh = Shell->new;
          print $sh->ls('-l');

       This package is included as a show case, illustrating a few Perl
       features.  It shouldn't be used for production programs. Although it
       does provide a simple interface for obtaining the standard output of
       arbitrary commands, there may be better ways of achieving what you

       Running shell commands while obtaining standard output can be done with
       the "qx/STRING/" operator, or by calling "open" with a filename
       expression that ends with "|", giving you the option to process one
       line at a time.  If you don't need to process standard output at all,
       you might use "system" (in preference of doing a print with the
       collected standard output).

       Since Shell.pm and all of the aforementioned techniques use your
       system's shell to call some local command, none of them is portable
       across different systems. Note, however, that there are several built
       in functions and library packages providing portable implementations of
       functions operating on files, such as: "glob", "link" and "unlink",
       "mkdir" and "rmdir", "rename", "File::Compare", "File::Copy",
       "File::Find" etc.

       Using Shell.pm while importing "foo" creates a subroutine "foo" in the
       namespace of the importing package. Calling "foo" with arguments
       "arg1", "arg2",... results in a shell command "foo arg1 arg2...", where
       the function name and the arguments are joined with a blank. (See the
       subsection on Escaping magic characters.) Since the result is
       essentially a command line to be passed to the shell, your notion of
       arguments to the Perl function is not necessarily identical to what the
       shell treats as a command line token, to be passed as an individual
       argument to the program.  Furthermore, note that this implies that
       "foo" is callable by file name only, which frequently depends on the
       setting of the program's environment.

       Creating a Shell object gives you the opportunity to call any command
       in the usual OO notation without requiring you to announce it in the
       "use Shell" statement. Don't assume any additional semantics being
       associated with a Shell object: in no way is it similar to a shell
       process with its environment or current working directory or any other

   Escaping Magic Characters
       It is, in general, impossible to take care of quoting the shell's magic
       characters. For some obscure reason, however, Shell.pm quotes
       apostrophes ("'") and backslashes ("\") on UNIX, and spaces and quotes
       (""") on Windows.

       If you set $Shell::capture_stderr to 1, the module will attempt to
       capture the standard error output of the process as well. This is done
       by adding "2>&1" to the command line, so don't try this on a system not
       supporting this redirection.

       Setting $Shell::capture_stderr to -1 will send standard error to the
       bit bucket (i.e., the equivalent of adding "2>/dev/null" to the command
       line).  The same caveat regarding redirection applies.

       If you set $Shell::raw to true no quoting whatsoever is done.

       Quoting should be off by default.

       It isn't possible to call shell built in commands, but it can be done
       by using a workaround, e.g. shell( '-c', 'set' ).

       Capturing standard error does not work on some systems (e.g. VMS).

         Date: Thu, 22 Sep 94 16:18:16 -0700
         Message-Id: <9409222318.AA17072@scalpel.netlabs.com>
         To: perl5-porters@isu.edu
         From: Larry Wall <lwall@scalpel.netlabs.com>
         Subject: a new module I just wrote

       Here's one that'll whack your mind a little out.


           use Shell;

           $foo = echo("howdy", "<funny>", "world");
           print $foo;

           $passwd = cat("</etc/passwd");
           print $passwd;

           sub ps;
           print ps -ww;

           cp("/etc/passwd", "/etc/passwd.orig");

       That's maybe too gonzo.  It actually exports an AUTOLOAD to the current
       package (and uncovered a bug in Beta 3, by the way).  Maybe the usual
       usage should be

           use Shell qw(echo cat ps cp);

       Larry Wall

       Changes by Jenda@Krynicky.cz and Dave Cottle

       Changes for OO syntax and bug fixes by Casey West <casey@geeknest.com>.

       $Shell::raw and pod rewrite by Wolfgang Laun.

       Rewritten to use closures rather than "eval "string"" by Adriano

perl v5.12.1                      2010-05-13                        Shell(3pm)

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