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 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 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, 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: <>
     From: Larry Wall <>
     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 and Dave Cottle

   Changes for OO syntax and bug fixes by Casey West <>.

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

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


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