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[PATCH] Shell.pm: pod rewrite and new mini-feature $Shell::raw

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From:
LAUN Wolfgang
Date:
May 31, 2004 22:54
Subject:
[PATCH] Shell.pm: pod rewrite and new mini-feature $Shell::raw
Message ID:
DF27CDCBD2581D4B88431901094E4B4D02B0C744@attmsx1.aut.alcatel.at
Most of this patch is a rewrite of the pod, but there is one small
addition thrown in: It's now possible, by setting $Shell::raw to
true, to inhibit all escaping of magic characters. This (I think)
is the only way to cope with the hydra-like argument about what
should be quoted and what not.

I didn't add that this package might be omitted from some future
release.

For better reading, I'm including the rewritten pod section.

Regards
Wolfgang


=head1 NAME

Shell - run shell commands transparently within perl

=head1 SYNOPSIS

   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');

=head1 DESCRIPTION

=head2 Caveats

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 need.

Running shell commands while obtaining standard output can be done with the
C<qx/STRING/> operator, or by calling C<open> with a filename expression that
ends with C<|>, 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 C<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: C<glob>, C<link> and C<unlink>, C<mkdir> and C<rmdir>, 
C<rename>, C<File::Compare>, C<File::Copy>, C<File::Find> etc.

Using Shell.pm while importing C<foo> creates a subroutine C<foo> in the
namespace of the importing package. Calling C<foo> with arguments C<arg1>,
C<arg2>,... results in a shell command C<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 C<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
C<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 setting.

=head2 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 (C<'>) and backslashes (C<\>) on UNIX, and spaces and
quotes (C<">) on Windows.

=head2 Configuration

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

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

=head1 BUGS

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).

=head1 AUTHOR

  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.

    #!/usr/bin/perl

    use Shell;

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

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

    sub ps;
    print ps -ww;

    cp("/etc/passwd", "/tmp/passwd");

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 <d.cottle@csc.canterbury.ac.nz>.

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

C<$Shell::raw> and pod rewrite by Wolfgang Laun.



--- lib/Shell.pm.old	Sun May 23 13:55:13 2004
+++ lib/Shell.pm	Mon May 31 18:44:32 2004
@@ -2,9 +2,9 @@
 use 5.006_001;
 use strict;
 use warnings;
-our($capture_stderr, $VERSION, $AUTOLOAD);
+our($capture_stderr, $raw, $VERSION, $AUTOLOAD);
 
-$VERSION = '0.5';
+$VERSION = '0.6';
 
 sub new { bless \my $foo, shift }
 sub DESTROY { }
@@ -62,7 +62,8 @@
 	    } else {
 		my \$a;
 		my \@arr = \@_;
-		if ('$^O' eq 'MSWin32') {
+                unless( \$Shell::raw ){
+                  if ('$^O' eq 'MSWin32') {
 		    # XXX this special-casing should not be needed
 		    # if we do quoting right on Windows. :-(
 		    #
@@ -78,11 +79,12 @@
 			s/\\\\\\\\"/\\\\\\\\"""/g;
 			\$_ = qq["\$_"] if /\\s/;
 		    }
-		} else {
+		  } else {
 		    for (\@arr) {
 			s/(['\\\\])/\\\\\$1/g;
 			\$_ = \$_;
-		    }
+ 		    }
+                  }
 		}
 		push \@arr, '2>&1' if \$Shell::capture_stderr;
 		open(SUBPROC, join(' ', '$cmd', \@arr, '|'))
@@ -115,10 +117,82 @@
 
 =head1 SYNOPSIS
 
-See below.
+   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');
 
 =head1 DESCRIPTION
 
+=head2 Caveats
+
+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 need.
+
+Running shell commands while obtaining standard output can be done with the
+C<qx/STRING/> operator, or by calling C<open> with a filename expression that
+ends with C<|>, 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 C<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: C<glob>, C<link> and C<unlink>, C<mkdir> and C<rmdir>, 
+C<rename>, C<File::Compare>, C<File::Copy>, C<File::Find> etc.
+
+Using Shell.pm while importing C<foo> creates a subroutine C<foo> in the
+namespace of the importing package. Calling C<foo> with arguments C<arg1>,
+C<arg2>,... results in a shell command C<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 C<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
+C<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 setting.
+
+=head2 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 (C<'>) and backslashes (C<\>) on UNIX, and spaces and
+quotes (C<">) on Windows.
+
+=head2 Configuration
+
+If you set $Shell::capture_stderr to true, the module will attempt to
+capture the standard error output of the process as well. This is
+done by adding C<2E<gt>&1> to the command line, so don't try this on
+a system not supporting this redirection.
+
+If you set $Shell::raw to true no quoting whatsoever is done.
+
+=head1 BUGS
+
+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).
+
+=head1 AUTHOR
+
   Date: Thu, 22 Sep 94 16:18:16 -0700
   Message-Id: <9409222318.AA17072@scalpel.netlabs.com>
   To: perl5-porters@isu.edu
@@ -148,55 +222,12 @@
 
     use Shell qw(echo cat ps cp);
 
-Larry
-
-
-If you set $Shell::capture_stderr to 1, the module will attempt to
-capture the STDERR of the process as well.
-
-The module now should work on Win32.
-
- Jenda
-
-There seemed to be a problem where all arguments to a shell command were
-quoted before being executed.  As in the following example:
-
- cat('</etc/passwd');
- ls('*.pl');
-
-really turned into:
-
- cat '</etc/passwd'
- ls '*.pl'
-
-instead of:
-
-  cat </etc/passwd
-  ls *.pl
-
-and of course, this is wrong.
-
-I have fixed this bug, it was brought up by Wolfgang Laun [ID 20000326.008]
-
-Casey
-
-=head2 OBJECT ORIENTED SYNTAX
-
-Shell now has an OO interface.  Good for namespace conservation 
-and shell representation.
-
- use Shell;
- my $sh = Shell->new;
- print $sh->ls;
-
-Casey
-
-=head1 AUTHOR
-
 Larry Wall
 
-Changes by Jenda@Krynicky.cz and Dave Cottle <d.cottle@csc.canterbury.ac.nz>
+Changes by Jenda@Krynicky.cz and Dave Cottle <d.cottle@csc.canterbury.ac.nz>.
+
+Changes for OO syntax and bug fixes by Casey West <casey@geeknest.com>.
 
-Changes and bug fixes by Casey West <casey@geeknest.com>
+C<$Shell::raw> and pod rewrite by Wolfgang Laun.
 
 =cut

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