Shell(3p) Perl Programmers Reference Guide Shell(3p)NAMEShell - run shell commands transparently within perl
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');
DESCRIPTION
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 "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. Further-
more, note that this implies that "foo" is callable by file
name only, which frequently depends on the setting of the
program's environment.
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Shell(3p) Perl Programmers Reference Guide Shell(3p)
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 set-
ting.
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.
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 "2>&1" to the command line,
so don't try this on a system not supporting this redirec-
tion.
If you set $Shell::raw to true no quoting whatsoever is
done.
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).
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;
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Shell(3p) Perl Programmers Reference Guide Shell(3p)
$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
<d.cottle@csc.canterbury.ac.nz>.
Changes for OO syntax and bug fixes by Casey West
<casey@geeknest.com>.
$Shell::raw and pod rewrite by Wolfgang Laun.
perl v5.8.8 2005-02-05 3
