1Shell(3)              User Contributed Perl Documentation             Shell(3)
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NAME

6       Shell - run shell commands transparently within perl
7

SYNOPSIS

9          use Shell qw(cat ps cp);
10          $passwd = cat('</etc/passwd');
11          @pslines = ps('-ww'),
12          cp("/etc/passwd", "/tmp/passwd");
13
14          # object oriented
15          my $sh = Shell->new;
16          print $sh->ls('-l');
17

DESCRIPTION

19   Caveats
20       This package is included as a show case, illustrating a few Perl
21       features.  It shouldn't be used for production programs. Although it
22       does provide a simple interface for obtaining the standard output of
23       arbitrary commands, there may be better ways of achieving what you
24       need.
25
26       Running shell commands while obtaining standard output can be done with
27       the "qx/STRING/" operator, or by calling "open" with a filename
28       expression that ends with "|", giving you the option to process one
29       line at a time.  If you don't need to process standard output at all,
30       you might use "system" (in preference of doing a print with the
31       collected standard output).
32
33       Since Shell.pm and all of the aforementioned techniques use your
34       system's shell to call some local command, none of them is portable
35       across different systems. Note, however, that there are several built
36       in functions and library packages providing portable implementations of
37       functions operating on files, such as: "glob", "link" and "unlink",
38       "mkdir" and "rmdir", "rename", "File::Compare", "File::Copy",
39       "File::Find" etc.
40
41       Using Shell.pm while importing "foo" creates a subroutine "foo" in the
42       namespace of the importing package. Calling "foo" with arguments
43       "arg1", "arg2",... results in a shell command "foo arg1 arg2...", where
44       the function name and the arguments are joined with a blank. (See the
45       subsection on Escaping magic characters.) Since the result is
46       essentially a command line to be passed to the shell, your notion of
47       arguments to the Perl function is not necessarily identical to what the
48       shell treats as a command line token, to be passed as an individual
49       argument to the program.  Furthermore, note that this implies that
50       "foo" is callable by file name only, which frequently depends on the
51       setting of the program's environment.
52
53       Creating a Shell object gives you the opportunity to call any command
54       in the usual OO notation without requiring you to announce it in the
55       "use Shell" statement. Don't assume any additional semantics being
56       associated with a Shell object: in no way is it similar to a shell
57       process with its environment or current working directory or any other
58       setting.
59
60   Escaping Magic Characters
61       It is, in general, impossible to take care of quoting the shell's magic
62       characters. For some obscure reason, however, Shell.pm quotes
63       apostrophes ("'") and backslashes ("\") on UNIX, and spaces and quotes
64       (""") on Windows.
65
66   Configuration
67       If you set $Shell::capture_stderr to 1, the module will attempt to
68       capture the standard error output of the process as well. This is done
69       by adding "2>&1" to the command line, so don't try this on a system not
70       supporting this redirection.
71
72       Setting $Shell::capture_stderr to -1 will send standard error to the
73       bit bucket (i.e., the equivalent of adding "2>/dev/null" to the command
74       line).  The same caveat regarding redirection applies.
75
76       If you set $Shell::raw to true no quoting whatsoever is done.
77

BUGS

79       Quoting should be off by default.
80
81       It isn't possible to call shell built in commands, but it can be done
82       by using a workaround, e.g. shell( '-c', 'set' ).
83
84       Capturing standard error does not work on some systems (e.g. VMS).
85

AUTHOR

87         Date: Thu, 22 Sep 94 16:18:16 -0700
88         Message-Id: <9409222318.AA17072@scalpel.netlabs.com>
89         To: perl5-porters@isu.edu
90         From: Larry Wall <lwall@scalpel.netlabs.com>
91         Subject: a new module I just wrote
92
93       Here's one that'll whack your mind a little out.
94
95           #!/usr/bin/perl
96
97           use Shell;
98
99           $foo = echo("howdy", "<funny>", "world");
100           print $foo;
101
102           $passwd = cat("</etc/passwd");
103           print $passwd;
104
105           sub ps;
106           print ps -ww;
107
108           cp("/etc/passwd", "/etc/passwd.orig");
109
110       That's maybe too gonzo.  It actually exports an AUTOLOAD to the current
111       package (and uncovered a bug in Beta 3, by the way).  Maybe the usual
112       usage should be
113
114           use Shell qw(echo cat ps cp);
115
116       Larry Wall
117
118       Changes by Jenda@Krynicky.cz and Dave Cottle
119       <d.cottle@csc.canterbury.ac.nz>.
120
121       Changes for OO syntax and bug fixes by Casey West <casey@geeknest.com>.
122
123       $Shell::raw and pod rewrite by Wolfgang Laun.
124
125       Rewritten to use closures rather than "eval "string"" by Adriano
126       Ferreira.
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129
130perl v5.30.1                      2020-01-30                          Shell(3)
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