1IO::Interactive(3) User Contributed Perl Documentation IO::Interactive(3)
2
6 IO::Interactive - Utilities for interactive I/O
7
9 This document describes IO::Interactive version 1.02
10
12 use IO::Interactive qw(is_interactive interactive busy);
13 if ( is_interactive() ) {
15 print "Running interactively\n";
16 }
17 # or...
19 print {interactive} "Running interactively\n";
21 $fh = busy {
24 do_noninteractive_stuff();
25 }
26
28 This module provides three utility subroutines that make it easier to
29 develop interactive applications.
30 The "ARGV" filehandle, the one that "<>" or an empty "readline()" uses,
32 has various magic associated with it. It's not actually opened until
33 you try to read from it. Checking "-t ARGV" before you've tried to read
34 from it might give you the wrong answer. Not only that, you might not
35 read from "ARGV". If the value in @ARGV is the magic filename "-" (a
36 convention to mean the standard filehandle for input or output), "ARGV"
37 might actually be "STDIN". You don't want to think about all of this.
38 This module is discussed in Perl Best Practices on page 218. Also see
39 the "ARGV" entry in perlvar and the "readline" entry in perlfunc.
40 "is_interactive()"
42 This subroutine returns true if *ARGV and the currently selected
43 filehandle (usually *STDOUT) are connected to the terminal. The
44 test is considerably more sophisticated than:
45 -t *ARGV && -t *STDOUT
47 as it takes into account the magic behaviour of *ARGV.
49 You can also pass "is_interactive" a writable filehandle, in which
51 case it requires that filehandle be connected to a terminal
52 (instead of the currently selected). The usual suspect here is
53 *STDERR:
54 if ( is_interactive(*STDERR) ) {
56 carp $warning;
57 }
58 "interactive()"
60 This subroutine returns *STDOUT if "is_interactive" is true. If
61 "is_interactive()" is false, "interactive" returns a filehandle
62 that does not print.
63 This makes it easy to create applications that print out only when
65 the application is interactive:
66 print {interactive} "Please enter a value: ";
68 my $value = <>;
69 You can also pass "interactive" a writable filehandle, in which
71 case it writes to that filehandle if it is connected to a terminal
72 (instead of writing to *STDOUT). Once again, the usual suspect is
73 *STDERR:
74 print {interactive(*STDERR)} $warning;
76 "busy {...}"
78 This subroutine takes a block as its single argument and executes
79 that block. Whilst the block is executed, *ARGV is temporarily
80 replaced by a closed filehandle. That is, no input from *ARGV is
81 possible in a "busy" block. Furthermore, any attempts to send
82 input into the "busy" block through *ARGV is intercepted and a
83 warning message is printed to *STDERR. The "busy" call returns a
84 filehandle that contains the intercepted input.
85 A "busy" block is therefore useful to prevent attempts at input
87 when the program is busy at some non-interactive task.
88
90 Unknown subroutine (%s) requested
91 This module only exports the three subroutines described above.
92 You asked for something else. Maybe you misspelled the subroutine
93 you wanted.
94
96 IO::Interactive requires no configuration files or environment
97 variables.
98
100 This module requires the "openhandle()" subroutine from the
101 Scalar::Util module.
102
104 None reported.
105
107 No bugs have been reported.
108 Please report any bugs or feature requests to Github
110 <https://github.com/briandfoy/io-interactive/issues>.
111
113 This code is in GitHub:
114 https://github.com/briandfoy/io-interactive
116
118 Damian Conway "<DCONWAY@cpan.org>"
119 Currently maintained by brian d foy "<bdfoy@cpan.org>".
121 1.01 patch DMUEY "dmuey@cpan.org"
123
125 Copyright © 2005-2021, Damian Conway "<DCONWAY@cpan.org>". All rights
126 reserved.
127 This module is free software; you can redistribute it and/or modify it
129 under the same terms as Perl itself.
130
132 BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
133 FOR THE SOFTWARE, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT
134 WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER
135 PARTIES PROVIDE THE SOFTWARE "AS IS" WITHOUT WARRANTY OF ANY KIND,
136 EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
137 WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
138 ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE SOFTWARE IS WITH
139 YOU. SHOULD THE SOFTWARE PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL
140 NECESSARY SERVICING, REPAIR, OR CORRECTION.
141 IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
143 WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
144 REDISTRIBUTE THE SOFTWARE AS PERMITTED BY THE ABOVE LICENCE, BE LIABLE
145 TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL, OR
146 CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE
147 SOFTWARE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING
148 RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A
149 FAILURE OF THE SOFTWARE TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF
150 SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
151 DAMAGES.
152perl v5.34.0 2022-01-21 IO::Interactive(3)