perl-IO-Interactive

This module provides three utility subroutines that make it easier to
develop interactive applications.
The 'ARGV' filehandle, the one that '<>' or an empty 'readline()' uses, has
various magic associated with it. It's not actually opened until you try to
read from it. Checking '-t ARGV' before you've tried to read from it might
give you the wrong answer. Not only that, you might not read from 'ARGV'.
If the value in '@ARGV' is the magic filename '-' (a convention to mean the
standard filehandle for input or output), 'ARGV' might actually be 'STDIN'.
You don't want to think about all of this. This module is discussed in
Perl Best Practices on page 218. Also see the 'ARGV' entry in perlvar and
the 'readline' entry in perlfunc.

'is_interactive()'

This subroutine returns true if 'ARGV' and the currently selected
filehandle (usually 'STDOUT') are connected to the terminal. The test is
considerably more sophisticated than:
-t *ARGV &amp;&amp; -t *STDOUT


as it takes into account the magic behaviour of '*ARGV'.
You can also pass 'is_interactive' a writable filehandle, in which case it
requires that filehandle be connected to a terminal (instead of the
currently selected). The usual suspect here is '*STDERR':
if ( is_interactive(*STDERR) ) {
    carp $warning;
}



'interactive()'

This subroutine returns '*STDOUT' if 'is_interactive' is true. If
'is_interactive()' is false, 'interactive' returns a filehandle that does
not print.
This makes it easy to create applications that print out only when the
application is interactive:
print {interactive} "Please enter a value: ";
my $value = &lt;&gt;;


You can also pass 'interactive' a writable filehandle, in which case it
writes to that filehandle if it is connected to a terminal (instead of
writing to 'STDOUT'). Once again, the usual suspect is 'STDERR':
print {interactive(*STDERR)} $warning;



'busy {...}'

This subroutine takes a block as its single argument and executes that
block. Whilst the block is executed, 'ARGV' is temporarily replaced by a
closed filehandle. That is, no input from 'ARGV' is possible in a 'busy'
block. Furthermore, any attempts to send input into the 'busy' block
through 'ARGV' is intercepted and a warning message is printed to
'STDERR'. The 'busy' call returns a filehandle that contains the
intercepted input.
A 'busy' block is therefore useful to prevent attempts at input when the
program is busy at some non-interactive task.

          

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License: Artistic-2.0
URL: https://metacpan.org/release/IO-Interactive