NAME¶
IO::Pager - Select a pager and pipe text to it if destination is a TTY
SYNOPSIS¶
# Select an appropriate pager and set the PAGER environment variable
use IO::Pager;
# Optionally, pipe output to it
{
# TIMTOWTDI, not an exhaustive list but you can infer the others
my $token = IO::Pager::open *STDOUT; # Unbuffered is default subclass
my $token = new IO::Pager *STDOUT, 'Unbuffered'; # Specify subclass
my $token = IO::Pager::Unbuffered::open *STDOUT; # Must 'use' class!
my $token = new IO::Pager::Unbuffered *STDOUT; # Must 'use' class!
print <<" HEREDOC" ;
...
A bunch of text later
HEREDOC
# $token passes out of scope and filehandle is automagically closed
}
{
# You can also use scalar filehandles...
my $token = IO::Pager::open($FH) or warn($!);
print $FH "No globs or barewords for us thanks!\n";
}
{
# ...or an object interface
my $token = new IO::Pager::Buffered;
$token->print("OO shiny...\n");
}
DESCRIPTION¶
IO::Pager can be used to locate an available pager and set the
PAGER
environment variable (see "NOTES"). It is also a factory for
creating I/O objects such as IO::Pager::Buffered and IO::Pager::Unbuffered.
IO::Pager subclasses are designed to programmatically decide whether or not to
pipe a filehandle's output to a program specified in
PAGER. Subclasses
may implement only the IO handle methods desired and inherit the remainder of
those outlined below from IO::Pager. For anything else, YMMV. See the
appropriate subclass for implementation specific details.
METHODS¶
new( [FILEHANDLE], [SUBCLASS] )¶
Almost identical to open, except that you will get an IO::Handle back if there's
no TTY to allow for IO::Pager agnostic programming.
open( [FILEHANDLE], [SUBCLASS] )¶
Instantiate a new IO::Pager, which will paginate output sent to FILEHANDLE if
interacting with a TTY.
Save the return value to check for errors, use as an object, or for implict
close of OO handles when the variable passes out of scope.
- FILEHANDLE
- You may provide a glob or scalar.
Defaults to currently select()-ed FILEHANDLE.
- SUBCLASS
- Specifies which variety of IO::Pager to create. This accepts fully
qualified packages IO::Pager::Buffered, or simply the third portion
of the package name Buffered for brevity.
Defaults to IO::Pager::Unbuffered.
Returns false and sets $! on failure, same as perl's
"open".
PID¶
Call this method on the token returned by "open" to get the process
identifier for the child process i.e; pager; if you need to perform some long
term process management e.g; perl's "waitpid"
You can also access the PID by numifying the instantiation token like so:
my $child = $token+0;
close( FILEHANDLE )¶
Explicitly close the filehandle, this stops any redirection of output on
FILEHANDLE that may have been warranted.
This does not default to the current filehandle.
Alternatively, you may rely upon the implicit close of lexical handles as they
pass out of scope e.g;
{
IO::Pager::open local *RIBBIT;
print RIBBIT "No toad sexing allowed";
...
}
#The filehandle is closed to additional output
{
my $token = new IO::Pager::Buffered;
$token->print("I like trains");
...
}
#The string "I like trains" is flushed to the pager, and the handle closed
binmode( FILEHANDLE )¶
Used to set the I/O layer a.k.a. discipline of a filehandle, such as ':utf8' for
UTF-8 encoding.
print ( FILEHANDLE LIST )¶
print() to the filehandle.
printf() to the filehandle.
syswrite( FILEHANDLE, SCALAR, [LENGTH], [OFFSET] )¶
syswrite() to the filehandle.
ENVIRONMENT¶
- PAGER
- The location of the default pager.
- PATH
- If the location in PAGER is not absolute, PATH may be searched.
See "NOTES" for more information.
FILES¶
IO::Pager may fall back to these binaries in order if
PAGER is not
executable.
- /etc/alternatives/pager
- /usr/local/bin/less
- /usr/bin/less
- /usr/bin/more
See "NOTES" for more information.
NOTES¶
The algorithm for determining which pager to use is as follows:
- 1. Defer to PAGER
- If the PAGER environment variable is set, use the pager it
identifies, unless this pager is not available.
- 2. Usual suspects
- Try the standard, hardcoded paths in "FILES".
- 3. File::Which
- If File::Which is available, use the first pager possible amongst
"less", "most", "w3m", "lv",
"pg" and more.
- 4. more
- Set PAGER to "more", and cross our fingers.
Steps 1, 3 and 4 rely upon the
PATH environment variable.
SEE ALSO¶
IO::Pager::Buffered, IO::Pager::Unbuffered, IO::Pager::Page,
IO::Page, Meta::Tool::Less
AUTHOR¶
Jerrad Pierce <jpierce@cpan.org>
Florent Angly <florent.angly@gmail.com>
This module was inspired by Monte Mitzelfelt's IO::Page 0.02
COPYRIGHT AND LICENSE¶
Copyright (C) 2003-2012 Jerrad Pierce
- •
- Thou shalt not claim ownership of unmodified materials.
- •
- Thou shalt not claim whole ownership of modified materials.
- •
- Thou shalt grant the indemnity of the provider of materials.
- •
- Thou shalt use and dispense freely without other restrictions.
Or, if you prefer:
This library is free software; you can redistribute it and/or modify it under
the same terms as Perl itself, either Perl version 5.0 or, at your option, any
later version of Perl 5 you may have available.