IO::Pager(3)

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 ( FILEHANDLE FORMAT, LIST )
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.