NAME¶

IO::Pager - Select a pager (possibly perl-based) & pipe it text if a TTY

SYNOPSIS¶

  # Select an appropriate pager and set the PAGER environment variable
  use IO::Pager;
  # TIMTOWTDI Object-oriented
  {
    # open()                           # Use all the defaults.
    my $object = new IO::Pager;
    # open FILEHANDLE                  # Unbuffered is default subclass
    my $object = new IO::Pager *STDOUT;
    # open FILEHANDLE,EXPR             # Specify subclass
    my $object = new IO::Pager *STDOUT,  'Unbuffered';
    # Direct subclass instantiation    # FH is optional
    use IO::Pager::Unbuffered;
    my $object = new IO::Pager::Unbuffered  *STDOUT;
    $object->print("OO shiny...\n") while 1;
    print "Some other text sent to STODUT, perhaps from a foreign routine."
    # $object passes out of scope and filehandle is automagically closed
  }
  # TIMTOWTDI Procedural
  {
    # open FILEHANDLE                    # Unbuffered is default subclass
    my $token = IO::Pager::open *STDOUT;
    # open FILEHANDLE,EXPR               # Specify subclass
    my $token = IO::Pager::open *STDOUT,  'Unbuffered';
    # open FILEHANDLE,MODE,EXPR          # En lieu of a separate binmode()
    my $token = IO::Pager::open *STDOUT, '|-:utf8', 'Unbuffered';
    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(my $FH) or warn($!); XXX
    print $FH "No globs or barewords for us thanks!\n" while 1;
  }

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¶

  my $child = $token+0;

  {
     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(*STDOUT, ':LOG(clobber.log)');
    ...
    $STDOUT->binmode(':LOG(>>noclobber.log)');

    binmode(*STDOUT, ":tee(TH)");
    #OR
    $STDOUT->binmode(':tee(TH)');

  use IO::Pager::Page; #or whichever you prefer;
  ...
  eval{
    say "Producing prodigious portions of product";
    ...
  } until( eof(*STDOUT) );
  print "Cleaning up after our child before terminating."

ENVIRONMENT¶

IP_EOF

Controls IO:Pager behavior when "eof" is used.

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

IO::Pager::Perl as "tp" via IO::Pager::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. Term::Pager via IO::Pager::Perl

You may also set $ENV{PAGER} to Term::Pager to select this extensible, pure perl pager for display.

5. more

Set PAGER to "more", and cross our fingers.

Steps 1, 3 and 5 rely upon the PATH environment variable.

CAVEATS¶

You probably want to do something with SIGPIPE eg;

  eval {
    local $SIG{PIPE} = sub { die };
    local $STDOUT = IO::Pager::open(*STDOUT);
    while (1) {
      # Do something
    }
  }
  # Do something else

SEE ALSO¶

IO::Pager::Buffered, IO::Pager::Unbuffered, I::Pager::Perl, 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) 2003-2020 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.