LESSOPEN(1)						      General Commands Manual						       LESSOPEN(1)

NAME

       lessfile, lesspipe - "input preprocessor" for  less.

SYNOPSIS

       lessfile, lesspipe

DESCRIPTION

       This manual page documents briefly the lessfile, and lesspipe commands.	This manual page was written for the Debian GNU/Linux distribution
       because the input preprocessor scripts are provided by Debian GNU/Linux and are not part of the original program.

       lessfile and lesspipe are programs that can be used to modify the way the contents of a file are displayed in less.   What  this  means	is
       that less can automatically open up tar files, uncompress gzipped files, and even display something reasonable for graphics files.

       lesspipe  will  toss  the contents/info on STDOUT and less will read them as they come across.  This means that you do not have to wait for
       the decoding to finish before less shows you the file.  This also means that you will get a 'byte N' instead of an N% as  your  file  posi-
       tion.  You can seek to the end and back to get the N% but that means you have to wait for the pipe to finish.

       lessfile  will  toss  the contents/info on a file which less will then read.  After you are done, lessfile will then delete the file.  This
       means that the process has to finish before you see it, but you get nice percentages (N%) up front.

USAGE

       Just put one of the following two commands in your login script (e.g.  ~/.bash_profile):

	 eval "$(lessfile)"

       or

	 eval "$(lesspipe)"

FILE TYPE RECOGNITION

       File types are recognized by their extensions.  This is a list of currently supported extensions  (grouped  by  the  programs  that  handle
       them):

	 *.a
	 *.arj
	 *.tar.bz2
	 *.bz
	 *.bz2
	 *.deb, *.udeb, *.ddeb
	 *.doc
	 *.gif, *.jpeg, *.jpg, *.pcd, *.png, *.tga, *.tiff, *.tif
	 *.iso, *.raw, *.bin
	 *.lha, *.lzh
	 *.tar.lz, *.tlz
	 *.lz
	 *.7z
	 *.pdf
	 *.rar, *.r[0-9][0-9]
	 *.rpm
	 *.tar.gz, *.tgz, *.tar.z, *.tar.dz
	 *.gz, *.z, *.dz
	 *.tar
	 *.tar.xz, *.xz
	 *.jar, *.war, *.xpi, *.zip
	 *.zoo

USER DEFINED FILTERS

       It  is  possible  to extend and overwrite the default lesspipe and lessfile input processor if you have specialized requirements. Create an
       executable program with the name .lessfilter and put it into your home directory. This can be a shell script or a binary program.

       It is important that this program returns the correct exit code: return 0 if your filter handles  the  input,  return  1  if  the  standard
       lesspipe/lessfile filter should handle the input.

       Here is an example script:

	 #!/bin/sh

	 case "$1" in
	     *.extension)
		 extension-handler "$1"
		 ;;
	     *)
		 # We don't handle this format.
		 exit 1
	 esac

	 # No further processing by lesspipe necessary
	 exit 0

FILES

       ~/.lessfilter
	      Executable file that can do user defined processing. See section USER DEFINED FILTERS for more information.

BUGS

       When trying to open compressed 0 byte files, less displays the actual binary file contents. This is not a bug.  less is designed to do that
       (see manual page less(1), section INPUT PREPROCESSOR).  This is the answer of Mark Nudelman <markn@greenwoodsoftware.com>:

	      "I recognized when I designed it that a lesspipe filter cannot output an empty file and have less display nothing in that case; it's
	      a  side effect of using the "no output" case to mean "the filter has nothing to do".  It could have been designed to have some other
	      mechanism to indicate "nothing to do", but "no output" seemed the simplest and most intuitive for lesspipe writers."

       Sometimes, less does not display the contents file you want to view but output that  is	produced  by  your  login  scripts  (~/.bashrc	or
       ~/.bash_profile). This happens because less uses your current shell to run the lesspipe filter. Bash first looks for the variable $BASH_ENV
       in the environment expands its value and  uses the expanded value as the name of a file to read and execute. If this file produces any out-
       put less will display this. A way to solve this problem is to put the following lines on the top of your login script that produces output:

	 if [ -z "$PS1" ]; then
	     exit
	 fi

       This tests whether the prompt variable $PS1 is set and if it isn't (which is the case for non-interactive shells) it will exit the script.

SEE ALSO

       less(1)

AUTHOR

       This  manual  page was written by Thomas Schoepf <schoepf@debian.org>, for the Debian GNU/Linux system (but may be used by others). Most of
       the text was copied from a description written by Darren Stalder <torin@daft.com>.

																       LESSOPEN(1)