Manual: lessfile

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 dis‐
       played 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 position.	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, less‐
       file 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
	 *.egg
	 *.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
	 *.whl
	 *.jar, *.war, *.xpi, *.zip
	 *.zoo
	 *.tar.zst, *.tzst
	 *.zst

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
       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	pro‐
       duces any output 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-inter‐
       active shells) it will exit the script.

SEE ALSO
       less(1)

AUTHOR
       This manual page was written by Thomas Schoepf , 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
       .

												 LESSOPEN(1)