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+.TH LESSOPEN 1
+.\" NAME should be all caps, SECTION should be 1-8, maybe w/ subsection
+.\" other parms are allowed: see man(7), man(1)
+.SH NAME
+lessfile, lesspipe \- "input preprocessor" for  less.
+.SH SYNOPSIS
+.B lessfile, lesspipe
+.SH "DESCRIPTION"
+This manual page documents briefly the
+.IR lessfile ,
+and
+.I 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.
+.PP
+.I lessfile
+and
+.I lesspipe
+are programs that can be used to modify the way the contents of a file are
+displayed in
+.I less.
+What this means is that
+.I less
+can automatically open
+up tar files, uncompress gzipped files, and even display something reasonable
+for graphics files.
+.PP
+.I lesspipe
+will toss the contents/info on STDOUT and
+.I 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.
+.PP
+.I lessfile
+will toss the contents/info on a file which
+.I less
+will then
+read.  After you are done,
+.I 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.
+.
+.SH USAGE
+Just put one of the following two commands in your login script (e.g.
+~/.bash_profile):
+.PP
+  eval "$(lessfile)"
+.PP
+or
+.PP
+  eval "$(lesspipe)"
+.SH 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):
+
+.DS
+  *.a
+  *.arj
+  *.tar.bz2
+  *.bz
+  *.bz2
+  *.deb, *.udeb
+  *.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
+.DE
+.SH USER DEFINED FILTERS
+It is possible to extend and overwrite the default
+.I lesspipe
+and
+.I lessfile
+input processor if you have specialized requirements. Create an executable
+program with the name
+.I .lessfilter
+and put it into your home directory. This can be a shell script or a binary
+program.
+
+.PP
+It is important that this program returns the correct exit code: return 0 if
+your filter handles the input, return 1 if the standard
+.I lesspipe/lessfile
+filter should handle the input.
+
+.PP
+Here is an example script:
+
+.DS
+  #!/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
+.DE
+
+.SH FILES
+.TP
+.I ~/.lessfilter
+Executable file that can do user defined processing. See section USER DEFINED
+FILTERS for more information.
+.SH BUGS
+When trying to open compressed 0 byte files,
+.I less
+displays the actual binary file contents. This is not a bug.
+.I less
+is designed to do that (see manual page less(1), section INPUT PREPROCESSOR).
+This is the answer of Mark Nudelman <markn@greenwoodsoftware.com>:
+.IP
+"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."
+
+.PP
+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 $BASH_ENV in the environment expands its value
+and  uses the expanded value as the name of a file to read and execute. If
+this file produces any output less will display this. A way to solve this
+problem is to put the following lines on the top of your login script that
+produces output:
+
+.DS
+  if [ -z "$PS1" ]; then
+      exit
+  fi
+.DE
+
+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.
+.SH "SEE ALSO"
+less(1)
+.SH 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>.