|LESSOPEN(1)||General Commands Manual||LESSOPEN(1)|
NAME¶lessfile, lesspipe - "input preprocessor" for less.
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 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, 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
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):
*.deb, *.udeb, *.ddeb
*.gif, *.jpeg, *.jpg, *.pcd, *.png, *.tga, *.tiff, *.tif
*.iso, *.raw, *.bin
*.tar.gz, *.tgz, *.tar.z, *.tar.dz
*.gz, *.z, *.dz
*.jar, *.war, *.xpi, *.zip
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.
case "$1" in
# We don't handle this format.
# No further processing by lesspipe necessary
- Executable file that can do user defined processing. See section USER DEFINED FILTERS for more information.
BUGS¶When trying to open compressed 0 byte files, less displays the actual binary file contents. This is not a bug. less is designed to do that (see manual page less(1), section INPUT PREPROCESSOR). This is the answer of Mark Nudelman <email@example.com>:
- "I recognized when I designed it that a lesspipe
filter cannot output an empty file and have less display nothing in that
case; it's a side effect of using the "no output" case to mean
"the filter has nothing to do". It could have been designed to
have some other mechanism to indicate "nothing to do", but
"no output" seemed the simplest and most intuitive for lesspipe
if [ -z "$PS1" ]; then