How to syntax highlight via Less

Question

is there a way to syntax highlight a file I see in Less?

actually I'm using this command to open an xml file (and sometimes a series of them)

less htmleditors/htmleditors_config.xml

or

less [multiple files]

I'd like to stay in Less (to learn that program better and to use my knowledge of :n and :p for next/previous navigation)

But it also want some kind of basic syntax highlighting – at least show the comments differently. Do you know any way to do it?

Answer 1

You can use GNU's source-highlight, as shown here (path may differ, see below):

 export LESSOPEN="| /usr/bin/src-hilite-lesspipe.sh %s"
 export LESS=' -R '

As of Debian Stretch and Fedora 25, package names and script paths differ

• Debian:

  sudo apt install libsource-highlight-common source-highlight
  dpkg -L libsource-highlight-common | grep lesspipe
  # /usr/share/source-highlight/src-hilite-lesspipe.sh
  

• Fedora:

  sudo dnf install source-highlight
  rpm -ql source-highlight | grep lesspipe
  # /usr/bin/source-highlight/src-hilite-lesspipe.sh
  

Answer 2

Best of both previous answers: you can invoke system default editor from within less, by pressing v.

Answer 3

pygmentize somefile.ex | less -R

or

function cless () {
    pygmentize -f terminal "$1" | less -R
}

Pygmentize comes as a part of the Pygments Python syntax highliter.

Answer 4

As others have said, you can use the power of vim. But importantly, you can do so without learning how to use vi/vim.

Vim comes with a less.vim script that works pretty well as a replacement for less, with full color syntax highlighting. It uses less keybindings (just hit 'q' to quit).

It had a few problems, so I improved it. Here's a screenshot from my blog post on it (archived 2013-04-09; original throws 503):

Answer 5

I think that you should use a text editor. I like vim myself. That will give you LOTS of power when viewing files and then when you want to edit them you will already know the basics.

Here are some of the advantages of using a text editor (specifically vim):

• syntax-highlighting
• powerful movement commands
• find
• jump to specific location in a file (called a mark)
• folding (useful when you just want to see function stubbs)

To open your file in readonly mode use this:

vim -R <file name>

Here is a basic navigation guide:

j - move down one line
k - move up one line
h - left one char
l -right one char

ctrl-f - forward one page
ctrl-b - back one page

/<something> - search for something
n - next of whatever you searched for
N - next (search backwards) of whatever you searched for

:q - quit
:q! - quit without saving
:w - save

Here is a link for more information:

http://www.viemu.com/a_vi_vim_graphical_cheat_sheet_tutorial.html

Just to recap, if you will use unix vim is pretty fundamental. I have heard that learning vim is like learning to type. It is the next most useful tool you can learn for programming.

(Just to avoid editor wars you could also look into emacs or another editor, however I personally prefer vim)

Answer 6

I was also searching for this and found another solution using Vim: http://ubuntu-tutorials.com/2008/07/14/use-vim-as-a-syntax-highlighting-pager/

The post is rather old, so now on more recent distros vim 7.2 is shipped and the .bashrc will read: alias vless='vim -u /usr/share/vim/vim72/macros/less.vim'

Answer 7

I'm glad to announce a new package, e2ansi, that provides syntax highlighting support for pagers like more and less.

The package use the mother of all text editors, Emacs, to perform the actual syntax highlighting. As an added bonus, all other conversions normally performed by Emacs -- like uncompressing files -- is also performed.

Example

The following is the result of viewing a file using less and e2ansi:

Configuration

The package provides a command-line tool e2ansi-cat that starts Emacs in batch mode, opens files, syntax highlight them, and renders the result using ANSI sequences.

You can integrate this into less by setting the following variables to, for example (the location of your init file may vary):

export "LESSOPEN=||-/usr/local/emacs --batch -Q -l ~/.emacs -l bin/e2ansi-cat %s"
export "LESS=-r"
alias "more=less -X -E"

In the configuration above, less restores the original terminal window content whereas more simply output new content after the prompt.

Note: If you use an old version of less, it might not support the || or the - syntax, in which case you may need to use simply LESSOPEN=|/usr/local/emacs ....

Using less in pipes

The "-" character in LESSOPEN indicates that the input filter should also be used when piping text into less. In this case, Emacs can only rely on text itself (and not a file name). Fortunately, Emacs provides a system for this. In addition, the provided file file e2ansi-magic.el sets up additional file types. For example:

Why use Emacs?

• Emacs has support for virtually all programming languages and structured text formats. In most cases, the syntax highlighting support is excellent.
• You can easily add support for more languages and formats, or modify existing packages to suit you needs.
• Emacs support color themes. When using e2ansi, the colors in the theme is preserved when viewing a file in less. You can pick a suitable color theme from a number of sources, or design your own.
• If you use Emacs as your editor of choice, you will get the same highlighting in the editor as you get when viewing a file using less (minus limitations in ANSI sequence format and the terminal window).
• less will take advantage of Emacs features that perform automatic conversion, for example uncompressing files. In fact, you can teach Emacs to perform any kind of conversion like automatically convert a binary file to human readable form using an external tool.
• You can view files located on other machines by using Emacs' syntax for remote access like /USER@HOST:FILENAME.

Useful links

• e2ansi is distributed on Melpa and can be installed using the standard Emacs package system
• e2ansi is hosted on GitHub
• The e2ansi page on the Emacs Wiki
• The home of less.

Operating system notes

• On MS Windows, the console does not natively support ANSI sequences. Fortunately, the less application is capable of rendering them. I am not aware of any contemporary binary distribution of less for MS Windows and the provided build files is hard to use. Fortunately, it's easy to build less using CMake, see this text for details.

• OS X distributes an ancient version of less. Fortunately, it's easy to build a modern version directly from the source.

Answer 8

If you have GNU Source-highlight installed you can use the following command to highlight the syntax of a single file:

$ src-hilite-lesspipe.sh yourfile.xml | less -R

Answer 9

After installing GNU's source-highlight (package dev-util/source-highlight on sabayon/gentoo), I configured those envs in /etc/bash/bashrc.d/my-less-src-highlight:

#default:    export LESSOPEN="|lesspipe %s"
#don't like: export LESSOPEN="| /usr/bin/src-hilite-lesspipe.sh %s"
#default:    export LESS=" -R -M --shift 5"
export LESSCOLOR=always
export LESSCOLORIZER=/usr/bin/src-hilite-lesspipe.sh

I did not like to replace lesspipe because that has other features. Concatenation did not work.

Answer 10

I found highlight which:

• Supports multiple colour schemes and 256-colours
• Works on STDIN (unlike source-highlight)
• Is much faster than pygmentize

Here is a script I call highlight-less-wrapper which includes .bashrc instructions on how to setup less to use it automatically.

#!/bin/bash

# Have highlight read from STDIN if '-' is given as filename

# Setup - Add to .bashrc:
# LESSOPEN='|-highlight-less-wrapper "%s"'
# export LESS=-FMRXis

# Usage:
# $ less file
# OR
# $ pipeline | less

warn () { printf "%s: %s\n" "$(basename "$0")" "$*" 1>&2; }
die () { warn "$@"; exit 1; }

# Argument checking
case $# in
    0)
        # Allow `exec $0` for less setup
        echo "LESSOPEN='|-$(readlink -f "$0") "'"%s"'\'
        exit 255 ;;
    1)
        # Only one argument is expected.
        # less will invoke multiple times given multiple files.
        file=$1
        if [[ $file != - && ! -r $file ]]; then  # less passes '-' for STDIN
            die "Cannot open $file for reading"
        fi ;;
    *)
        die "Expected only one argument" ;;
esac

# Run highlight
# highlight will read from STDIN when given a null filename
run_highlight () {
    highlight --force -O truecolor --style aiseered "$1"
}

if [[ $file == - ]]; then  # Run on stdin
    run_highlight ""
else
    run_highlight "$file"
fi

Answer 11

source-highlight has a .sh script located in /usr/share/source-highlight/*.sh. I've created a symbolic link to it with name hcat in /usr/bin.

It shows highlighted output in terminal (console) – hcat is highlighted cat.

How to:

[me@this]<bash><~> 43 
21:23 Fri Apr 19 > sudo apt-get install source-highlight

[me@this]<bash><~> 28 
21:03 Fri Apr 19 > ll /usr/share/source-highlight/*.sh
-rwxr-xr-x 1 root root 432 May  1  2012 /usr/share/source-highlight/src-hilite-lesspipe.sh*

[me@this]<bash><~> 29 
21:04 Fri Apr 19 > sudo su
root@this:/home/me# cd /usr/bin/
root@this:/usr/bin# ln -s /usr/share/source-highlight/src-hilite-lesspipe.sh hcat

[me@this]<bash><~> 36 
21:07 Fri Apr 19 > hcat test.xml

Answer 12

Using OS X 10.9 (Maverick) this would do the trick:

• brew install source-highlight (Assuming brew is installed - http://brew.sh)

• sudo nano /etc/launchd.conf

  setenv LESSOPEN="| /usr/local/bin/src-hilite-lesspipe.sh %s"     
  setenv LESS=' -R '
  

  (Add to /etc/launchd.conf)

• reboot

Answer 13

If you want the same syntax highlighting you use in Vim, but for some reason you prefer to use less as your pager, you can use this script: https://github.com/rkitover/vimpager

The basic usage would be:

vimpager file.txt

or

vimcat file.ext | less -R

You can use -c to pass extra commands which aren't in your .vimrc (e.g. selecting a different colorscheme). The full command I use is:

vimcat -c 'set cmdheight=20' -c 'hi! clear Normal' -o - "$FILENAME" | less -REXS

Beware: If your Vim asks you to press Enter when it starts up, you won't see the prompt, but nothing will happen until you press Enter! The cmdheight trick above can help to mitigate that.

Answer 14

I had the same question and I landed hear, read all answers and the following is what I finally did to have syntax highlighting everytime I use less or most:

sudo apt install source-highlight

Then I went and created an alias for my less and most (I use ZSH, but you can add aliases for your .bashrc file if you use bash):

vim ~/.zshrc

(For those who might get stuck in vim: press i to go to edit mode, when you are done press Esc then : then x and finally Enter to save the changes)

And paste the following lines for debian-based distros (like Debian, Ubuntu, Mint, etc.):

alias most='AliasFuncLess() { unset -f AliasFuncLess; $(dpkg -L libsource-highlight-common | grep lesspipe) "$1" | less -R };AliasFuncLess'
alias most='AliasFuncMost() { unset -f AliasFuncMost; $(dpkg -L libsource-highlight-common | grep lesspipe) "$1" | most };AliasFuncMost'

or for RPM distros (Redhat, Fedora, Centos):

alias most='AliasFuncLess() { unset -f AliasFuncLess; $(rpm -ql source-highlight | grep lesspipe) "$1" | less -R };AliasFuncLess'
alias most='AliasFuncMost() { unset -f AliasFuncMost; $(rpm -ql source-highlight | grep lesspipe) "$1" | most };AliasFuncMost'

Remember to close the terminal and open it again to make sure alias is created.

Now you can enjoy the colors:

most yourFile.xml

Answer 15

With https://gitlab.com/saalen/highlight or app-text/highlight on Gentoo already installed, configuration below seems to work simple and beautiful:

$ env | grep LESS      
LESS=-R -M --shift 5           
LESSOPEN=| command highlight -O ansi %s

Answer 16

In mac, you can just type view filename, does similar thing like less.

Answer 17

There is a fish shell plugin to help integration. However, you still need to install the lib (see brandstaetter answer)

fisher install decors/fish-source-highlight