Shell Tips

Color in Shell

Some tips to provide a more colorful shell experience.

• cat with color syntax highlighting
• Colored diff colordiff
• Color with git
• Preserve color with less
• Colors in man pages (using either less or most as pager)
• Vim-based color viewer view

cat

The example below creates a script ccat, similar to cat but with syntax highlighting (using source-highlight, ref [1]):

• Define a script ccat:

#!/bin/bash
src-hilite-lesspipe.sh $1

• The included less script is also nice. Add to your .bashrc:

export LESSOPEN="| /path/to/src-hilite-lesspipe.sh %s"
export LESS=FRX                          # At least R!

Some examples

ccat file.c
ccat file.c | less -FRX

There are some alternatives to source-highlight. For instance on Ubuntu:

• python-pygments
• code2html
• highlight
• source-highlight (a dependency of qgit)

colordiff

colordiff is a Perl wrapper around diff to show diff outputs in color:

colordiff file1 file2                     # Diff in colors
alias diff="colordiff -W ${COLUMNS:-130}" # Handy alias that also adds auto-width

Note that colordiff output can be piped through less, or colordiff can also take a diff as standard input:

colordiff file1 file2 | less -FSRX        # Page output
<patchfile colordiff                      # Colorize stdin

git

See Git (configuration section).

less

Use option -R to preserve ANSI color escape sequence in input:

colordiff file1 file2 | less -R       # As command-line option
export LESS=R                         # Better use env. var $LESS
colordiff file1 file2 | less          # ... no need to give -R anymore
export LESS=FRX                       # Even better
colordiff file1 file2 | less          # ... quit asap if less than 1-page

In git, less is called with the following option:

export lESS=FSRX                      # Default git options
                                      # ... F - quit if less than 1-page
                                      # ... S - truncate long lines
                                      # ... R - preserve color
                                      # ... X - don't initialize term (no clear)

man

To have colors in manpages, the simplest is to install the package most:

sudo apt-get install most

And then tell how you want to use it:

# SYSTEM-WIDE
sudo update-alternatives --config pager      # To select 'most' as default pager system-wide
# per USER - in ~/.bashrc
export PAGER=most                            # To select 'most' as default pager for that user
alias man="PAGER=most man"                   # To select 'most' only for manpages

However we can get the same effect with less thanks to some bash script-fu magic (see [2])

mkdir ~/.terminfo/
cd ~/.terminfo
wget http://nion.modprobe.de/mostlike.txt   # Get the new terminfo description
tic mostlike.txt                            # Compile it using terminfo entry-description compiler

Now just define the following alias in ~/.bashrc:

alias man="TERMINFO=~/.terminfo TERM=mostlike PAGER=LESS LESS=C man"     # LESS=C can be skipped or adapted

view

view is vim front-end document reader. view can highlight syntax of files based on their filename, but also based on their content (unlike source-highlight). Use view - to view standard input:

view file.c                          # Detect .c format from filename
git diff HEAD^ | view -              # Git - Will detect diff format from content
svn diff | view -                    # Svn - idem

Pager

Manpages

• By default uses pager -s
  • /usr/bin/pager is a symlink to /etc/alternatives/pager.
• Overridden by env var $PAGER.
• Overridden by env var $MANPAGER.
• Overridden by cli option -P pager.