Colors in grep

To turn on colors in grep, you may add --color=auto to the GREP_OPTIONS environment variable. The way to do it is of course shell-dependant. E.g. add the following to your shell rc file:

export GREP_OPTIONS='--color=auto'

ls colors

add an alias to your shell rc file:

alias ls "ls --color=auto"

GIT_PAGER and LESS colors

I was wondering why, working on two different machines, I was able to display git-log and git-diff colors on one machine and not on the other, despite the same git configuration file ~/.gitconfig:

[color]
diff    = auto
status  = auto
branch  = auto
log     = auto

and no particular settings regarding colors in <repository>/.git/config

Although I was not using a Mac, the solution was in this blog post: that is, setting the GIT_PAGER variable to cat was already solving the problem; GIT_PAGER sets which program should be used by git to display for example the diff and log output (default less).

The actual problem was in less and how it outputs ANSI color ESC codes. A solution, similarly to what suggested in that post, was to set the LESS variable to -R and leave GIT_PAGER unset, as it originally was. Regarding the other options suggested in the blog post for LESS, -X and -e have no influence on color display, and -R is probably better than -r; in particular, this in an extract of the less manual, at the -r/-R section, explaining why:

-r or --raw-control-chars

Causes  "raw"  control  characters  to be displayed.
[...] Warning: when the -r option is used, less cannot
keep track of the actual appearance of the screen
(since this depends on how the screen responds to
each type of control character). Thus, various display
problems may result, such as long lines being split
in the wrong place.

-R or --RAW-CONTROL-CHARS

Like -r, but only ANSI "color" escape sequences are
output in "raw" form. Unlike -r, the screen appearance
is maintained correctly in most cases.  [...]

Turn colors on in vi/vim

If the color syntax highlighting is off, you can turn it on by editing (or creating) ~/.vimrc, adding the following line:

:syn on