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Accepted
Socob
Asked: 2019-07-09 08:35:35 +0800 CST

Different behavior of unset vs. empty LESS environment variable?

  • 772

I wanted to change the default behavior of the less command, so I added the following to ~/.profile:

LESS="$LESS -x4"
export LESS

However, the mere presence of a set LESS environment variable seems to change the behavior of the less command, since this now causes git diff to show me raw escape sequences.

More generally, the output of

LESS='' git diff

and

unset LESS; git diff

differs. What is the difference between having LESS unset and LESS set to an empty value (besides the former apparently implying -R)?

command-line environment-variables git less

2 Answers

  1. Best Answer

    This has nothing to do with less, and everything to do with git. Quoting from the git-config(1) manpage (emphasis mine):

    When the LESS environment variable is unset, Git sets it to FRX (if LESS environment variable is set, Git does not change it at all).

    The R option of less is that which controls whether it interprets colors escapes and such, and which is NOT on by default, but is only set by git if the LESS environment variable was unset.

    • 6

  2. $LESS is an environment variable used by less. From man less: 

    Options are also taken from the environment variable "LESS".  For example, to avoid typing
   "less -options ..." each time less is invoked, you might tell csh:

   setenv LESS "-options"

   or if you use sh:

   LESS="-options"; export LESS

    You should use some other environment variable name.

    • -3