[Nix-dev] less: When assumptions ruin the world

Alexander Kjeldaas ak at formalprivacy.com
Sun Jan 4 02:24:57 CET 2015

Just a note for those who are annoyed that less will clear the screen on

export LESS=-X

On Fri, Jan 2, 2015 at 4:30 PM, Ertugrul Söylemez <ertesx at gmx.de> wrote:

> Hi Eelco,
> >> There is a very good reason for this principle.  If a program does
> >> more than what it's intended to do, then it hurts composability.
> >
> > There shouldn't be an issue with composability here, because Nix will
> > only run the pager when stdout is a terminal. So things work fine if
> > you pipe Nix into another command.
> Let me give you an example where this assumption fails:  Listing the
> current generations from your shell profile.  In fact something very
> similar happened to me, which motivated me to start this thread:  The
> change broke my assumption that Nix can be used safely from a shell
> script.
> Nothing bad happened, but one day was wasted, because a script stopped
> for `less` without my knowledge.
> I really believe that projects should start as non-interactive script-
> and command-line-friendly programs /by default/.  I'd go as far as to
> call this a good design principle.  Frontends can always be made.
> Greets,
> Ertugrul
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