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wjandrea
Asked: 2017-12-08 13:00:50 +0800 CST

How does "less" switch to the text, then back to the prompt?

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When I run less on some file, the prompt goes away, and I get the contents of the file on screen. Then when I press q, it goes back to the prompt. I think less does this by saving the current terminal buffer, opening a new buffer, outputting the file into the new one, then when closed, discarding the new buffer, and restoring the old, but I don't know what this process is called or how it does this.

I looked in man less but didn't find anything. I tried googling it, but couldn't find anything useful, except that the screen command can do the same thing with shell sessions.

Ultimately, I'm asking because I want git diff to use a new buffer instead of printing inline. I've already set GIT_PAGER=less and git --paginate diff, but they didn't change anything. And I have a workaround, but it's a bit long: git diff --color=always | less -R

Update: After some research, it looks like tput smcup and tput rmcup are high-level commands to do the same thing, probably using the termcap package.

command-line

1 Answers

  1. Best Answer

    All of less’s screen management functions are in its screen.c module. At startup, unless it’s in “no init” (-X or --no-init) mode, it outputs its sc_init string, which is termcap’s ti string (“terminal initialisation”, which gets the terminal ready for full-screen, cursor-controlling operation). At exit, it outputs its sc_deinit string, which is termcap’s te string.

    The behaviour you’re seeing is the default behaviour with git, if less isn’t configured (i.e. the LESS variable is unset); when that’s the case, git runs less with the FRX options, which cause less to respectively quit if the content fits on a single screen, display colours, and skip initialising the terminal.

    To get the behaviour you’re after, set LESS to -R, or set the core.pager git setting to something like less -+X (see man git-config for details).

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