Where are the commands available in the man page window documented, and are these commands system-dependent?

It is indeed right in the manual page for man, under the "Controlling formatted output" subheading and repeated later on in the "ENVIRONMENT" section for good measure:

By default, man uses pager -s.
The manual page explains how there is a hierarchy of environment variables and command-line options (PAGER, MANPAGER, and --pager) for overriding the default.

This is how it reads on systems such as Debian Linux. On systems such as Oracle Linux, in contrast, the man-db package has been built with a different default, which is however still reflected right there in the manual page in the same places:

By default, man uses less -s.

The man-db package attempts to auto-detect, at compile time, which default pager to build-in to the command, and document in its manual page, out of less, more, and pager.

On systems such as Debian Linux, the pager command is part of the "alternatives" system and can map to one of several actual commands:

jdebp % update-alternatives --list pager
/bin/less
/bin/more
/usr/bin/pg
/usr/bin/w3m
jdebp %

So one consults their respective manual pages for how to drive them from the keyboard, according to which alternative has been chosen. Usefully, the Debian alternatives system keeps the manual page in synch with the chosen command, so reading this manual page is quite straightforward:

man pager


Man uses a pager to show the content.

The exact details depend on which version of man you are using.

For the version used on many systems:

  • If the option -p pager is given then that pager is used.
  • Otherwise if the environment variable MANPAGER is set it is used.
  • Otherwise if PAGER is set it is used.
  • Otherwise the default is to use /usr/bin/less

If the manual page is in HTML format then BROWSER is used instead of MANPAGER/PAGER

Debian uses man-db which has different defaults.

Read man man for the details


Thanks to @Rastapopoulos, I find a line related to less in man man on a old Linux box (man version: 1.6f) in the ENVIRONMENT section that states,

BROWSER The name of a browser to use for displaying HTML manual pages. If it is not set, /usr/bin/less is used.

However on a newer box (man version: 2.6.3) this line has been replaced by

BROWSER If $BROWSER is set, its value is a colon-delimited list of commands, each of which in turn is used to try to start a web browser for man --html. In each command, %s is replaced by a file? name containing the HTML output from groff, %% is replaced by a single percent sign (%), and %c is replaced by a colon (:).

Based on these information I believe it is formatted in less by default (at least for the first case). However, even if this is the case, it is documented in a way that doesn't seem clear to me (or I have learnt the man command the wrong way).

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