(debian-policy.info)Editors and pagers

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11.4 Editors and pagers
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Some programs have the ability to launch an editor or pager program to
edit or display a text document.  Since there are lots of different
editors and pagers available in the Debian distribution, the system
administrator and each user should have the possibility to choose their
preferred editor and pager.

In addition, every program should choose a good default editor/pager if
none is selected by the user or system administrator.

Thus, every program that launches an editor or pager must use the EDITOR
or PAGER environment variable to determine the editor or pager the user
wishes to use.  If these variables are not set, the programs
‘/usr/bin/editor’ and ‘/usr/bin/pager’ should be used, respectively.
These commands may be invoked explicitly (e.g., as ‘/usr/bin/editor’) or
via a PATH search (e.g., as ‘editor’).

These two files are managed through the ‘dpkg’ “alternatives” mechanism.
Every package providing an editor or pager must call the
‘update-alternatives’ script to register as an alternative for
‘/usr/bin/editor’ or ‘/usr/bin/pager’ as appropriate.  The alternative
should have a slave alternative for ‘/usr/share/man/man1/editor.1.gz’ or
‘/usr/share/man/man1/pager.1.gz’ pointing to the corresponding manual
page.

If it is very hard to adapt a program to make use of the EDITOR or PAGER
variables, that program may be configured to use
‘/usr/bin/sensible-editor’ and ‘/usr/bin/sensible-pager’ as the editor
or pager program respectively.  These are two scripts provided in the
sensible-utils package that check the EDITOR and PAGER variables and
launch the appropriate program, and fall back to ‘/usr/bin/editor’ and
‘/usr/bin/pager’ if the variable is not set.

A program may also use the VISUAL environment variable to determine the
user’s choice of editor.  If it exists, it should take precedence over
EDITOR. This is in fact what ‘/usr/bin/sensible-editor’ does.

It is not required for a package to depend on ‘editor’ and ‘pager’, nor
is it required for a package to provide such virtual packages.  (1)

   ---------- Footnotes ----------

   (1) The Debian base system already provides an editor and a pager
program.