Chapter 11. Customized programs

90

11.3 Using pseudo ttys and modifying wtmp, utmp and lastlog

Some programs need to create pseudo ttys. This should be done using Unix98 ptys if the C

library supports it. The resulting program must not be installed setuid root, unless that is

required for other functionality.

The files

/var/run/utmp

,

/var/log/wtmp

and

/var/log/lastlog

must be installed

writable by group

utmp

. Programs which need to modify those files must be installed set 

gid

utmp

.

11.4 Editors and pagers

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 envi 

ronment 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, respec 

tively.

These two files are managed through the

dpkg

 alternatives  mechanism. Thus every package

providing an editor or pager must call the

update alternatives

script to register these

programs.

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 pro 

vided in the Debian base system 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.

2

2

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