Re: Bug#363250: general: Custom PAGER gives error on sid, but works on sarge

[Loïc Minier <lool+debian@via.ecp.fr>]

On Sat, Apr 22, 2006, Manoj Srivastava wrote:
> > #363250 is more about documenting the semantics of $PAGER (whether
> > it can uses sh syntax, or whether it's a command with parameters
> > separated with spaces), to be documented in man man, and/or policy.
>         Err, we should define how it behaves, not what is inside
>  it. As long as one can pipe things to $PAGER or use $PAGER on a file,
>  what it contains should not matter.

 Please read again the original report, the submitter wanted to have a
 pipe of commands in $PAGER, he said this worked in the past, and works
 on other distros.  He did not want to simply be able to use $PAGER on a
 file or to pipe stuff to $PAGER, he wanted $PAGER to be parsed as a
 pipeline, as in sh syntax.

>         The safe bet would be for $PAGER to be a script or executable
>  which can handle reading from file or STDIN, like proper UNIX
>  programs.

 This is an independent problem  First, we already have one layer of sh
 scripting with the sensible-pager program, and it would be a good
 enough place to handle the cases you mention, would people and programs
 use sensible-pager as the default pager.  Second, this doesn't define
 what should happen when someone redefines $PAGER: what if one user
 wants $PAGER to be a pipeline?

>         To make life easier for people writing programs which deal
>  with $PAGER, and  are using the POSIX exce* set of calls, one may
>  constrain $PAGER to "path [arg [arg ..]]", with no pipes or other
>  shell meta-characters.

 Yes, I think this is safe, but I'd go even further and propose the
 following:
 A/ handling of pager in programs
 1/ programs should default to sensible-pager
 2/ programs should offer a way to override the default pager in some
    way, for example via an environment variable called <program>_PAGER,
    or a configuration setting -- it might even be better for them to
    avoid handling $PAGER, see 1/

 B/ user configuration of the pager
 When defined, $PAGER is a sh pipeline which reads its data from stdin.


 This is with the intent of moving any logic for deciding of the best
 pager to run out of each individual program requiring a pager, exactly
 as in the sensible-browser case, which can consider $BROWSER, $DISPLAY,
 x-www-browser, and www-browser to find a sensible browser.

 Manoj, how would this fit in policy?

-- 
Loïc Minier <lool@dooz.org>
"You can gtk_main_run, but you can't gtk_widget_hide." --danw, 19-jul-04