Hi Étienne!
Thanks for your comprehensive explanation. I appreciate it very much. Feb 12, 2019, 1:38 AM by etienne.moll...@mailoo.org: > Tom Bachreier, on 2019-02-11: > >> BUT wait... >> >> I was wondering why do we have man-db.timer in the first place? >> > > On my Sid machine, this file is known under the name of > /usr/lib/systemd/system/man-db.service and has, among other > things, these lines: > Just for the record: On testing I found the file in /lib/systemd/system instead. > > # Expunge old catman pages which have not been read in a week. > ExecStart=/usr/bin/find /var/cache/man -type f -name *.gz -atime +6 -delete > # Regenerate man database. > ExecStart=/usr/bin/mandb --quiet > > Seems there is not only a mandb re-indexing, but also some > cleanup is done apparently, given the `find [...] -delete`. > [Re-indexing for man, whatis and apropos] In my opinion still the perfect job for a postinstall-script. Manpages doesn't change other than during install, update or remove of packages. > > The other mechanism consists in caching the binary > representation of compiled manual pages. > [...] > You can try for yourself how `man` handles the research inside > your documentation by passing the debug option -d and browsing > the output debug.out at your convenience: > > $ man -d man 2> debug.out > > I discovered for instance that I never use this cache because I > cap my terminal width to 65 characters using the variable > MANWIDTH, and the debug output shown me: > > Terminal width 65 not within cat page range [80, 80] > Same here. But I tried a 80 columns terminal, too and no cache files were generated either. I don't care but it is strange. I do not even have catx-directories - not in /usr/share/man/ or /var/cache/man/. The debug shows in this case: > found ultimate source file /usr/share/man/man1/man.1.gz > converted /usr/share/man/man1/man.1.gz to /usr/share/man/cat1/man.1.gz > is_changed: a=/usr/share/man/man1/man.1.gz, b=/usr/share/man/cat1/man.1.gz > (-2) > converted /var/cache/man/cat1/man.1.gz to /var/cache/man/cat1/man.1.gz > will try cat file /var/cache/man/cat1/man.1.gz [...] > is_changed: a=/usr/share/man/man1/man.1.gz, b=/var/cache/man/cat1/man.1.gz > (-2) > cat dir /var/cache/man/cat1 does not exist I would translate this to: It tried but failed to generate the cache file. > Since lots of people do not use 80 char width terminals anymore, > mostly because of "maximize window", I get this function is not > of much use lately, at least not by using Debian default value. > That thing can be configured in /etc/manpath.config if you are > interested in such manipulations. > In /etc/manpath.config I found one can disable caching completely - nice. > NOCACHE > > Well, I don't believe this catman mechanism is of much use > today, most manual pages are rendered in the blink of an eye. > Last time I had to /wait/ more than a seconds for a manual page > to be formatted, that was on a Sun Fire V440. > I agree, for myself it is pretty useless. I never missed it. > > To summarize, the patched service does a clear the cache of > unused raw man pages, which should not be referenced anymore by > mandb. Part of all this is more or less described in the manual > pages man(1), most particularly in sections "OVERVIEW" and > "DEFAULTS", which have a succinct descriptions of the various > mechanisms involved. See also catman(8) and mandb(8). > > To summarize for myself. The timer/service doesn't do anything valuable for me so I will disable it. Étienne, thanks again for your time! It helped me to understand if the timer is needed on my computers or not. Tom
