GNU extensions to Unix commands (was: All caps .TH page title)

[Alejandro Colomar (man-pages)]

Hi Ralph,

On 7/23/22 12:36, Ralph Corderoy wrote:
> Hi Alejandro,
>
> Wandering off-topic...
>
> > $ find man* -type f \
> >     | tr '[:upper:]' '[:lower:]' \
> >     | sort \
> >     | uniq -d \
> >     | while read f; do
> >         find man* -type f \
> >         | grep -i $f;
> >     done;
> > man2/_Exit.2
> > man2/_exit.2
> > man3/nan.3
> > man3/NAN.3
>
> You may like to know GNU's uniq(1) has ‘-D’ to print all duplicates
> and ‘-i’ to ignore case.
>
>      $ find -type f | sort -f | uniq -Di
>      ./man2/_exit.2
>      ./man2/_Exit.2
>      ./man3/nan.3
>      ./man3/NAN.3
>      ./man3/sd_bus_error_map.3
>      ./man3/SD_BUS_ERROR_MAP.3
>      ./man8/pam.8
>      ./man8/PAM.8
>      $

Hmm, interesting options.

> > $ find man* -type f \
> >     | tr '[:upper:]' '[:lower:]' \
> >     | sort \
> >     | uniq -d \
> >     | while read f; do
> >         find man* -type f \
> >         | grep -i $f;
> >     done \
> >     | while read f; do
> >         echo ===$f===;
> >         head -n1 $f;
> >     done;
>
> GNU's grep(1) has ‘-m’ for the maximum number of matches.

Interesting use of grep(1) to combine printf(1) and head(1) too.

>      $ grep -m1 ^ `find -type f | sort -f | uniq -Di`

I'm a big fan of pipes and xargs(1).  I only use `` or $() when I 
_really_ need to.  I'd use:

$ find -type f | sort -f | uniq -Di | xargs grep -m1 ^

This more clearly shows the processing done step by step.
It also has the benefit of not being limited to ARG_MAX.

>      ./man2/_exit.2:.\" This manpage is Copyright (C) 1992 Drew Eckhardt;
>      ./man2/_Exit.2:.so man2/_exit.2
>      ./man3/nan.3:.\" Copyright 2002 Walter Harms 
> (walter.harms@informatik.uni-oldenburg.de)
>      ./man3/NAN.3:.so man3/INFINITY.3
>      ./man3/sd_bus_error_map.3:.so sd_bus_error_add_map.3
>      ./man3/SD_BUS_ERROR_MAP.3:.so sd_bus_error_add_map.3
>      ./man8/pam.8:.so PAM.8
>      ./man8/PAM.8:'\" t
>      $

Cheers,

Alex

--
Alejandro Colomar
Linux man-pages comaintainer; http://www.kernel.org/doc/man-pages/
http://www.alejandro-colomar.es/