.so macro in man pages

[Joseph Koshy]

> like to know why the latter method didn't work for me as expected, just
> for the reference.

man -d will report the exact command line used to generate the manual
page.

   $ man -d -M /tmp/man bar 
   trying command: (cd /tmp/man ; /usr/bin/zcat /tmp/man/man1/bar.1.gz
| /usr/bin/tbl | /usr/bin/groff -S -Wall -mtty-char -man -Tascii |
/usr/bin/col | /usr/bin/less)

  $ gzip -dc man1/bar.1.gz
  .so man2/foo.2

However the man2/ directory only contains the gzipped version of the manual
page.  Consequently the .so include by groff will fail.

  $ man -M /tmp/man bar
  <standard input>:1: can't open `man2/foo.2': No such file or directory