Re: Random string generation during *-install

[Taylor R Campbell <campbell+netbsd-tech-pkg%mumble.net@localhost>]

   Date: Mon, 25 May 2015 01:31:01 +0200
   From: Jean-Yves Migeon <jeanyves.migeon%free.fr@localhost>

   Le 24/05/2015 20:47, Kamil Rytarowski a écrit :
   > Once I had to do something similar in a shell script and replace bash(1)
   > $RANDOM with a portable alternative.
   >
   > I went for awk(1), initial ideas are at http://awk.info/?tip/random

Beware that most programming languages' built-in random number
generators are lousy, and totally unfit for applications requiring
unpredictability.  E.g., if your application is a network daemon
requiring an unpredictable secret random seed, you cannot use awk's
rand safely to generate it.

   Thanks. I ended up using urandom and tr(1) and delete any non printable 
   char, not quite perfect but does an ok job.

That's what I would recommend.

(tr -cd '[:graph:]' | head -c 20) < /dev/urandom

There's a slim chance that on some exotic Unixoid platform pkgsrc
supports, you can't assume there will be a /dev/urandom.  But I
wouldn't worry about it until someone actually trips over it.

   >> What is the correct way of generating a fixed random string on
   >> pre-install or do-install stage?
   [...]
   BTW is there a way to add arbitrary commands to a pkginstall's INSTALL 
   script? Just wondering whether binary packages would add even more 
   restrictions to the environment (not needed in my present scenario, but 
   alas, sooner or later...)

Don't use pre-install and do-install for this -- use the INSTALL
script alongside the Makefile.  The pre-install and do-install make
targets are always (unless you explicitly set USE_DESTDIR=no, which is
ill-advised) run at build-time when installing into a destdir before
creating a package, not at install-time when you actually install the
package.