Shell.

Quoting.

http://www.mpi-inf.mpg.de/~uwe/lehre/unixffb/quoting-guide.html

A Guide to Unix Shell Quoting

Portability.

http://code.dogmap.org/lintsh/

lintsh is a Bourne shell that optionally warns about suspicious or nonportable constructs

http://www.gnu.org/software/autoconf/manual/html_node/Portable-Shell.html

Portable Shell Programming

Kill processes after timeout.

$ yes xxx& p1=$! ; yes ===& p2=$! ; sleep 2; kill $p1; kill $p2