Find which , where is software or library installed in (Ubuntu)Linux

Find which , where is software or library installed in (Ubuntu)Linux

Example

$which gcc

$whereis gcc

$locate signal.h

Locate searches the periodic index which is made by cron

/usr/include/signal.h

Find which version of rpm is installed for Redhat or Centos

$rpm -q python

python-2.4.3-21.el5

Find which version of deb is installed

Ubuntu

dpkg