search installed application

Red Hat/Fedora Core/CentOS Linux

Type the following command to get list of all installed software
# rpm -qa | less

Debian Linux

Type the following command to get list of all installed software:
# dpkg --get-selections

Ubuntu Linux

Type the following command to get list of all installed software:
# sudo dpkg --get-selections

FreeBSD

Type the following command to get list of all installed software:
# pkg_info | less
# pkg_info apache

Use pkg_version command to summarizes the versions of all installed packages:
# pkg_version | less
# pkg_version | grep 'lsof'

OpenBSD

OpenBSD also use pkg_info command to display list of all installed packages or software:
# pkg_info | less
# pkg_info apache