在Debian系的Linux中检查软件包是否被安装的方法

  dpkg -s firefox

  Package: firefox
  Status: install ok installed
  Priority: optional
  Section: web
  Installed-Size: 93339
  Maintainer: Ubuntu Mozilla Team <ubuntu-mozillateam@lists.ubuntu.com>
  Architecture: amd64
  Version: 35.0+build3-0ubuntu0.14.04.2
  Replaces: kubuntu-firefox-installer
  Provides: gnome-www-browser, iceweasel, www-browser
  Depends: lsb-release, libasound2 (>= 1.0.16), libatk1.0-0 (>= 1.12.4), libc6 (>= 2.17), libcairo2 (>= 1.2.4), libdbus-1-3 (>= 1.0.2), libdbus-glib-1-2 (>= 0.78), libfontconfig1 (>= 2.9.0), libfreetype6 (>= 2.2.1), libgcc1 (>= 1:4.1.1), libgdk-pixbuf2.0-0 (>= 2.22.0), libglib2.0-0 (>= 2.37.3), libgtk2.0-0 (>= 2.24.0), libpango-1.0-0 (>= 1.22.0), libpangocairo-1.0-0 (>= 1.14.0), libstartup-notification0 (>= 0.8), libstdc++6 (>= 4.6), libx11-6, libxcomposite1 (>= 1:0.3-1), libxdamage1 (>= 1:1.1), libxext6, libxfixes3, libxrender1, libxt6
  Recommends: xul-ext-ubufox, libcanberra0, libdbusmenu-glib4, libdbusmenu-gtk4
  Suggests: ttf-lyx
  Conffiles:
  /etc/firefox/syspref.js 09e457e65435a1a043521f2bd19cd2a1
  /etc/apport/blacklist.d/firefox ee63264f847e671832d42255912ce144
  /etc/apport/native-origins.d/firefox 7c26b75c7c2b715c89cc6d85338252a4
  /etc/apparmor.d/usr.bin.firefox f54f7a43361c7ecfa3874abca2f292cf
  Description: Safe and easy web browser from Mozilla
  Firefox delivers safe, easy web browsing. A familiar user interface,
  enhanced security features including protection from online identity theft,
  and integrated search let you get the most out of the web.
  Xul-Appid: {ec8030f7-c20a-464f-9b0e-13a3a9e97384}

  dpkg-query -l firefox

  Desired=Unknown/Install/Remove/Purge/Hold
  | Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
  |/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
  ||/ Name Version Architecture Description
  +++-====================================-=======================-=======================-=============================================================================
  ii firefox 35.0+build3-0ubuntu0.14 amd64 Safe and easy web browser from Mozilla

  dpkg --get-selections

  abiword install
  abiword-common install
  accountsservice install
  acl install
  adduser install
  alsa-base install
  alsa-utils install
  anacron install
  app-install-data install
  apparmor install
  .
  .
  .
  zeitgeist install
  zeitgeist-core install
  zeitgeist-datahub install
  zenity install
  zenity-common install
  zip install
  zlib1g:amd64 install
  zlib1g:i386 install

  dpkg --get-selections | grep gcc

  gcc install
  gcc-4.8 install
  gcc-4.8-base:amd64 install
  gcc-4.8-base:i386 install
  gcc-4.9-base:amd64 install
  gcc-4.9-base:i386 install
  libgcc-4.8-dev:amd64 install
  libgcc1:amd64 install
  libgcc1:i386 install

dpkg -L gcc-4.8

  /.
  /usr
  /usr/share
  /usr/share/doc
  /usr/share/doc/gcc-4.8-base
  /usr/share/doc/gcc-4.8-base/README.Bugs
  /usr/share/doc/gcc-4.8-base/NEWS.html
  /usr/share/doc/gcc-4.8-base/quadmath
  /usr/share/doc/gcc-4.8-base/quadmath/changelog.gz
  /usr/share/doc/gcc-4.8-base/gcc
  .
  .
  .
  /usr/bin/x86_64-linux-gnu-gcc-4.8
  /usr/bin/x86_64-linux-gnu-gcc-ar-4.8
  /usr/bin/x86_64-linux-gnu-gcov-4.8