1 whereis ：顯示指令的二進制程序、源代碼文件和man手冊的路徑
查找所有信息
~$ whereis emacs
emacs: /usr/bin/emacs /etc/emacs
/usr/lib/emacs /usr/bin/X11/emacs
/usr/share/emacs /usr/share/man/man1/emacs.1.gz
僅查找二進制程序
~$ whereis -b emacs
emacs: /usr/bin/emacs /etc/emacs
/usr/lib/emacs /usr/bin/X11/emacs /usr/share/emacs
僅查找源代碼文件
~$ whereis -s emacs
emacs:
僅查找man手冊頁
~$ whereis -m emacs
emacs: /usr/share/man/man1/emacs.1.gz
2 which : 僅顯示指令的絕對路徑
和whereis不同的是，which只能顯示指令的絕對路徑。
~$ which emacs
/usr/bin/emacs
3 locate/slocate ：快速定位文件的路徑
locate指令利用事先建立的系統中左右文件名稱及路徑的數據庫，從而實現快速定位。如果該數據庫比較陳舊，使用updatedb即可更新。和whereis以及which相比，locate可以查找普通文件，只要是帶有搜索關鍵字的都會輸出，因此內容會比較多。
輸出符合條件的文件總數
~$ locate -c emacs
3737
輸出所有匹配條目
~$ locate emacs
/usr/share/emacs23/site-lisp/flim/mmgeneric.elc
/usr/share/emacs23/site-lisp/flim/ntlm.el
/usr/share/emacs23/site-lisp/flim/ntlm.elc
/usr/share/emacs23/site-lisp/flim/qmtp.el
/usr/share/emacs23/site-lisp/flim/qmtp.elc
/usr/share/emacs23/site-lisp/flim/sasl-cram.el
/usr/share/emacs23/site-lisp/flim/sasl-cram.elc
/usr/share/emacs23/site-lisp/flim/sasl-digest.el
/usr/share/emacs23/site-lisp/flim/sasl-digest.elc
/usr/share/emacs23/site-lisp/flim/sasl-ntlm.el
/usr/share/emacs23/site-lisp/flim/sasl-ntlm.elc
/usr/share/emacs23/site-lisp/flim/sasl-scram.el
/usr/share/emacs23/site-lisp/flim/sasl-scram.elc
/usr/share/emacs23/site-lisp/flim/sasl.el
/usr/share/emacs23/site-lisp/flim/sasl.elc
/usr/share/emacs23/site-lisp/flim/sha1-dl.el
/usr/share/emacs23/site-lisp/flim/sha1-dl.elc
/usr/share/emacs23/site-lisp/flim/sha1-el.el
/usr/share/emacs23/site-lisp/flim/sha1-el.elc
/usr/share/emacs23/site-lisp/flim/sha1.el
/usr/share/emacs23/site-lisp/flim/sha1.elc
/usr/share/emacs23/site-lisp/w3m/shimbun/sb-atmarkit.el
/usr/share/emacs23/site-lisp/w3m/shimbun/sb-atmarkit.elc
........
/var/lib/dpkg/info/emacsen-common.list
/var/lib/dpkg/info/emacsen-common.postinst
/var/lib/dpkg/info/emacsen-common.postrm
/var/lib/dpkg/info/emacsen-common.prerm
/var/lib/emacsen-common/installed-flavors
