1 whereis ：显示指令的二进制程序、源代码文件和man手册的路径
查找所有信息
~$ whereis emacsemacs: /usr/bin/emacs /etc/emacs /usr/lib/emacs /usr/bin/X11/emacs /usr/share/emacs /usr/share/man/man1/emacs.1.gz
仅查找二进制程序
~$ whereis -b emacsemacs: /usr/bin/emacs /etc/emacs /usr/lib/emacs /usr/bin/X11/emacs /usr/share/emacs
仅查找源代码文件
~$ whereis -s emacsemacs:
仅查找man手册页
~$ whereis -m emacsemacs: /usr/share/man/man1/emacs.1.gz
2 which : 仅显示指令的绝对路径
和whereis不同的是，which只能显示指令的绝对路径。
~$ which emacs/usr/bin/emacs
3 locate/slocate ：快速定位文件的路径
locate指令利用事先建立的系统中左右文件名称及路径的数据库，从而实现快速定位。如果该数据库比较陈旧，使用updatedb即可更新。和whereis以及which相比，，locate可以查找普通文件，只要是带有搜索关键字的都会输出，因此内容会比较多。
输出符合条件的文件总数
~$ locate -c emacs3737
输出所有匹配条目
~$ 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
因为在路上你就已经收获了自由自在的好心情。
