locate  [-ir]  keywords

-i:表示忽略大小写
-r:表示后面跟正则表达式

下面来看看例子：

[root@localhost shell]# locate apache
/etc/selinux/targeted/modules/active/modules/apache.pp
/usr/lib/python2.7/site-packages/sos/plugins/apache.py
/usr/lib/python2.7/site-packages/sos/plugins/apache.pyc
/usr/lib/python2.7/site-packages/sos/plugins/apache.pyo
/usr/share/openscap/schemas/oval/5.10/apache-definitions-schema.xsd
/usr/share/openscap/schemas/oval/5.10/apache-system-characteristics-schema.xsd
/usr/share/openscap/schemas/oval/5.10.1/apache-definitions-schema.xsd
/usr/share/openscap/schemas/oval/5.10.1/apache-system-characteristics-schema.xsd
/usr/share/openscap/schemas/oval/5.11/apache-definitions-schema.xsd
/usr/share/openscap/schemas/oval/5.11/apache-system-characteristics-schema.xsd
/usr/share/openscap/schemas/oval/5.3/apache-definitions-schema.xsd
/usr/share/openscap/schemas/oval/5.3/apache-system-characteristics-schema.xsd

[root@localhost shell]# locate -i  apache
/etc/selinux/targeted/modules/active/modules/apache.pp
/usr/lib/python2.7/site-packages/sos/plugins/apache.py
/usr/lib/python2.7/site-packages/sos/plugins/apache.pyc
/usr/lib/python2.7/site-packages/sos/plugins/apache.pyo
/usr/share/doc/clucene-core-2.3.3.4/APACHE.license
/usr/share/doc/python-cryptography-0.8.2/LICENSE.APACHE
/usr/share/doc/wqy-microhei-fonts-0.2.0/LICENSE_Apache2.txt
/usr/share/openscap/schemas/oval/5.10/apache-definitions-schema.xsd
/usr/share/openscap/schemas/oval/5.10/apache-system-characteristics-schema.xsd
/usr/share/openscap/schemas/oval/5.10.1/apache-definitions-schema.xsd
/usr/share/openscap/schemas/oval/5.10.1/apache-system-characteristics-schema.xsd

由上面的例子可以看出默认和加-i参数的区别。
locate命令查找速度很快，但是有限制的，因为locate查找的数据是由已创建的数据库/var/lib/mlocate/里面的数据查找得到的，不用从硬盘上去访问数据，所以他的查找速度很快。
但是不准确，因为数据库的创建默认是每天执行一次(不同的Linux distrution是不同的)，所以你刚刚安装的软件是查不到的，有办法解决这个问题，就是手动更新数据库即可，直接执行updatedb命令即可，更新的时候时间可能会很长。

最后总结一下：
locate：是依据/var/lib/mlocate/数据库中的信息来查找数据的
updatedb：是根据/etc/update.conf的设置去查找硬盘中的文件名，并跟新/var/lib/mlocate内的信息