在Linux下，有一个命令叫做which，它可以在Path中寻找某个命令所在的目录并显示出来。 Linux下：这次帅气的小编为您整理了which的用法总结（优秀2篇），在大家参照的同时，也可以分享一下给您最好的朋友。
a) 放在介词后面做介词宾语时： This is the question about which we’ve had so much discussion. 但是，如把介词放在从句的后部，这时which 就可换为that 并常省略。如上例可改为： This is the question (that) we’ve had so much discussion about.
b) 在非限制性定语从句，无论指物指人，都不能用that。指物时，只能用which 和其他关系代词。如： All the books there,which have beautiful pictures in them,were written by him.
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a)先行词为 all,everything,nothing,anything,little 等不定代词时(something 后也可用which)： Is there anything (that) I can do for you in town? That’s all (that) I know.
b) 先行词被序数词所修饰时： The first thing (that) we should do is to work out a plan.
c) 先行词被形容词最高级所修饰时： This is one of the most exciting football games (that) I have ever seen. The nanjing yangtse river bridge is the longest bridge (that) they have ever seen.
d) 先行词 被only,very,no,any,same,little,one of 等词所修饰时： This is the only thing (that) we can do now. He gave me the same pen (that) he borrowed from me. Do you have any books that were written by Lu Xun? This is the very book (that) I want to read.
e) 当先行词中既有人又有物时： The man and the car (that) you want to see are all here. 你相见的人和车都在这里。
f) that 可指人，which 则不能： Who is the man that is reading the newspaper over there?
g) 在 “the time when”等结构和某些时间状语中，when 常被that 代替，而且that 往往省略： I may leave here any time I want to. During the time I was there I visited him twice.
h)way 后面可根由that 引导的定语从句，但that 一般都省略： That was the way she looked after us.