请问/dev/null有什么作用啊？

Phaedo

RT

晨想

。吃掉所有给她的东西。。。。。不吐出来。。。

一般就是作用于把无用的结果都导向那里去。

Phaedo

:confused: :confused: 不大明白！

Hauser

Let's say you have a file called 'messages' which was created like this:

$ ls -lhF | tee messages

Now you don't want to keep the content of the file but you do want to keep the file itself for later use, you may open the file with an editor, select all and delete; another way to do this is to give the following cat command to truncate the file to zero length while preserving the ownership and permissions of the file:

$ cat /dev/null > messages

Phaedo

这样说就明白点的了，那个tee是什么东西？

benu

举个例子来说吧。不知道你在普通用户下执行过find命令没有。
试试这两条命令的输出就知道了：

$find /  -name kernel.h
$find / -name kernel.h  2>/dev/null

2>/dev/null  的意思就是将命令的错误输出通通扔到/dev/null这个无底洞里去

benu

? 我的帖子的时间怎么没对

benu

呵呵，我一直的理解 /dev/null是用来扔东西的，没想到还可以这样用，又学到了，

Hauser

最初由 Phaedo 发表
那个tee是什么东西？

The tee utility copies standard input to standard ouput and to one or more files you specify on the command line.  Without any options, tee overwrites the output files if they exist, creates the ouput files if they don't exist.  To avoid overwriting existing files you may use the append option:
$  ls -lhF / | tee -a ~/tmp/messages ~/ls-root

Phaedo

谢谢各位的指点！:thank