linux bash shell的再次学习。

文件描述符：

stdin，stdout 和 stderr 的文件描述符分别是 0，1 和 2(一个文件描述符说白了就是文件系统为了跟踪这个打开的文件而分配给它的一个数字）

参考：https://www.cnblogs.com/sparkdev/p/10247187.html

这样子来读入文件fly的内容

 清空文件

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Reopen STDOUT and STDERR after closing them?

I am running this on an Ubuntu machine, so I am not sure if it'll work for you, but this is what I did:

$ exec 1>&0 $ exec 2>&0

Suddenly, I had STDOUT and STDERR reconnected. Magic!

Explanation: Running the following commands, we get the following output:

$ ls -l /dev/stdout lrwxrwxrwx 1 root root 15 Jun 11 23:39 /dev/stdout -> /proc/self/fd/1 $ ls -l /proc/self/fd/1 lrwx------ 1 jay jay 64 Jun 22 01:34 /proc/self/fd/1 -> /dev/pts/10 $ ls -l /proc/self/fd/ total 0 lrwx------ 1 jay jay 64 Jun 22 01:35 0 -> /dev/pts/10 lrwx------ 1 jay jay 64 Jun 22 01:35 1 -> /dev/pts/10 lrwx------ 1 jay jay 64 Jun 22 01:35 2 -> /dev/pts/10 lr-x------ 1 jay jay 64 Jun 22 01:35 3 -> /proc/12224/fd

Since all three fd's point to the same thing, we can return them back to normal just by pointing to /dev/pts/10 which the exec 1>&0 and exec 2>&0 do