通过尾巴和头通过管道三通的文件 [英] Piping a file through tail and head via tee

问题描述

从<起始href=\"http://stackoverflow.com/questions/8624669/unix-head-and-tail-of-file/16637719?noredirect=1#comment23935309_16637719\">here我试图读取文件，并发射头和文件的尾部（读取文件仅一次）。

Starting from here I tried to read a file and emit the head and the tail of the file (reading the file only once).

我试过如下：
T恤＆GT;（头）＆GT;（尾）＆GT;的/ dev / null的＆LT;的text.txt

该行正常工作，但我想摆脱在/ dev / null的的。所以我尝试：
T恤＆GT;（头）|尾LT;的text.txt

This line works as expected, but I'd like to get rid of the /dev/null. So I tried: tee >(head) | tail < text.txt

但正如预期的（当然，如我所料），这条线是不行的，它打印头，但之后没有返回。显然，尾巴在等待着什么。但我不知道什么确切。
我发现这个 SO质疑，但我无法得到它与运行给出答案。

But this line does not work as expected (well, as I expected), it prints the head but does not return after that. Apparently tail is waiting for something. But I don't know what for exactly. I found this SO question, but I could not get it running with the given answers.

推荐答案

在 T恤＆GT;（头）|尾LT;的text.txt ，文本文件直接到尾。你可能意味着

In tee >(head) | tail < text.txt, the text file goes directly to tail. You probably meant

tee >(head) < text.txt | tail

这不会等待任何事情，但也不管用，因为这两个发球和头部的输出去的尾巴。

Which does not wait for anything, but does not work either, because the output of both tee and head go to tail.

重定向头的输出到一个新的文件描述符，然后把它回来的作品，但我不知道这是干净，然后使用的/ dev / null的：

Redirecting the head's output to a new file descriptor and then taking it back works, but I am not sure it is "cleaner" then using /dev/null:

( tee >(head >&3) < text.txt | tail) 3>&1 

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