75 lines
2.1 KiB
Markdown
75 lines
2.1 KiB
Markdown
# Unix 管道
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> 原文:[https://python.land/the-unix-shell/unix-pipes](https://python.land/the-unix-shell/unix-pipes)
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管道将两个进程连接在一起。用`|`字符编写的管道将一个命令的输出连接到第二个命令的输入。这是 Unix shell 的基本构件之一。
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一个非常基本的例子是使用`cat`将文件内容输入字数统计工具`wc`:
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```py
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$ cat <filename> | wc
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```
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以防你不知道这些命令:
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* 打印文件的内容。
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* 对输入的所有行、字和字节进行计数。
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另一个常用的版本是`wc -l`，它只统计一个文件中的行数。
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让我们试试这个。首先，创建一个名为`words.txt`的文件，内容如下:
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```py
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hello
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world
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python
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ninja
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are
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you
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?
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3
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2
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1
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```
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然后运行以下命令:
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```py
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$ cat words.txt | wc -l
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```
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输出应该是 10，因为文件中有 10 行。另一个例子是使用`sort`对文件中的单词进行排序:
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```py
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$ cat words.txt | sort
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?
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are
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hello
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ninja
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python
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world
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you
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1
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2
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3
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```
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正如我们所看到的，来自`words.txt`的所有单词都被输入到`sort`中，由后者对它们进行排序。先标点，再数字，再字母。
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好吧。这是最后一个使用管道的有问题的例子。有一个很棒的工具叫做`cowsay`。它会生成一张 ASCII 图片，上面是一头牛在说你喂它的东西:
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```py
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$ echo "Are we going to learn anything useful?" | cowsay
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________________________________________
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< Are we going to learn anything useful? >
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----------------------------------------
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\ ^__^
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\ (oo)\_______
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(__)\ )\/\
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||----w |
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```
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这是会给你的同事留下持久印象的东西。 |