丢弃的输出(Discard the output)(过滤的输出)

最新推荐文章于 2024-06-20 11:10:16 发布

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原文链接：https://my.oschina.net/Xiao629/blog/271489

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本文介绍了如何使用重定向命令来控制命令输出及错误信息流向特殊文件 /dev/null 的方法，包括如何仅丢弃输出、如何同时丢弃输出和错误信息等技巧。

2019独角兽企业重金招聘Python工程师标准>>>

Sometimes you will need to execute a command, but you don't want the output displayed to the screen. In such cases you can discard the output by redirecting it to the file /dev/null:

$ command > /dev/null

Here command is the name of the command you want to execute. The file /dev/null is a special file that automatically discards all its input.

To discard both output of a command and its error output, use standard redirection to redirect STDERR to STDOUT:

$ command > /dev/null 2>&1

Here 2 represents STDERR and 1 represents STDOUT. You can display a message on to STDERR by redirecting STDIN into STDERR as follows:

$ echo message 1>&2

Redirection Commands:

Following is the complete list of commands which you can use for redirection:

Command	Description
pgm > file	Output of pgm is redirected to file
pgm < file	Program pgm reads its input from file.
pgm >> file	Output of pgm is appended to file.
n > file	Output from stream with descriptor n redirected to file.
n >> file	Output from stream with descriptor n appended to file.
n >& m	Merge output from stream n with stream m.
n <& m	Merge input from stream n with stream m.
<< tag	Standard input comes from here through next tag at start of line.
\|	Takes output from one program, or process, and sends it to another.