LINUX Shell 命令 cat 和 grep
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/16961084/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
LINUX Shell commands cat and grep
提问by Vignesh T.V.
I am a windows user having basic idea about LINUX and i encountered this command:
我是一个对 LINUX 有基本概念的 Windows 用户，我遇到了这个命令：
cat countryInfo.txt | grep -v "^#" >countryInfo-n.txt
After some research i found that cat is for concatenation and grep is for regular exp search (don't know if i am right) but what will the above command result in (since both are combined together) ?
经过一些研究，我发现 cat 用于串联，而 grep 用于常规 exp 搜索（不知道我是否正确）但是上面的命令会导致什么结果（因为两者结合在一起）？
Thanks in Advance.
提前致谢。
EDIT: I am asking this as i dont have linux installed. Else, i could test it.
编辑：我问这个是因为我没有安装 linux。否则，我可以测试它。
采纳答案by DarkDust
Short answer: it removes all lines starting with a #and stores the result in countryInfo-n.txt.
简短回答：它删除所有以 a 开头的行#并将结果存储在countryInfo-n.txt.
Long explanation:
长解释：
cat countryInfo.txtreads the file countryInfo.txtand streams its content to standard output.
cat countryInfo.txt读取文件countryInfo.txt并将其内容流式传输到标准输出。
|connects the output of the left command with the input of the right command (so the right command can read what the left command prints).
|将左命令的输出与右命令的输入连接起来（因此右命令可以读取左命令打印的内容）。
grep -v "^#"returns all lines that do not(-v) match the regex ^#(which means: line starts with #).
grep -v "^#"返回所有不( -v) 匹配正则表达式的行^#（这意味着：行以 开头#）。
Finally, >countryInfo-n.txtstores the output of grepinto the specified file.
最后，>countryInfo-n.txt将 的输出存储grep到指定的文件中。
回答by shyam
It will remove all lines starting with #and put the output in countryInfo-n.txt
它将删除所有以开头的行#并将输出放入 countryInfo-n.txt
回答by devnull
This command would result in removing lines starting with #from the file countryInfo.txtand place the output in the file countryInfo-n.txt.
此命令将导致#从文件中删除以 开头的行countryInfo.txt并将输出放在文件中countryInfo-n.txt。
This command could also have been written as
这个命令也可以写成
grep -v "^#" countryInfo.txt > countryInfo-n.txt
See Useless Use of Cat.
请参阅Cat 的无用使用。
