perl one-liner 只保留所需的行 [英] perl one-liner to keep only desired lines

问题描述

我有一个这样的文本文件 (input.txt):

I have a text file (input.txt) like this:

NP_414685.4: 15-26, 131-138, 441-465
NP_418580.2: 493-500
NP_418780.2: 36-48, 44-66
NP_418345.2:
NP_418473.3: 1-19, 567-1093
NP_418398.2:

我想要一个 perl 单行，它只保留文件中:"后跟数字范围的那些行(这意味着，在这里，包含NP_418345.2:"和NP_418398.2:"的行被删除).为此，我尝试过:

I want a perl one-liner that keeps only those lines in file where ":" is followed by number range (that means, here, the lines containing "NP_418345.2:" and "NP_418398.2:" get deleted). For this I have tried:

perl  -ni -e "print unless /: \d/" -pi.bak input.txt del input.txt.bak

但它显示的输出与输入文件完全相同.我可以在这里匹配的确切模式是什么?谢谢

But it shows exactly same output as the input file. What will be the exact pattern that I can match here? Thanks

推荐答案

首先，print until 的意思是 print if not —— 与你想要的相反.

First, print unless means print if not -- opposite to what you want.

更重要的是，同时使用 -n 和 -p 是没有意义的，当你执行 -p 覆盖时另一个.当它们都打开输入文件并设置行循环时，-p 还为 每次 迭代打印 $_.所以有了它，你就重印了每一行.请参阅 perlrun.

More to the point, it doesn't make sense using both -n and -p, and when you do -p overrides the other. While both of them open the input file(s) and set up the loop over lines, -p also prints $_ for every iteration. So with it you are reprinting every line. See perlrun.

最后，您似乎要删除 .bak 文件...?那就别做了.只使用 -i

Finally, you seem to be deleting the .bak file ... ? Then don't make it. Use just -i

总和

perl -i -ne 'print if /:\s*\d+\s*-\s*\d+/' input.txt

如果您确实想保留备份文件，请使用 -i.bak 而不是 -i

If you do want to keep the backup file use -i.bak instead of -i

您可以使用 B::Deparse 查看与带有特定选项的单行代码等效的代码(通过 O 模块)

You can see the code equivalent to a one-liner with particular options with B::Deparse (via O module)

试试:perl -MO=Deparse -ne 1 和 perl -MO=Deparse -pe 1

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