每个Perl黑客应该知道perl -ne是什么？ [英] What should every Perl hacker know about perl -ne?

问题描述

多年来，我一直使用Perl命令行与 -ne 选项，主要是处理文本文件的方式，sed不能。示例：

  cat in.txt | perl -nes / abc / def /; s / fgh / hij /; print; > out.txt 
  

我不知道从哪里学到这个，今天只读了 perlrun ，发现还有其他形式（ perl -pe



我还应该知道 perl -ne ？

解决方案

perl -ne'CODE'等同于程序

  while（<>）{
 CODE 
} 
  pre> 
 
 
  perl -ane'CODE'和 perl -F / PATTERN / 也是很好的成语要知道。它们等同于
  while（<>）{
 @F = split / \s + $ _; 
 CODE 
} 
  
和
  while（<>）{
 @F = split / PATTERN /，$ _ 
 CODE 
} 
  
示例： advanced grep  ：
  perl -ne'print if / REGEX1 /&&！/ REGEX2 /& || / REGEX4 /&&！/ REGEX5 /）'输入
 
 perl -F /，/-如果$ F [2] = 4& $ F ] ge2009-07-01&& $ F [3] lt2009-08-01'file.csv 
  
 
 
 
 
 
使用不匹配大括号的一个特别聪明的例子是这里。
 
I have been using the Perl command line with a -ne option for years, largely to process text files in ways that sed can't. Example:
cat in.txt | perl -ne "s/abc/def/; s/fgh/hij/; print;" > out.txt
I have no idea where I learned this, and have only today read perlrun and found there are other forms (perl -pe for example).

What else should I know about perl -ne?
解决方案
perl -ne 'CODE' is equivalent to the program
while (<>) {
    CODE
}
perl -ane 'CODE' and perl -F/PATTERN/ -ane are also good idioms to know about. They are equivalent to
while (<>) {
    @F = split /\s+/, $_;
    CODE
}
and
while (<>) {
    @F = split /PATTERN/, $_;
    CODE
}
Example:  advanced grep:
perl -ne 'print if/REGEX1/&&!/REGEX2/&&(/REGEX3/||/REGEX4/&&!/REGEX5/)' input

perl -F/,/ -ane 'print if $F[2]==4&&$F[3]ge"2009-07-01"&&$F[3]lt"2009-08-01"' file.csv


A particularly clever example that uses mismatched braces is here.

                        
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