打印 Perl s///g 中发生了多少次替换? [英] Print how many substitutions took place in a Perl s///g?
问题描述
我使用了网络搜索,发现了类似标题的问题 Perl s///g 中发生了多少次替换? 并尝试使用它来打印数字但未能成功.
I've used web search, found similarly titled question How many substitutions took place in a Perl s///g? and tried to use it to print the number but have not been able to succeed.
我的初始代码是
perl -0777 -i.original -pe 's-\r\n-\n-igs' test.txt
当我尝试
perl -0777 -i.original -pe "$c=s-\r\n-\n-igs;say qq'$c'" test.txt
当我尝试时,我一无所获 - 没有输出也没有替换
I got nothing - no output and no replacements, when I tried
perl -0777 -i.original -pe '$c=s-\r\n-\n-igs;print qq($c\n)' test.txt
(print
类似于我之前使用的其他单行代码)我在标准输出中得到了空字符串,但是 454847
添加为文件的开头(和适当的替换).
(print
similar to other one-liners I used before) I got empty string in standard output but 454847
added as the beginning of file (and proper replacements).
我知道在我的情况下不需要 =~
(什么=~ 在 Perl 中是做什么的?),那么我的代码有什么问题?如何打印替换次数?
I understand =~
is not needed in my case (What does =~ do in Perl?), so what is wrong with my code? How to print number of replacements made?
推荐答案
由于 -i
,默认的输出句柄不是 STDOUT 而是输出文件.要打印到 STDOUT,您需要明确地这样做.
Because of -i
, the default output handle isn't STDOUT but the output file. To print to STDOUT, you'll need to do so explicitly.
如果使用 cmd
shell,
If using the cmd
shell,
perl -0777pe"CORE::say STDOUT s/\r//g" -i.original test.txt
如果使用 sh
或类似的,
If using sh
or similar,
perl -0777pe'CORE::say STDOUT s/\r//g' -i.original test.txt
注意事项:
s///
比s---
更惯用/i
在这里没用./s
在这里没用.- 检查换行符毫无意义.
s/\r//g
将与s/\r\n/\n/g
一样工作. - 使用变量进行计数是有意义的,尤其是在使用
say
而不是print
时. - 出于向后兼容性的原因,必须使用
CORE::say
而不是say
,除非使用use feature qw( say );
或等效物. s/\r\n/\n/g
和s/\r//g
都不能用于 Perl 的 Windows 版本,而且没有办法在 Windows 版本的 Perl 上使用-i
时做你想做的事.但是,您使用的是 Perl 的 unix 版本(因为 MSYS 是一个 unix 仿真环境),所以这不是问题.
s///
is more idiomatic thans---
/i
is useless here./s
is useless here.- There no point in checking for Line Feeds.
s/\r//g
will work just as fine ass/\r\n/\n/g
. - There's point in using a variable for the count, especially if using
say
instead ofprint
. - One must use
CORE::say
instead ofsay
for backwards compatibility reasons unlessuse feature qw( say );
or equivalent is used. - Neither
s/\r\n/\n/g
nors/\r//g
will work with a Windows build of Perl, and there's no way to do what you want when using-i
on a Windows build of Perl. However, you are using a unix build of Perl (since MSYS is a unix emulation environment), so it's not an issue.
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