regex - Perl 就地替换

Question

在 Perl one liner 中，我们可以使用 -i 参数来进行就地替换。在 IDE 中编写 perl 代码时，-i 的等效项是什么？

考虑以下代码:

binmode(STDOUT, ':raw');
open my $fh, '<', $filename;
while (<$fh>) {
    s/^/<rootroot>/ if $.==1;
    if (/(<link rel[^<>\n]*?)(\/?)(>)/g) {
        my ($p1, $p2, $p3) = ($1, $2, $3);
        s/$p1$p2$p3/($p2 ? qq|$p1$p2$p3<span class="entry">| : qq|$p1\/$p3<span class="entry">|)/ge;
    };
    s/<\/>/<entry_end><\/entry_end>/;
    s/$/<\/rootroot>/ if eof;

}

我们如何就地保存所有更改行？

因为我需要在就地更改 html 源后立即使用 XML::LibXML 对 html 文件进行快速验证..

提前致谢。

Answer 1

你可以尝试这样的事情:

my $filename = 'test.dat';
@ARGV = ($filename);
$^I = '';
while(<<>>) {
    binmode(ARGV, ':raw');
    # Do the substitiution on $_ here ...
    print;
}

我没有找到如何设置 binmode在循环之前，因为 ARGV仅在 <> 之后定义运算符已被使用。

• $^I和 ARGV变量在 perlvar 中描述

• 参见 perlop有关为什么应该使用 <<>> 的信息而不是 <> .

一些注意事项:

• while(<>) { ... }根据perlop , 循环

while (<>) {  ...         # code for each line
}

is equivalent to the following Perl-like pseudo code:

unshift(@ARGV, '-') unless @ARGV;   
while ($ARGV = shift) { 
    open(ARGV, $ARGV);
    while (<ARGV>) {    
       ...        # code for each line    
    }  
}  

• 在没有备份文件的情况下使用就地编辑:$^I="" :

根据 perlrun :

If no extension is supplied, and your system supports it, the original file is kept open without a name while the output is redirected to a new file with the original filename. When perl exits, cleanly or not, the original file is unlinked.

更多信息请见this博客:

Perl opens and immediately unlink()s the original file, then opens a new file with the same name (new file descriptor and inode), and sends output to this second file; at the end, the old file is closed and thus deleted because it was unlinked, and what's left is a changed file with the same name as the original.

另见 doio.c用于实际实现。

• 根据以上内容，以下可能有效:

  my $fn = 'test.dat';
  open ( my $fh, '<:raw', $fn ) or die "Could not open file '$fn': $!";
  unlink $fn or die "$!";
  open ( my $fh2, '>:raw', $fn ) or die "Could not reopen file '$fn': $!";
  while(<$fh>) {
      # Do the substitutions on $_ here ...
      print $fh2 $_;
  }
  close $fh;
  close $fh2;