为什么在使用 ActivePerl 时必须指定带有备份扩展的 -i 开关? [英] Why do I have to specify the -i switch with a backup extension when using ActivePerl?

问题描述

除非我使用备份扩展指定它们，否则我无法在 ActivePerl 下就地编辑 Perl one-liners:

I cannot get in-place editing Perl one-liners running under ActivePerl to work unless I specify them with a backup extension:

C:> perl -i -ape "splice (@F, 2, 0, q(inserted text)); $_ = qq(@F
);" file1.txt
Can't do inplace edit without backup.

与 -i.bak 或 -i.orig 相同的命令可以工作，但在此过程中会创建不需要的备份文件.

The same command with -i.bak or -i.orig works a treat but creates an unwanted backup file in the process.

有没有办法解决这个问题?

Is there a way around this?

推荐答案

这是 Windows/MS-DOS 的限制.根据 perldiag:

This is a Windows/MS-DOS limitation. According to perldiag:

您使用的是诸如 MS-DOS 之类的系统，如果您尝试从已删除(但仍处于打开状态)的文件中读取，则会感到困惑.你必须说 -i.bak 或类似的.

You're on a system such as MS-DOS that gets confused if you try reading from a deleted (but still opened) file. You have to say -i.bak, or some such.

Perl 的 -i 实现会导致它删除 file1.txt，同时保持它的打开句柄，然后重新创建具有相同名称的文件.这允许您读取"file1.txt，即使它已被删除并正在重新创建.不幸的是，Windows/MS-DOS 不允许您删除附加了打开句柄的文件，因此该机制不起作用.

Perl's -i implementation causes it to delete file1.txt while keeping an open handle to it, then re-create the file with the same name. This allows you to 'read' file1.txt even though it has been deleted and is being re-created. Unfortunately, Windows/MS-DOS does not allow you to delete a file that has an open handle attached to it, so this mechanism does not work.

最好的办法是使用 -i.bak 然后删除备份文件.这至少为您提供了一些保护 - 例如，如果 perl 以非零退出代码退出，您可以选择不删除备份.类似的东西:

Your best shot is to use -i.bak and then delete the backup file. This at least gives you some protection - for example, you could opt not to delete the backup if perl exits with a non-zero exit code. Something like:

perl -i.bak -ape "splice...." file1.txt && del file1.bak

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