perl - perl 的 int(-M $file) 有什么作用？

Question

我正在查看一些较旧的 perl 代码，我可以看到有人正在使用以下命令比较目录中各种文件的时间戳:

int(-M $filename);

这到底是做什么的？我查看了文档中的 int() 条目，但找不到有关 -M 标志的任何信息。

Answer 1

那是一个文件测试操作符-X

• -X FILEHANDLE
• -X EXPR
• -X DIRHANDLE

• -X

  A file test, where X is one of the letters listed below. This unary operator takes one argument, either a filename, a filehandle, or a dirhandle, and tests the associated file to see if something is true about it. If the argument is omitted, tests $_ , except for -t , which tests STDIN. Unless otherwise documented, it returns 1 for true and '' for false. If the file doesn't exist or can't be examined, it returns undef and sets $! (errno). Despite the funny names, precedence is the same as any other named unary operator. The operator may be any of:

  ...
  31.  -M  Script start time minus file modification time, in days.