-p STDIN 在 Perl 中是什么意思？

Question

我看到这段代码

 if (-p STDIN) {
        while (<STDIN>) { ... }
 }

条件 -p STDIN 是什么意思？还有其他像-p?

Answer 1

这是一个文件测试操作员。这是来自 perldoc 的完整列表：

-r  File is readable by effective uid/gid.
-w  File is writable by effective uid/gid.
-x  File is executable by effective uid/gid.
-o  File is owned by effective uid.

-R  File is readable by real uid/gid.
-W  File is writable by real uid/gid.
-X  File is executable by real uid/gid.
-O  File is owned by real uid.

-e  File exists.
-z  File has zero size (is empty).
-s  File has nonzero size (returns size in bytes).

-f  File is a plain file.
-d  File is a directory.
-l  File is a symbolic link (false if symlinks aren't supported by the file system).
-p  File is a named pipe (FIFO), or Filehandle is a pipe.
-S  File is a socket.
-b  File is a block special file.
-c  File is a character special file.
-t  Filehandle is opened to a tty.

-u  File has setuid bit set.
-g  File has setgid bit set.
-k  File has sticky bit set.

-T  File is an ASCII or UTF-8 text file (heuristic guess).
-B  File is a "binary" file (opposite of -T).

-M  Script start time minus file modification time, in days.
-A  Same for access time.
-C  Same for inode change time (Unix, may differ for other platforms)

因此 -p 检查文件句柄（在本例中为 STDIN）是否附加到命名管道。

-p STDIN 在 Perl 中是什么意思？

What does -p STDIN mean in Perl?

perl