Perl中的if(-f< filename>)有什么作用? [英] What does if( -f <filename> ) in Perl do?

问题描述

我遇到了以下代码行:

if( -f <filename> ) { ... }

-f似乎在测试文件名是否存在，但我不确定.到目前为止，Google尚无帮助(Google很难找到"-f")，也没有我的Perl书籍.

-f appears to test whether the filename exists or not, but I am not sure. Googling has not helped so far (it is hard to Google for "-f") and neither have my Perl books.

任何人都可以请教吗?

推荐答案

请参见 perlfunc .

它列出了所有Perl内置功能，包括文件测试"功能:

It lists all the Perl built-in functions, including the "file test" ones:

-X FILEHANDLE
-X EXPR
-X DIRHANDLE
-X

其中-X是以下之一:

-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.
-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 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)

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