Perl——文件操作

特殊文件句柄

perl提供了6种特殊的文件句柄:

STDIN ，

STDOUT ，

STDERR ，

DATA ，

ARGV，

ARGVOUT。

访问模式

模式	描述
< 或 r	只读方式打开，将文件指针指向文件头。
> 或 w	写入方式打开，将文件指针指向文件头并将文件大小截为零。如果文件不存在则尝试创建之。
>> 或 a	写入方式打开，将文件指针指向文件末尾。如果文件不存在则尝试创建之。
+< 或 r+	读写方式打开，将文件指针指向文件头。
+> 或 w+	读写方式打开，将文件指针指向文件头并将文件大小截为零。如果文件不存在则尝试创建之。
+>> 或 a+	读写方式打开，将文件指针指向文件末尾。如果文件不存在则尝试创建之。

文件测试

File Test	Meaning
-r	File or directory is readable by this (effective) user or group
-w	File or directory is writable by this (effective) user or group
-x	File or directory is executable by this (effective) user or group
-o	File or directory is owned by this (effective) user
-R	File or directory is readable by this real user or group
-W	File or directory is writable by this real user or group
-X	File or directory is executable by this real user or group
-O	File or directory is owned by this real user
-e	File or directory name exists
-z	File exists and has zero size (always false for directories)
-s	File or directory exists and has nonzero size (the value is the size in bytes)
-f	Entry is a plain file
-d	Entry is a directory
-l	Entry is a symbolic link
-S	Entry is a socket
-p	Entry is a named pipe (a “fifo”)
-b	Entry is a block-special file (like a mountable disk)
-c	Entry is a character-special file (like an I/O device)
-u	File or directory is setuid
-g	File or directory is setgid
-k	File or directory has the sticky bit set
-t	The filehandle is a TTY (as reported by the isatty() system function; filenames can’t be tested by this test)
-T	File looks like a “text” file
-B	File looks like a “binary” file
-M	Modification age (measured in days)
-A	Access age (measured in days)
-C	Inode-modification age (measured in days)

if (-r $filename and -w $filename) {
... }

• 文件测试操作符没写文件名和文件句柄,则默认文件名保存在$_里

foreach (@lots_of_filenames) {
print "$_ is readable\n" if -r;
}

select

使用select更改默认文件输出句柄