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10.5 Getting File Information

It is useful to find out information about a file before attempting to open, read or write to it. Perl provides a way to find out facts such as whether a file exists, how old it is, whether it a read-only or not. In fact there are 27 different tests you can perform on a file.

For example you can test to see if a file exists:

 die "Cannot create file. Already exists.\n"
		if -e "mydatafile"

The following table lists the full set of file tests available:

Operator	Meaning
-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.
-s	File has non-zero size (returns size).
	
-f	File is a plain file.
-d	File is a directory.
-l	File is a symbolic link.
-p	File is a named pipe (FIFO).
-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 a text file.
-B	File is a binary file (opposite of -T).
	
-M	Age of file (at startup) in days since modification.
-A	Age of file (at startup) in days since last access.
-C	Age of file (at startup) in days since inode change.

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