Suppose I have a filehandle $fh. I can check its existence with -e $fh or its file size with -s $fh or a slew of additional information about the file. How can I get its last modified time stamp?
Calling the built-in function stat($fh) returns an array with the following information about the file handle passed in (from the perlfunc man page for stat):
0 dev device number of filesystem
1 ino inode number
2 mode file mode (type and permissions)
3 nlink number of (hard) links to the file
4 uid numeric user ID of file's owner
5 gid numeric group ID of file's owner
6 rdev the device identifier (special files only)
7 size total size of file, in bytes
8 atime last access time since the epoch
9 mtime last modify time since the epoch
10 ctime inode change time (NOT creation time!) since the epoch
11 blksize preferred block size for file system I/O
12 blocks actual number of blocks allocated
Element number 9 in this array will give you the last modified time since the epoch (00:00 January 1, 1970 GMT). From that you can determine the local time:
my $epoch_timestamp = (stat($fh))[9];
my $timestamp = localtime($epoch_timestamp);
Alternatively, you can use the built-in module File::stat (included as of Perl 5.004) for a more object-oriented interface.
And to avoid the magic number 9 needed in the previous example, additionally use Time::localtime, another built-in module (also included as of Perl 5.004). Together these lead to some (arguably) more legible code:
use File::stat;
use Time::localtime;
my $timestamp = ctime(stat($fh)->mtime);