in reply to how to know the owner of the file in unix

You can use the stat function to retrieve the uid of the file.

perldoc -f stat stat FILEHANDLE stat EXPR stat Returns a 13-element list giving the status info for a file, either the file opened via FILEHANDLE, or named by EXPR. If EXPR is omitted, it stats $_. Returns a null list if the stat fails. Typically used as follows: ($dev,$ino,$mode,$nlink,$uid,$gid,$rdev,$size, $atime,$mtime,$ctime,$blksize,$blocks) = stat($filename); Not all fields are supported on all filesystem types. Here are the meanings of the fields: 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 in seconds since the epoch 9 mtime last modify time in seconds since the epoch 10 ctime inode change time in seconds since the epoch + (*) 11 blksize preferred block size for file system I/O 12 blocks actual number of blocks allocated

open MYFILE, '<filename' or die "Can not open: $!"; my $uid = (stat MYFILE)[4]; close MYFILE; print "UID = $uid\n";