This function returns the name of a file pointed to by a symbolic link.
EXPR should evaluate to a filename, the last component of which
is a symbolic link.
If it is not a symbolic link, or if symbolic links
are not implemented, or if some system error occurs, the undefined
value is returned, and you should check the error code in
EXPR is omitted, the function uses $_.
Be aware that the returned symlink may be relative to the location you specified. For instance, you may say:
and readlink might return:
which is not directly usable as a filename unless your current directory happens to