$realpath(<filepath>)

• If the <filepath> argument is omitted the empty string is returned.
• If the operating system does not have the realpath(3) function call, the <filepath> argument is returned.
• All directories, if any, in <filepath> must exist; if any of them do not exist the empty string is returned.
• The return function is the full absolute path of <filepath> with all symbolic links, `.', `..' and extra '/'s references resolved.
• This function calls the operating system's realpath(3) function.

Useful if you want to find the absolute path of filename with '.' or '..' or symbolic links in it.

The absolute path equivalent of <filepath>

If /home is a symbolic link to /usr/home, and /usr/local is a link to /local, then

$realpath(/home/../local/src)  returns "/local/src"

 (/home -> /usr/home
  ..    -> /usr
  local -> /local
  src   -> /local/src)