To learn more about the dart command, run dart -h
  from the command line, or see the dart tool page.

Update path directly

In some cases, your distribution may not permanently acquire
the path when using the above directions. When this occurs,
you can change the environment variables file directly.
These instructions require administrator privileges:

Determine the path of your clone of the Flutter SDK.

Locate the etc directory at the root of the system,
and open the profile file with root privileges.

    
  $ sudo nano /etc/profile

Update the PATH string with the location of your
Flutter SDK directory.

    
if [ "`id -u`" -eq 0 ]; then
   PATH="..."
else
   PATH="/usr/local/bin:...:[PATH_OF_FLUTTER_GIT_DIRECTORY]/bin"
fi
export PATH

End the current session or reboot your system.