How to execute a self-written command (such as ls) in any folder under linux

We need to add the directory where the executable file is located to the PATH environment variable.

• 1
  sudo vim/etc/profile add a line: export PATH=$PATH:/script directory/
  remember to source and load the profile.
  There is a little problem with this: the colors on the command line are all gone

• 2
  sudo vim /etc/environment, add the directory to the back of the PATH. I used this
  and remember to source and load the profile

*3
Put the executable file directly into /usr/bin or /usr/local/bin, because these files are already in the PATH