10.4 Basic Command
10.4.1 “clear” Command – Clear Screen
When you work on the Shell Terminal, various contents are displayed on the screen. It can be inconvenient if the content of the screen is large or complex. In this case, you want to clear the current Terminal screen and start a new one. When you want to erase all the contents of the screen and start a new one, use the following command.
10.3.2 Applied Priority of Profile
When the system is started and a particular user logs on, what is applied to the system is the final result of the various profiles integrated according to their priority. By default, the local profile has priority over the global profile, and the application profile has a higher priority than the user profile.
The applied priority is that the above has a higher priority as shown below.
10.3 Shell and Profile
10.3.1 Type of Profile
There are many files and programs installed in the Raspberry Pi system. When working on the system, these items mutually interact with each other under certain control, and the necessary work is done. The results will vary depending on which files and which programs is used when you perform certain tasks. Therefore, in order for the system to operate consistantly, it is necessary to control the user’s working environment by instructing the system which program to use, which data to use, and how to operate.
10.2.2 Environment Variable
When the system is booted and a particular user logs on, the user is presented with a predefined screen and if the user issues a certain command, the command is processed in a predefined manner. At this time, the user confirms the contents defined in advance and determines the concrete processing method. When making important decisions that is necessary for the system to works, the system refers to a number of predefined data. Among these data, the important variables that the system frequently uses are stored in a special place, which is called an environment variable.