Shell internal commands and external commands

Difference:

internal command: Internal commands are built into the shell. The internal command executes very quickly when the shell command is executed. This is because no other process has been created because of the execution of this command. For example, when we execute the "CD" command, no process is created. Simply change the current directory during execution. External command: The external command is not built into the shell. These executable external commands are stored in a separate file. When an external command is executed, a new process is created at the same time that the command is executed. For example, when we execute "LS" (usually saved in/bin
directory) command, then/usr/bin/cat is executed.

You can list all internal commands by entering help at the terminal.

Determine if a command is an internal command with type

CD is a shell builtin instructions CD is internal life. The other two is not an internal command.

When you do not know the specific usage of an internal command you can also use help like the use of jobs:

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Shell internal commands and external commands