Shell internal commands and external commands

Shell internal commands and external commands

Internal command: is actually part of the shell program, which is a command executed by the shell itself, usually loaded and resides inside the system when the Linux system loads and runs.

External command: Is the utility part of the system, because the utility is usually more powerful, so the amount of programs involved will be very large, when the system is not loaded with the system is loaded into memory, but need to call memory. the entity of the external command is not included in the shell, but its command execution process is controlled by the shell, the shell program manages the path lookup, loading and storage of the external command execution, and controls the execution of the command. You can use the Echo $PATH command to view the storage path for external commands.

The type distinguishes between internal commands and external commands.

When executing a command, the shell command interpreter should execute the internal instruction first, and the instruction to execute is not an internal instruction, it should be the external instruction of the call.

View Shell internal commands: [...] #man Builtins

Determine if a command is an internal command: [...] #type-a command

[...] #command--help View Help files for external commands

[...] #help command to view Help files for internal commands

Shell internal commands and external commands