What is the bash shell build in command?

What is the bash shell build in command 1. What is the build in command: The shell built-in command refers to the commands in the bash (or other versions) tool set. Generally, there is a system command with the same name. For example, the echo command in bash and/bin/echo are two different commands, although they are similar in behavior. When you type a command in bash, the system first checks whether it is a built-in command. If not, it checks whether it is a system command or a third-party tool. Therefore, in bash, type the echo command to execute the bash command in the bash tool set, that is, the built-in command, instead of the/bin/echo system command. 2. the built-in commands and system commands have higher execution efficiency than the system commands. When executing external commands, you often need to fork out (generate) A sub-process, while built-in commands are generally not used. The following (or later) article describes the built-in bash commands. 3. check whether a command is a system command or a built-in command: typehyk @ hyk-linux :~ /Documents $ type-a pwdpwd is a shell builtinpwd is/bin/pwd hyk @ hyk-linux :~ /Documents $ type-a echoecho is a shell builtinecho is/bin/echo. Some commands, echo and pwd are both built-in commands and system commands. 4. Common command types [root @ new55 ~] # Type-a cd is a shell builtin [root @ new55 ~] # Type-a pwd is a shell builtinpwd is/bin/pwd [root @ new55 ~] # Type-a time is a shell keywordtime is/usr/bin/time [root @ new55 ~] # Type-a date is/bin/date [root @ new55 ~] # Type-a which is aliased to 'Alias |/usr/bin/which -- tty-only -- read-alias -- show-dot -- show-tilde 'which is/usr/ bin/which [root @ new55 ~] # Type-a whereis is/usr/bin/whereis [root @ new55 ~] # Type-a whatis/usr/bin/whatis [root @ new55 ~] # Type-a function is a shell keyword [root @ new55 ~] # Type-a ls is aliased to 'ls -- color = tty 'ls is/bin/ls [root @ new55 ~] # Type-a ll is aliased to 'LS-l -- color = tty '[root @ new55 ~] # Type-a echo is a shell builtinecho is/bin/echo [root @ new55 ~] # Type-a bulitin-bash: type: bulitin: not found [root @ new55 ~] # Type-a builtin is a shell builtin [root @ new55 ~] # Type-a keyword-bash: type: keyword: not found [root @ new55 ~] # Type-a command is a shell builtin [root @ new55 ~] # Type-a alias is a shell builtin [root @ new55 ~] # Type-a grep is/bin/grep [root @ new55 ~] #