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Enable starts or disables shell built-in commands

Summary enable [- a] [- dnps] [- f filename] [name …]

The main purpose is to disable one or more built-in commands.

Enable one or more built-in commands.

Directly invoke an external command with the same name as the disabled built-in command and found under the $PATH path.

Print all built-in commands, whether disabled or not.

Print built-in commands that are enabled.

Print built-in commands that are disabled.

Print posix standard built-in commands that are enabled.

Print posix standard built-in commands that are disabled.

Print posix standard built-in commands, whether disabled or not.

Load built-in commands from the dynamic library.

Removes built-in commands loaded from the dynamic library.

Option-a prints all built-in commands, whether disabled or not. -d removes built-in commands loaded from the dynamic library. -n disable built-in commands or display disabled built-in commands. -p prints in a reusable format. -s displays only posix standard built-in commands that are in the startup state. -f load built-in commands in the dynamic library. -ns prints posix standard built-in commands that are disabled. -as prints posix standard built-in commands, whether disabled or not. Parameter filename: dynamic library file name.

Name (optional): built-in commands, which can be multiple.

The return value enable returns success unless name is not a built-in command or an error occurs.

Example (the following is limited to the section that no longer lists the return values) # posix special builtin # assumes that no built-in commands are disabled # disable two posix standard built-in commands enable-n set source # print the disabled posix standard built-in commands enable-ns # print posix standard built-in commands, whether disabled or not Enable-as # Printing the posix standard built-in command enable-s # assumes that no built-in commands are disabled # disable one or more built-in commands enable-n echo pwd # print all built-in commands, whether disabled or not Enable-a # print enabled built-in commands enable # print disabled built-in commands enable-n # enable one or more built-in commands enable pwdQ&AQ: what about the demo of-fmai?

A: to explain,-f and-d are limited to personal ability and do not find a suitable example. If you have a better example, you are welcome to mention pr;. I have verified that there seems to be no difference in the use of the-p option. What is the difference between enable-p | cat-An and enable | cat-A? (note: cat-An is used to display invisible characters)

Q: can I disable enable itself? Can you disable or enable built-in commands after that?

A: yes; no.

Note that when the linux shell command is executed, shell always looks for the command in its own shell builtin first, and executes it if it is found; if it cannot be found, it looks for the command to be executed in turn from the path specified by the environment variable $PATH. There seems to be no way to write your own commands instead of shell builtin commands. Fortunately, we can do it with the enable command.

When the built-in command echo is not disabled, you can only write / usr/bin/echo if you want to call the external command echo

When we disable echo, the priority order is as follows:

Function > external command

If the environment in which the command is executed does not have an echo function, then the echo called is an external command.

This command is a bash built-in command. For help, please see the help command.

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