Article directory
cupsenable
Start the specified printer
Additional information
cupsenableCommand is used to start the specified printer.
grammar
cupsenable [选项] [目标]
Options
-E: Force the use of encryption when connecting to the server.-U: Specify the username used when connecting to the server.-u: Specify the user to whom the print task belongs.-h: Specify the server name and port number to connect to.
parameter
- Destination: Specify the destination printer.
enable
Enable or disable shell builtins
overview
enable [-a] [-dnps] [-f filename] [name …]
The main purpose
- Disable one or more built-in commands.
- Enable one or more built-in commands.
- Directly calls
$PATHan external command with the same name as the disabled built-in command and found in the path. - Print all built-in commands, whether disabled or not.
- Prints the enabled built-in commands.
- Print built-in commands that are disabled.
- Prints the POSIX standard built-in commands that are enabled.
- Prints the disabled POSIX standard built-in command.
- Prints the POSIX standard built-in command, whether disabled or not.
- Load built-in commands from dynamic libraries.
- Remove built-in commands loaded from dynamic libraries.
Options
-a: Print all built-in commands, whether disabled or not.-d: Remove built-in commands loaded from dynamic libraries.-n: Disable built-in commands or display disabled built-in commands.-p: Print in reusable format.-s: Only display POSIX standard built-in commands in the started state.-f: Load built-in commands in the dynamic library.-ns: Print POSIX standard built-in commands that are disabled.-as: Print POSIX standard built-in commands, whether disabled or not.
parameter
filename:Dynamic library file name.name(Optional): Built-in command, there can be multiple.
return value
enableReturns successful unless nameit is not a built-in command or an error occurs.
example
# posix special builtin
# 假设没有任何内建命令被禁用
# 禁用两个 posix 标准内建命令
enable -n set source
# 打印处于禁用状态的 posix 标准内建命令
enable -ns
# 打印 POSIX 标准内建命令，无论是否禁用。
enable -as
# 打印处于启用状态的 POSIX 标准内建命令
enable -s
# 假设没有任何内建命令被禁用
# 禁用一到多个内建命令
enable -n echo pwd
# 打印所有内建命令，无论是否禁用。
enable -a
# 打印处于启用状态的内建命令
enable
# 打印处于禁用状态的内建命令
enable -n
# 启用一到多个内建命令
enable pwd
Q&A
Q: What about -fthe demonstration -dof -p?
A: To explain, I have not found a suitable example -fdue -dto my personal ability. If you have a better example, please submit a PR. After I verified that -pthere seems to be no difference whether the option is used, you can compare enable -p | cat -Aand enable | cat -Awhat is the difference. (Note: cat -Aused to display invisible characters)
Q: Is it possible to disable enablemyself? Can I still disable or enable built-in commands later?
A: Yes; no.
Notice:
When a Linux Shell command is executed, the Shell always first searches for the command in its own Shell builtin. If it is found, the command is executed; if the command is not found, the command to be executed is searched sequentially from the $PATHpath specified by the environment variable. . It seems that there is no way to write user's own commands to replace the Shell builtin commands. Fortunately, with enablethe command we can do just that.
For knowledge about the priority of calling commands with the same name, please first refer to the prompt part of the builtin command, and then continue reading the following part; when the built-in command is echonot disabled, if you want to call an external command echo, you can only write like this /usr/bin/echo; when we disable it echo, The priority order becomes this:
Functions > External Commands
If the environment in which the command is executed does not have a function, then the external command is echocalled .echo
This command is a built-in command of Bash. For related help information, please see helpcommand.
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