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The command "!${n}" is a way to refer to the value of a specific argument passed to a shell script or function. Here's how it works: 1. The "$n" syntax is used to access the value of the nth argument.

• For example, "$1" refers to the first argument, "$2" refers to the second argument, and so on. 2. The "!" symbol is used in combination with the "$n" syntax to expand the argument's value.
• This is known as history expansion or event designators in shells like bash. By using "!${n}", you can access and manipulate the value of an argument in various ways. For example, you can use it in a command to recall and execute a previous command with the nth argument as part of it. Here's an example to further illustrate: Let's say you have a shell script named "mycommand.sh" and you run it with two arguments: $ ./mycommand.sh argument1 argument2 Inside the script, if you want to access the value of the first argument, you can use: echo "$1" Similarly, if you want to use the value of the second argument in a command, you can use: !${2} This will expand to the value of the second argument. So, if the second argument is "argument2", the command "!${2}" will be equivalent to "argument2" and will have the same effect as directly using "argument2" in your script.