Which of the following commands puts the output of the command date into the shell variable mydate?
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A. B. C. D. E.A
The correct answer is A. mydate="$(date)".
Explanation:
The command date is used to display the current date and time on a Linux system. The question asks how to put the output of the date command into a shell variable named mydate.
A shell variable is a named value that can be used in a script or command-line session. To assign a value to a shell variable, you use the variable name followed by an equal sign and the value you want to assign. The correct answer to this question uses command substitution to assign the output of the date command to the mydate variable.
Command substitution is a shell feature that allows you to run a command and use its output as if it were a string. To use command substitution, you enclose the command in parentheses preceded by a dollar sign. The shell replaces the command substitution with the output of the command.
Option A, mydate="$(date)", uses command substitution to run the date command and assign its output to the mydate variable. The output of the date command is a string that contains the current date and time in a specific format.
Option B, mydate="exec date", assigns the string "exec date" to the mydate variable. This string is not the output of the date command, and it does not use command substitution to execute the date command.
Option C, mydate="$((date))", uses arithmetic expansion to try to evaluate the output of the date command as an arithmetic expression. This is not valid syntax and will result in an error.
Option D, mydate="date", assigns the string "date" to the mydate variable. This is not the output of the date command, and it does not use command substitution to execute the date command.
Option E, mydate="${date}", uses parameter expansion to try to reference a variable named date. This variable has not been previously defined in the script, so this will not work.
Therefore, option A, mydate="$(date)", is the correct answer to this question.