To solve this question, the user needs to have knowledge of basic programming and shell scripts.
Option A is incorrect because the variable $tree
is not enclosed in quotes, which will result in a syntax error. The correct way to assign a string value to a variable in PHP is to enclose it in quotes. Thus, the correct syntax for option A is $tree = "maple";echo $tree
Option B is incorrect because the variable tree
is not preceded by a dollar sign $
, which will result in a syntax error. Thus, the correct syntax for option B is $tree = "maple"; echo $tree
Option C is incorrect because the export
command is used to set an environment variable so that it can be accessed by child processes. In this case, the sh -c
command creates a new shell process and prints the value of the environment variable $tree
. However, since the variable was not exported, it will not be accessible by the new shell process, and the output will be empty. Thus, the correct syntax for option C is tree=maple; export tree; sh –c "echo $tree"
Option D is correct because it correctly assigns the string value "maple" to the variable tree
, exports it so that it can be accessed by child processes, and then prints its value using the sh -c
command. Thus, the correct answer is:
The Answer is: D