When the command echo $? outputs 1, which of the following statements is true?



A. It is the process ID of the echo command.
B. It is the process ID of the current shell.
C. It is the exit value of the command executed immediately before echo.
D. It is the exit value of the echo command.

題解

「$?」儲存的值為上次命令執行結果的傳回值，所以答案是選項C。