(870665) Please input your shell command: onechild (870665)Hello, I am a parent process (870666)Hello, I am a child process (870665) Please input your shell command: addnumbers (870665)Please input number, (0) to terminate 1 (870665)Read 1 (870665)Please input number, (0) to terminate (870667)The subtotal is: 1 2 (870665)Read 2 (870665)Please input number, (0) to terminate (870667)The subtotal is: 3 3 (870665)Read 3 (870665)Please input number, (0) to terminate (870667)The subtotal is: 6 4 (870665)Read 4 (870665)Please input number, (0) to terminate (870667)The subtotal is: 10 0 (870665)Read 0 (870667)The subtotal is: 10 (870665)The sum is 10 (870665) Please input your shell command: exec (870665) Please input exec subcommand ls ; a.out sample_run_1.txt solution.c (870665) Please input your shell command: processtree Please input the integer 3 (870665)The value is 0 (870671)The value is 4 (870672)The value is 2 (870676)The value is 3 (870674)The value is 1 (870673)The value is 6 (870675)The value is 5 (870677)The value is 7 (870665) Please input your shell command: stop