Hacker: It refers to the skilled computer experts who, with the help of their technical knowledge, uses bugs or try to exploit and break into the computer systems. The term “hacker” can be also defined as the one who destabilizes the computer security .

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Whentheuserenters!!,themostrecentcommandinthehistoryisexecuted.In the example above, if the user entered the command: Osh> !! The ‘ls -l’ command should be executed and echoed on user’s screen. The command should also be placed in the history buffer as the next command. Whentheuserentersasingle!followedbyanintegerN,theNthcommandin the history is executed. In the example above, if the user entered the command: Osh> ! 3 The ‘ps’ command should be executed and echoed on the user’s screen. The command should also be placed in the history buffer as the next command. Error handling: The program should also manage basic error handling. For example, if there are no commands in the history, entering !! should result in a message “No commands in history.” Also, if there is no command corresponding to the number entered with the single !, the program should output "No such command in history."

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Chapter 2, Problem 9RQ

Program Plan Intro

Hacker:

It refers to the skilled computer experts who, with the help of their technical knowledge, uses bugs or try to exploit and break into the computer systems. The term “hacker” can be also defined as the one who destabilizes the computer security.

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Whentheuserenters!!,themostrecentcommandinthehistoryisexecuted.In the example above, if the user entered the command: Osh> !! The ‘ls -l’ command should be executed and echoed on user’s screen. The command should also be placed in the history buffer as the next command. Whentheuserentersasingle!followedbyanintegerN,theNthcommandin the history is executed. In the example above, if the user entered the command: Osh> ! 3 The ‘ps’ command should be executed and echoed on the user’s screen. The command should also be placed in the history buffer as the next command. Error handling: The program should also manage basic error handling. For example, if there are no commands in the history, entering !! should result in a message “No commands in history.” Also, if there is no command corresponding to the number entered with the single !, the program should output "No such command in history."

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2. UNIX Shell and History Feature [20 points] This question consists of designing a C program to serve as a shell interface that accepts user commands and then executes each command in a separate process. A shell interface gives the user a prompt, after which the next command is entered. The example below illustrates the prompt osh> and the user's next command: cat prog.c. The UNIX/Linux cat command displays the contents of the file prog.c on the terminal using the UNIX/Linux cat command and your program needs to do the same. osh> cat prog.c The above can be achieved by running your shell interface as a parent process. Every time a command is entered, you create a child process by using fork(), which then executes the user's command using one of the system calls in the exec() family (as described in Chapter 3). A C program that provides the general operations of a command-line shell can be seen below. #include #include #define MAX LINE 80 /* The maximum length command */ { int…