For example if the user enters the command ps ael at the CS30 prompt the values

For example if the user enters the command ps ael at

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For example, if the user enters the command ps -ael at the CS30> prompt, the values stored in the args array are: args[0] = "ps" args[1] = "-ael" args[2] = NULL This args array will be passed to the execvp() function, which has the following prototype: execvp(char *command, char *params[]);
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Here, command represents the command to be performed and params stores the parameters to this command. For this project, the execvp() function should be invoked as execvp(args[0], args) Be sure to check whether the user included an & to determine whether or not the parent process is to wait for the child to exit. Part II Creating a History Feature The next task is to modify the shell interface program so that it provides a history feature that allows the user to access the most recently entered commands. The user will be able to access up to 10 commands by using the feature. The commands will be consecutively numbered starting at 1, and the numbering will continue past 10. For example, if the user has entered 35 commands, the 10 most recent commands will be numbered 26 to 35. The user will be able to list the command history by entering the command history at the CS30> prompt. As an example, assume that the history consists of the commands (from most to least recent): ps, ls -l, top, cal, who date The command history will output: 6 ps 5 ls -l 4 top 3 cal 2 who
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1 date Your program should support two techniques for retrieving commands from the command history: 1. When the user enters !!, the most recent command in the
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  • Fall '19
  • Exit, Child process, User Commands

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