Computer Systems: A Programmer's Perspective (3rd Edition)
3rd Edition
ISBN: 9780134092669
Author: Bryant, Randal E. Bryant, David R. O'Hallaron, David R., Randal E.; O'Hallaron, Bryant/O'hallaron
Publisher: PEARSON
expand_more
expand_more
format_list_bulleted
Videos
Textbook Question
Chapter 8, Problem 8.22HW
Write your own version of the Unix system function
int mysystem(char *command);
The mysystem function executes command by invoking /bin/ sh -c command, and then returns after command has completed. If command exits normally (by calling the exit function or executing a return statement), then mysystem returns the command exit status. For example, if command terminates by calling exit (8), then mysystem returns the value 8. Otherwise, if command terminates abnormally, then mysystem returns the status returned by the shell.
Expert Solution & Answer
Trending nowThis is a popular solution!
Students have asked these similar questions
In this laboratory work, you are expected to write a c# console application to make someoperations about the customers. Operations and required featurest that you need to cover inyour program are following:• Add: This function adds a new person to json file. You need to get inputs from userand adds the new one into json file.• Display: This function displays all people in your json file.• Search: This function let you search with the user id.• Create Password: This function will create a random password for the user and usermay choose the length of the password. Password may include numbers andcharacters.• Exceptions: You need to handle exceptions as well. You should at least handle 3 ofexceptional cases. For the case that file can not be found, It is mandatory to catch theexception.
In python, rite a recursive function, displayFiles, that expects a pathname as an argument. The path name can be either the name of a file or the name of a directory. If the pathname refers to a file, its filepath is displayed, followed by its contents, like so:
File name: file_path Lorem ipsum dolor sit amet, consectetur adipiscing elit...
Otherwise, if the pathname refers to a directory, the function is applied to each name in the directory, like so:
Directory name: directory_path File name: file_path1 Lorem ipsum dolor sit amet... File name: file_path2 Lorem ipsum dolor sit amet... ...
Test this function in a new program.
Please assist, I am trying to modify the function so that it checks if the user is trying to register a name that already exists in user.txt, the appropriate message is displayed but it does not loop back to requesting the user to enter a new username. Instead it continues to request a password from the user.
Here is what I have so far in Python.
# Define a function to register a new user.def reg_user(): while True: if menu == "r": if user_name == "admin" and password == "adm1n": new_user = input("Please enter a new username: ").lower() with open ("user.txt", "r") as new_file: read_file = new_file.readlines() for file in read_file: read_file = file.split(",") if new_user == read_file[0]: print("Invalid input. This user already exists.") new_password = input("Please enter the password for the new user:…
Chapter 8 Solutions
Computer Systems: A Programmer's Perspective (3rd Edition)
Ch. 8.2 - Prob. 8.1PPCh. 8.4 - Prob. 8.2PPCh. 8.4 - Prob. 8.3PPCh. 8.4 - Prob. 8.4PPCh. 8.4 - Practice Problem 8.5 (solution page 797) Write a...Ch. 8.4 - Practice Problem 8.6 (solution page 797) Write a...Ch. 8.5 - Practice Problem 8.7 (solution page 798) Write a...Ch. 8.5 - Prob. 8.8PPCh. 8 - Prob. 8.9HWCh. 8 - In this chapter, we have introduced some functions...
Ch. 8 - How many hello output lines does this program...Ch. 8 - How many "hello' output lines does this program...Ch. 8 - Prob. 8.13HWCh. 8 - How many hello output lines does this program...Ch. 8 - How many "hello lines does this program print?Ch. 8 - Prob. 8.16HWCh. 8 - Prob. 8.17HWCh. 8 - Consider the following program: Determine which of...Ch. 8 - How many lines of output does the following...Ch. 8 - Use execve to write a program called my1s whose...Ch. 8 - What are the possible output sequences from the...Ch. 8 - Write your own version of the Unix system function...Ch. 8 - One of your colleagues is thinking of using...Ch. 8 - Modify the program in Figure 8.18 so that the...Ch. 8 - Write a version of the fgets function, called...
Additional Engineering Textbook Solutions
Find more solutions based on key concepts
Write an SQL statement to display the breed, type, and DOB for all pets having the type Dog and the breed Std. ...
Database Concepts (7th Edition)
Prove that the eigenvalue problem y+y=0;y(0)=0,y(1)=y(1)=0 has no negative eigenvalues. (Suggestion: Show graph...
Differential Equations: Computing and Modeling (5th Edition), Edwards, Penney & Calvis
When one object is a specialized version of another object, there is an_________ between them. a. is a relation...
Starting out with Visual C# (4th Edition)
In Exercises 11 through 16, determine the errors. PrivateSubbtnOutputClick(...)HandlesbtnOutput.ClicktxtBox=Hel...
Introduction To Programming Using Visual Basic (11th Edition)
Is the following valid if ShapeBaSe is defined as in Listing 8.19? ShapeInterface shapeVariable = new ShapeBase...
Java: An Introduction to Problem Solving and Programming (7th Edition)
(Asterisked problems are associated with optional sections.) 3. Rework Problem 2 assuming column major order ra...
Computer Science: An Overview (13th Edition) (What's New in Computer Science)
Knowledge Booster
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, computer-science and related others by exploring similar questions and additional content below.Similar questions
- Write a recursive function, displayFiles, that expects a pathname as an argument. The path name can be either the name of a file or the name of a directory. If the pathname refers to a file, its filepath is displayed, followed by its contents, like so: File name: file_path Lorem ipsum dolor sit amet, consectetur adipiscing elit... Otherwise, if the pathname refers to a directory, the function is applied to each name in the directory, like so: Directory name: directory_path File name: file_path1 Lorem ipsum dolor sit amet... File name: file_path2 Lorem ipsum dolor sit amet... ... # Put your code here import os #module used to interact with operating system def displayFiles(pathname): #recursive function that takes a pathname as argument if (os.path.isdir(pathname)): #checks if specified path (argument) is an existing directory #for item in os.listdir(pathname): for content in os.listdir(pathname): #gets the list of all files and directories in the directory and…arrow_forwardWrite a recursive function, displayFiles, that expects a pathname as an argument. The path name can be either the name of a file or the name of a directory. If the pathname refers to a file, its filepath is displayed, followed by its contents, like so: File name: file_path Lorem ipsum dolor sit amet, consectetur adipiscing elit... Otherwise, if the pathname refers to a directory, the function is applied to each name in the directory, like so: Directory name: directory_path File name: file_path1 Lorem ipsum dolor sit amet... File name: file_path2 Lorem ipsum dolor sit amet... ...arrow_forwardIn C write a program that takes a file name and two strings as command line arguments, and writes the longer of the two strings to the file with the given name. If the given strings are the same length, write the first string given to the file. If the user does not provide the correct number of command line arguments, print an error message and exit the program with a non-zero exit code.arrow_forward
- Use the Bash shell for the completion of this project. Develop a shell scripting application that allows the user to perform some advanced mathematical operations. Your application should allow the user to perform these tasks: Task 2: Find the term of any linear sequence given by the rule Term = a * n + b, where a and b are integers specified by the user and n is a positive integer and print them in order (for example if the user inputs a=3, b=-4, the first few terms that should be printed are -1, 2, 5, 8, 11…). The user also will specify how many terms the program should print. In addition, the program should print the sum of terms found and a count of how many odd terms were found.arrow_forwardPlease Code this in C. Purpose is to show shared memory in Unix environment. In this assignment, you will create 4 processes. Each of these processes will share a variable called "total". Each will increment the variable “total” by one to 100,000, 200,000, 300,000 and 500,000 respectively. Make sure that only the newly created child calls the function “process#()” After all the children have finished, the parent process should release the shared memory and terminate. Use the "wait" function so that the parent knows precisely when each of the children finishes. The parent should print the process id of each child as the child finishes execution. Then it should release shared memory and print "End of Program". Sample output From Process 1: counter = 270547. From Process 2: counter = 347860. From Process 3: counter = 400001. From Process 4: counter = 500000. Child with ID: 2412 has just exited. Child with ID: 2411 has just exited. Child with ID: 2413 has just exited. Child with…arrow_forwardYour task is to implement a variation of the classic word game Hangman, which involves players guessing the letters in a word chosen at random with a finite number of guesses. While there are alternate versions such as category Hangman and Wheel of Fortune, which involve players guessing idioms, places, names and so on, we will be sticking with the traditional version. Requirements:You will implement a function called main that allows users to play an interactive hangman game against the computer. The computer should pick a word, and players should then try to guess letters in the word until they win or run out of guesses.Here is the overarching behaviour we expect:1. The program should load a list of available words from the text file provided. Note that the file you have been given contains words in lowercase.2. The computer should then select a word at random from the list at random.3. The user is given a certain number of guesses at the beginning.4. The game is interactive; the…arrow_forward
- Write a function called user_input() that takes an integer n as a parameter. Thisfunction should display the integer n to the user and prompt them to enter its equivalentbinary value (the user just has to make a guess here). Your function should return theuser input.arrow_forwardCode done in C Write a piece of code in a function called password that creates a file with a random password (it can be a number). In another function called check_password, the function must ask the user to input the password to login and it should match the password in the file. If it doesn't, it should keep asking the user to keep inputting the right password. Finally, just by passing in the two functions into the main, that would be fine. Ex. int main() { ....password(....); ....check_password(....); }arrow_forwardWrite in C for STM32F446RE microcontroller on the Nucleo-64 dev board uncluding proper header files Write a source library that contains the with the following public functions: void keypadInit(void); /Initiallized the GPIO to read the keypad. uint16_t readKeypad(void); //Returns the state of all of the keypad buttons in the return value at the moment the function is called. void decodeKeypad(uint16_t, char *); //Takes the state of the keypad and returns (by reference) an array of the key's pressed. The library should work with the following main: int main (void) { uint16_t key; char carray[17]; keypadInit(); while(1) { while(!(key = readKeypad())); /*Get which keys pressed*/ decodeKeypad(key, carray); /*What are those keys*/ printf("%s\n",carray); /*Print those keys to screen*/ while(readKeypad() == key); /*Wait for the keypad to change*/ }} Problem 1: Write a library that works with the following…arrow_forward
- The Directory class has a list of names in it. You should use dynamic memory to create anarray upon instantiation. You should create a copy constructor for the directory class and anassignment operator (i.e. operator=()). You should create a function called fillDirectory whichaccepts a size for the directory and the names for it both of which should be given by the user.In main, create directory1 and fill it with information. Use the assignment operator=() to setdirectory2 equal to directory1. This is in c++arrow_forwardwith python do whis: Edit or delete a user profileWhen the user chooses 2, the first thing that it should do is to check whether the user information is loaded in the program (i.e., check if the user information is passed to the function that generates recipe recommendations). If the user information is passed to the function (i.e., the user chose option 1 before choosing option 2), the program should show the user the following menu:Hello (user name)You can perform one of the following operations:1) Delete your profile2) Edit your profilea. If the user chooses 1, perform the following subtasks to delete a user profile:1- Search for the user profile in the file userInformation.txt using the user name in read mode; once you find the user profile (i.e., the line that contains all the user information), pass it to a function that deletes the user information.2- The function should create a temporary file called temp.txt in write mode and search the file userInformation.txt in read mode…arrow_forwardComplete the process_name() function that takes a single string parameter name. You can assume that the name will always be in the format first name surname with a single space character between the first name and the surname. The function returns a string consisting of the first letter of the first name followed by the first three letters of the surname. All of the characters in the returned string should be in lowercase. Some examples of the function being used are shown below: For example: Test Result print(process_name("Damir Azhar")) dazh print(process_name("Ann Cameron")) acam Answer: (penalty regime: 0 %) Reset answer 1v def process_name (name): 2arrow_forward
arrow_back_ios
SEE MORE QUESTIONS
arrow_forward_ios
Recommended textbooks for you
Programming with Microsoft Visual Basic 2017Computer ScienceISBN:9781337102124Author:Diane ZakPublisher:Cengage Learning
Programming with Microsoft Visual Basic 2017
Computer Science
ISBN:9781337102124
Author:Diane Zak
Publisher:Cengage Learning
Instruction Format (With reference to address); Author: ChiragBhalodia;https://www.youtube.com/watch?v=lNdy8HREvgo;License: Standard YouTube License, CC-BY