Chapter 7 Shell Scripting Part I Your Answers For These Labs

Chapter 7 Shell Scripting Part Iiyour Answers For These Labs Will B

Chapter 7: Shell Scripting (part II) Your answers for these labs will be the script you come up with for each step. 1. Write a script to compute payroll information for the people in the employees.txt file that you downloaded. Each row of this file consists of a person’s last name, hours and wages. To compute pay, use an if-then-else statement using this formula: Hours wages; Hours > 40 — pay = 40 wages + 2 (hours – 40) wages. We can’t use time and a half (1.5) for overtime, so we use 2. Output for each employee their pay and also output the total number of employees processed and the average pay computed. 2. Examine the file students.txt that you downloaded at the start of the lab. Each row of this file contains a student’s first name, last name, major, and 5 test scores. Write a script that uses a while read statement to input all of the data, line by line, compute the average test score and then assign a letter grade (see the logic on page 15 of the text). The 5th test is worth double (you should divide by 6 instead of 5 since test 5 is worth twice as much). Output for each student, the student’s last name, major and letter grade. Additionally, sum up the number of students who passed (got at least a D or higher) and the number of students who failed. When you run your script, remember to redirect input from students.txt. 3. Write a script that receives a parameter of a major and uses a while read statement to input the data from the student.txt file. Output a list of all students who are of that major and output the number of students found. For instance, you might call this with ./script16 CSC

Paper For Above instruction

The series of shell scripting assignments presented in these labs encapsulate fundamental and advanced scripting techniques essential for automating tasks and managing system resources efficiently in a Unix/Linux environment. These exercises cover a broad spectrum of scripting skills, including control structures, input/output processing, string manipulation, arithmetics, and the use of functions and case statements that make scripts adaptable and robust.

Payroll Calculation Script

Creating a payroll calculator involves reading employee data from a file, processing each employee's hours and wages, and calculating their pay based on an overtime rule. The script reads each line of the employees.txt file, which contains the last name, hours worked, and wages for each employee. Using an if-then-else statement, the script determines whether the employee has worked overtime (more than 40 hours). If so, it computes the pay by multiplying 40 hours by their wages, plus double the wages for each overtime hour beyond 40. Otherwise, it simply multiplies hours by wages. The script maintains counters for total employees processed and the sum of all wages for computing an average. This approach ensures clear, logical calculation and output of individual salaries, total headcount, and average pay, demonstrating control flow and arithmetic calculations.

Student Grade and Performance Analysis

The second task involves reading student records from students.txt, each record including personal and academic data. The script uses a while read loop to process each line, calculating an average test score that counts the fifth test as double. It assigns a letter grade based on the computed average, following predefined grading criteria. The script also tracks the number of students passing (with a minimum grade of D) and failing, demonstrating conditional logic and counters. This task emphasizes string processing, file input handling, and conditional assessments, which are vital in scripting for data analysis and reporting.

Major-specific Student Listing

This task filters students based on their majors. The script takes a major as a parameter and reads student data using a while loop, outputting only the students matching the specified major. It also counts the number of students found, illustrating parameter handling, conditional filtering, and output formatting. Such scripts are useful in managing large datasets and implementing dynamic searches.

Permission String Conversion

Manipulating file permissions involves extracting permission strings using ls and awk, then examining individual characters to convert symbolic permissions into their numeric comparable form. The script iterates over the list of files/directories passed as parameters, retrieves each permission string, and processes characters in the permission bits to calculate numeric permissions, mimicking the conversion from symbolic to octal format. This demonstrates string slicing, conditional checks, and arithmetic operations in shell scripting, foundational for automating file and permission management tasks.

Parameter Analysis and Classification

This component involves analyzing a list of parameters passed to a script, categorizing each based on initial character type, and tallying totals for capital letters, lowercase letters, digits, and other characters. The script uses case statements, character tests, and counters, showcasing control flow, string evaluation, and basic regular expression-like logic.

Numerical Input Statistics

For numerical data collection, a script prompts users repeatedly for positive numbers, ending on negative input. These inputs are stored in an array. The script then uses a for loop to compute the sum, average, maximum, and minimum values in the array. This task solidifies understanding of array handling, looping constructs, and statistical calculations within shell scripting.

Palindrome Detection

The process of palindrome detection requires input string analysis, comparing mirrored characters moving towards the center. A function encapsulates this logic, enhancing reusability. The script iterates through a list of strings, calls the function for each, and reports whether each string is a palindrome, exemplifying string manipulation, loop control, and function definition.

Function-based Palindrome Checker and Batch Testing

Extending the previous palindrome logic into functions allows for modular code reuse. The script defines a function which checks if a string is a palindrome, and then runs multiple strings through this function, outputting results accordingly. This promotes good programming practices and code modularity in shell scripts.

Service Control with Case Statements

Finally, simulating a service control script similar to /etc/init.d/atd involves writing a script with a case statement that reacts to various commands: hello, start, stop, help, etc. Based on user input, it calls functions or outputs messages, demonstrating control flow, parameter validation, and functional scripting. This is particularly useful for sysadmin scripts or custom command interfaces within Unix/Linux systems.

Conclusion

Overall, these lab exercises exemplify the versatility and power of shell scripting in automating routine tasks, processing data, managing files and permissions, and controlling system services. Mastering these techniques forms a vital part of any system administrator's or developer’s toolkit, enhancing efficiency and ensuring repeatability of administrative processes.

References

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