LAB 8 ─ File I/O, and UNIX Commands

EECS 2031 Page 1 of 2
LAB 8 ─ File I/O, and UNIX Commands
Problem A – File I/O
1. Specification
Write a C program to input student records from a file. Each entry of the input file has the following
format:
[First name] [Last name] [Assignment 1 mark] [Assignment 2 mark]
Copy the input data to an output file, and add one more field that records the average of the two
assignment marks. So each entry of the output file has the following format:
[First name] [Last name] [Assignment 1 mark] [Assignment 2 mark] [Average mark]
2. Implementation
• The program to be submitted is named marks.c. Use the given template marks.c and fill in
your code. Submit only file marks.c.
• To compile the program, use the following command: cc marks.c –o marks
• The file names are input as command line arguments. File names are less than 30 characters long.
• Sometimes users may forget the command syntax and they may type only the command “marks”,
or enter only one file name. In that case, display the following reminder message on the standard
output:
Usage: marks [input_file] [output_file]
• Assignment marks are integers. Average marks are of type float. Output the average marks with
one decimal digit.
• If a file cannot be opened for read or write, display an error message and exit the program using
exit(1).
• Use fscanf() to read from the input file and fprintf() to write to the output file.
• You may define your own variables inside function main(), and implement your own function(s)
in file marks.c.
• Assume that students’ names and marks to be input are valid and no error checking is required.
3. Sample Inputs/Outputs
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See file marks_exe.txt for a snapshot of program execution, and contents of the sample input and
output files.
Common Notes
• Complete the header in file marks.c with your student and contact information.
Problem B – UNIX Commands
See the next page.
Lab 8 - UNIX Commands
1. The echo command takes a line that you type and repeats it back on the screen. Redirect your input line to
a file named myFile.
2. Use the echo command to input 5 more lines and redirect them to file myFile, which will contain a total of
6 lines of text.
3. Using the commands who, who am i, and date, append to file myFile the outputs of the above commands.
4. Suppose myFile is in your working directory. Specify the command(s) you would use to do the following:
a. Give everyone permission to read myFile; do not change any other privileges.
b. Permit the owner (you) and group members to read and write the file; remove all privileges from
everyone else.
c. Remove writing privileges from everyone but the owner.
d. Give the owner and group members permission to execute myFile, while giving the owner sole
permission to read and write the file.
5. Suppose you have a directory named myStuff in your working directory. Specify the command(s) you
would use to do the following:
a. Give everyone permission to list files in myStuff; do not change any other privileges.
b. Permit the owner and group members to list, remove, or add files; remove all privileges from
everyone else.
c. Remove writing privileges from everyone but the owner.
d. Give the owner and group members permission to execute myStuff, while giving the owner sole
permission to read and write the directory.
6. Create a set of text files and name them backgammon, backpacking, baseball, boxing, biking, chess,
fencing, blackjack, groupA, groupB, groupX, groupY.
a. How would you use cat to show the contents of the files ending in ing?
b. How would you list any files containg x or X in the file names?
c. How would you show the contents of files with names containing o?
d. How would you show the contents of the files backgammon, backpacking and blackjack using just
one command?
e. How would you copy the contents of all 3 files backgammon, backpacking and blackjack to a file
named all3 using just one command?
7. Given the file phone_book.txt, specify the command(s) you would use to do the following:
a. Display entries of people whose names contain pattern alex, case-insensitive. (The output should be
the entries of alex johnson and Alexander Smith.)
b. Count the number of people whose area code is 905. Display just the count (not the entries).
c. Display the entries of the babysitters.
d. Count the number of friends whose names are in phone_book.txt. Display just the count (not the
entries).
Save your commands in a file named lab7_unix.txt containing the following header and submit file lab7_unix.txt.
# EECS 2031 - Lab 8
# Filename: lab8_unix.txt
# Author: Last name, first name
# Email: Your email address
# Login ID: Your login ID