CSE 303 Midterm, February 11, 2009 Page 1 of 8 CSE 303 Midterm Exam February 11, 2009 Name ______________________________________ The exam is closed book, except that you may have a single page of hand‐written notes for reference. If you don’t remember the details of how a specific function or command works (parameter lists, whether an error is indicated by a non‐zero return code or null pointer, etc.), write down the assumptions you need to make and as long as they’re reasonable you’re ok. Please wait to turn the page until everyone has their exam and you have been told to begin. If you have questions during the exam, raise your hand and someone will come to you. Don’t leave your seat. Advice: The solutions to many of the problems are quite short. Don’t be alarmed if there is a lot more room on the page than you actually need for your answer. Also, there may be more than one correct answer to a problem – any of them will be fine as a solution. More gratuitous advice: Be sure to get to all the questions. If you find you are spending a lot of time on a question, move on and try other ones, then come back to the question that was taking the time. 1 / 15 2 / 12 3 / 17 4 / 14 5 / 14 6 / 12 7 / 16 Total / 100 CSE 303 Midterm, February 11, 2009 Page 2 of 8 Question 1. (15 points) Write regular expressions that could be used with grep to to find lines in a file that contain strings with the following patterns. (a) All lines that begin with an upper‐case letter (‘A’ through ‘Z’). (b) All lines containing at least two adjacent digit characters (i.e., 17, 01, 42, 33, 00, etc.). (c) All lines containing six‐character sequences that form a palindrome (i.e., six characters that are the same forward and backwards like “pullup” or “123321” or “ah!!ha”). CSE 303 Midterm, February 11, 2009 Page 3 of 8 Question 2. (12 points) (a) Write a Unix command line (not a shell script) that will print the number of files and directories in the current directory. It should not count files and directories whose names begin with a dot (“.”). The command should just print a single number. (b) Suppose we have a long text file named story.txt. Write a Unix command line (not a shell script) that will display the first few lines of story.txt in the terminal window (i.e., at least the first 5 or 6 lines of the file, but no more than will fit in the window.) The output does not need to completely fill the terminal window, but it must contain the first few lines. CSE 303 Midterm, February 11, 2009 Page 4 of 8 Question 3. (17 points) Give the code for a bash script that deletes files containing more than a given number of bytes. Suppose that the script arguments are named sz, f1, f2, f3, ..., fn. Argument sz is the size (number of bytes) and arguments f1 through fn are the file names. The script should behave as follows: • If no arguments are given (i.e., sz is missing,) the script should write an error message to stderr and exit with a non‐zero exit status. • If at least the first argument (sz) is present, the script should process each of the file arguments f1 through fn in turn. For each file argument, o If the file does not exist or is not a regular file, then ignore that argume nt and continue processing with the next file argument. Do not print any messages. o If the file does exist and is a regular file (i.e., not a directory or some other kind of special file), then if it contains more than sz bytes it should be deleted. If there are no file arguments (i.e., only sz is present), the script should terminate without doing anything further. Hint: wc –c, bash test condition -f. CSE 303 Midterm, February 11, 2009 Page 5 of 8 Question 4. (14 points) A small business keeps their employee address book in a plain text file. Each line in the file contains information about one employee. The information on each line has three fields separated by exclamation marks (!). The fields contain the employee name, office number (building and room), and phone number. For example: Paul Allen!Sieg 134!5‐3425 Susan Sieg!CSE 403!555‐1212 Wilma Flintstone!Sieg 505!3‐5367 Fred Flintstone!CSE 555!3‐7452 Alan Turning!CSE 705!44‐0‐1908‐640404 Write a short shell script that will copy the names and phone numbers of people in a particular building to stdout. The script has two arguments: the first is the name of the text file containing the information in the format described above; the second is the building name. For example, if the first argument to the script is name of a file containing the above data, and the second argument is the string Sieg, the script should produce the following output: Paul Allen 5‐3425 Wilma Flintstone 3‐5367 These are the only two entries in the original file with offices in Sieg. (Note that Susan Sieg’s office is in the CSE building, so her name and phone number do not appear in the output.) Your script should print the message “wrong number of arguments” and exit with a non‐zero exit status if it is not given exactly two arguments. You do not need to check for additional errors: assume that the input file exists and can be read, etc., if the correct number of arguments is given. If the building (argument 2) does not exactly match a building name in the file (argument 1) then the script should produce no output. Hints: sed, grep; a pipeline might be useful. CSE 303 Midterm, February 11, 2009 Page 6 of 8 Question 5. (14 points) Consider the following drawing Stack Heap Complete the definition of function puzzle below so that it creates the above pointer structure, including allocating both ints on the heap and arranging the pointers as shown. (And yes, this diagram does display a memory leak.) void puzzle { int * x; int * y; } x y int: 2 int: 3 CSE 303 Midterm, February 11, 2009 Page 7 of 8 Question 6. (12 points) What does the following program print when it is executed? It does compile and execute successfully without errors. Suggestion: draw a diagram of what happens during execution. That should help you answer the question, and could help us award partial credit if your answer isn’t quite right. #include <stdio.h> #include <string.h> int main(int argc, char
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