Unix Systems Programming: Lab 2

README

1. If you are not in our course email list, please subscribe to the cspp51081 email list here:  http://mailman.cs.uchicago.edu/mailman/listinfo/cspp51081
2. Please start this lab as earlier as possible
3. Before starting, please review lecture 2 notes and read Effective awk Programming, 3rd ed., by Arnold Robbins, available online
4. Turn the lab assignment in by email to the grader by the due date above.
5. Make sure you have read the Homework Style Guidelines for submission.
   

LAB 2

1. Consider the file normal.precip.txt. It contains the average amount of rainfall over a 30 year period for about 275 cities in North America. The first line of the file is a header, which tells you what each column contains. Basically, each line contains a city name, the state the city is in, and then average rainfall amounts from January through December, and then an annual average for all months. The file is TAB delimited. QUESTION: What is the total average amount of rainfall, in inches, for the month of January, for the following states: California (CA), Texas (TX), Alaska (AK). I want individual totalized averages for each of the above states for the month of January. As a check on your algorithm, note that the totalized average rainfall for California (CA) for the month of February over the same period was 2.65067. This was derived by adding the rainfall values together for all cities in California for the month of February, and simply taking their average.

   Please use Awk programming to implement above procedure. There are several steps for this lab:

   1. Figure out the regular expression that will match all the valid chunks of the form described above. Mark has provided a very useful program to help with this process called showmatch that can be used in the following manner:

      hangao@gawaine:CSPP51081% echo "FOO8AB10BAR" | /home/mark/pub/51081/showmatch '[0-9]AB[0-9]'
      FOO8AB10BAR
       ^^^^
      hangao@gawaine:CSPP51081%
      

      The matched portion of the string is returned with carrot characters underneath. This will help you understand how "gawk" works.
   2. If a question is about California, notice that a mere grep of /CA/ will include:

      WINNEMUCCA, NV
      POCATELLO, ID
      

      Probably NOT what you wanted. The shell script "showmatch" maybe help you debug in this regard.
   3. Use "gawk" to integrate the patterns and actions we described above.

    2.   Build Static and Shared Libraries using a Makefile

• Read "make and Makefile" session in Chaper 10 of BLP textbook if you're using that text.  Certainly refer to the online GNU documentation for GNU make .
• Write 3 very simple c source files: hello.c, here.c, bye.c, mylib.h . In hello.c, a function should print out "Hello!"; in here.c , another function should print out "I am here!"; and yet another function should print out "Bye bye!" in bye.c. So, actually, in each code file, there is only one C printf statement. mylib.h should include prototypes for the 3 functions you will be writing.
• Write a main.c to call above 3 functions so that the result should display like following
  "Hello!"
  "I am here!"
  "Bye bye!"
  Please note there is no C printf statement in main.c;
• Read and understand this makefile first and write your own Makefile called Makefile1 to compile them and build a static lib called mylib.a, comprised of hello.c, here.c, and bye.c (but NOT main.c).
• Review "shared libraries naming structure" and "building a shared library" in lecture 3.
• Read and understand this makefile first and write your own makefile called Makefile2 to compile them and build a shared lib with the soname of libmylib.so.5.  Make the minor version .1 and the release .10.  This will mean your actual shared library file will be named "libmylib.so.5.1.10" with .so links set accordingly.
• Note that the two makefiles actually build separate libraries based on the same source code files, one static, the other shared.
  

MARKS DISTRIBUTION

1. Excercise 1:
   
   • 7 points: gawk script
   • 3 points: correct answer as generated by the gawk script
   • 1 points: correct answer in the submitted file
2. Excercise 2:
• 11 points: correct libraries
3. Correct Submission:


• 3 points: Lab submitted as given in the instructions with names on top of files and proper format.

Total Marks: 25

HINTS

Take it slowly and complete each portion of the homework before working on the next as each step depends upon the correct solution to the last. If you think you have the right answer for a step but the test is still failing, mail the list. If you are having any questions at all, mail the list.