Lab 8: Links, Makefiles, & Character Processing

Objectives

In this lab we will look at tools and techniques to make our job as programmers easier: using symbolic links to share source and header files, and using make to automate compilation of the code. We will use the roman number program as our example. You will then get a chance to modify the roman program, and to work on another small character based program. You should begin by creating a new directory called Lab8 in your EE160/Labs directory (which you have created in previous labs). All of the program files you write for this lab should be in this Lab8 directory. To begin this lab, the TA will go over the concepts and commands for using symbolic links and makefiles.

Programs

• (5 Points). The roman number program above works correctly, provided the user enters valid roman digits followed by a newline at the prompt. If the user enters an invalid roman digit (even spaces), the programs behaves somewhat reasonably (What does it do?), but we would like to make it better.
  • To do this, you will need access to the files for the roman number program. Instead of everyone in the class copying my files to each of your directory, you will share my files using a symbolic link. To do this, first, copy the makefile from ~ee160/Code.lect/Roman to your Lab8 directory. Then run the command:
    • make links
  • We would like the program to be tolerent of white space (spaces and tabs, and still provide the result if all of the other characters are valid roman digits.
  • If the user enters invalid characters, we would like the function to return 0 as a special value indicating an error instead of a partial result so far. We can use 0 as a special value because there is no Roman number representation for 0 (the Romans didn't understand 0) so 0 would not be returned for normal input. The driver should print an error message when this occurs and let the user try entering another number. You may modify any of the files that you need to, but you will need to break the link and copy the file for those you want to change.
• (5 Points). Compile and run the program found in readcmd.c. This program accepts single letter commands as input and simply prints out the command it read. Any blanks in front of the command are ignored, as are any characters after the command. You should type in input lines like the following to see how it behaves:

            a

               a

               and this is a long line

• One of the things you will notice about this program is that it is not documented with comments for the algorithm or for the functions. Your first task is to document this code. Copy the program into myreadcmd.c, and extend this file to ignores leading tabs as well as leading blanks (or any combinations of blanks and tabs). Now extend the program to have either a semi-colon or a newline character indicate the end of a command. Here's a sample run:

            a   ;    b

            The command is: a

            The command is: b

              a

            The command is: a

• Now extend the program to verify that the command is an upper or lower case letter. It should print an error message if it isn't. Also, verify that the line has a command: if it hits a blank or ; without an intervening command, you should print an error. Here's a sample run:

            a   ;    b

            The command is: a

            The command is: b

              +

            Error: + is not a letter.

            /

            Error: / is not a letter.

            Error: missing command.

            ;    b

            Error: missing command.

            The command is: b

What You Turn In

Use the "grade" command to turn in the all of the source files (.c and .h files) in your Lab8 directory. Your command will look like the following.

If you are in Section 001 use:

           grade -lab8s1,ee160  *.c *.h

If you are in Section 002 use:

           grade -lab8s2,ee160  *.c *.h

If you are in Section 003 use:

           grade -lab8s3,ee160  *.c *.h

If you are in Section 004 use:

           grade -lab8s4,ee160  *.c *.h

NOTE: this command will send in ALL files named with .c and .h extensions in the current directory which are really your files. The grade command will give you a message for files that are links and not submit the files - that is ok, we only want the files which you wrote. You should verify that you turned in things successfully, which you can do with the command (which simply leaves the file names off from the previous command).

           grade -lab8s1,ee160

           OR

           grade -lab8s2,ee160

           OR

           grade -lab8s3,ee160

NOTE: after the files are prepared for grading, you will no longer be able to see your file listing using the above command. NOTE: BE CAREFUL to use the correct form of the grade command given above. If you do not, your files will be sent to the wrong place, and we will not guarantee we will find them for grading.