Unix Tools Assignment

This assignment is unofficial: you don’t have to turn it in and it won’t count toward your grade. If you don’t have a lot of experience with programming-in-the-large in Unix, however, we strongly recommend that you complete it.
                        CSC 254 - Programming Systems

                                September 2023

                            Homework Assignment #0
                             (Not to be turned in)

       The purpose of this assignment is to familiarize you with some of the
  tools you will be using for the assignments this semester.  You may already
  know this stuff, in which case feel free to just skim it.  If not, now's the
  time to learn!

  1.  Undergraduate majors and CS MS students should already have
      accounts on the CS instructional machines.  If you don't, visit
      accounts.csug.rochester.edu and follow the instructions there.
      Learn how to log in, both in person and remotely.  You may also
      want to learn to use an X window server for graphical interaction
      with remote clients.  XQuartz is the standard server for MacOS.
      Free servers for Microsoft Windows (e.g., Cygwin/X) are also widely
      available.

  2.  Try out the "man" command.  At the prompt, type

             man passwd

      You will see the name of the passwd command, the list of possible
      command line options, and a description of what the command and the
      options do.  You will find that almost every command has more
      options than you realized, most of which no one ever uses (try man
      cat!).  Try also the following commands (don't bother reading all
      the details about every option - you won't remember them anyway).

             man less
             man ls
             man od

      You can find out more about the man command (which stands for
      "manual") by typing

             man man

  3.  Write a "hello, world" program in C++.  You can use the following
      code.

             #include <iostream>
             using namespace std;

             int main()
             // this is a comment
             /* this is also
                  a comment */
             {
                   int i;
                   cout << "Hello, world.\n";
                   i = 3;
                   cout << "i = " << i << endl;
                   return 0;
             }

      Use an editor (vim or emacs) to type this into a file named "hello.cc".
      For those not familiar with C++, the #include command tells the
      compiler to read declarations from another file.  The pointy
      brackets around the name tell the compiler to look in a library of
      "standard" declaration files.

  4.  Compile the "hello, world" program using the command

             g++ -v hello.cc

      The -v option (for verbose) shows the name and arguments of each
      program the compiler executes.

  5.  You should now have an executable file "a.out" which you can run by
      simply typing

             ./a.out

  6.  Read the man page for the compiler and find the command-line switches
      that will cause it to save the various intermediate files you saw in
      step 4 above.  Take a look at these files, using 'less' to look at
      text, and 'nm', 'od', or 'objdump' to look at object (machine
      language) files.  You can find out if a file is text or data by
      using the 'file' command with the filename as the argument.

  7.  Type the following lines into a file named "Makefile":

             hello: hello.cc hello.h
                     echo first message
                     @echo another message
                     g++ -o hello hello.cc

      Be warned that the indented lines have to start with a tab character,
      not a series of spaces.  Create a file called "hello.h" with the
      following line in it:

             const int VAL = 3;

      Finally, edit hello.cc and change it so that it reads as follows:

             #include <iostream>
             #include "hello.h"
             using namespace std;

             int main()
             // this is a comment
             /* this is also
                  a comment */
             {
                   int i;
                   cout << "Hello, world.\n";
                   i = VAL;
                   cout << "i = " << i << endl;
                   return 0;
             }

      Type "make" and notice the output.  You should now have a file called
      "hello" which you can run.  Type "make" again and notice that it does
      not recompile hello (because you haven't changed it).

  8.  To see an example of separately compiled source files, type the
      following into a file called "main.cc":

             #include <iostream>
             #include "dumb.h"
             using namespace std;

             int main()
             {
                   cout << "Hello, world.\n";
                   dumb_func(10);
                   return 0;
             }

      and type the following lines into a file called "dumb.cc".

             #include <iostream>
             #include "dumb.h"
             using namespace std;

             void dumb_func(int n)
             {
                   cout << "n = " << n << "\n";
             }

      The header file "dumb.h" should have this line in it:

             void dumb_func(int n);

      Finally, change your Makefile to read as follows:

             .cc.o:
                   g++ -c $*.cc

             hello: main.o dumb.o
                   g++ -o hello main.o dumb.o

             main.o: main.cc dumb.h
             dumb.o: dumb.cc dumb.h

      Now type "make" and observe what happens.  The strange looking new
      rule at the top of the file tells make how to turn an arbitrary .cc
      file into a .o file.  A warning: make has some built-in rules.  If
      you forget to provide the .cc.o rule, make will use its own, which
      may not call g++ the way you expect.

      Change each of the files main.cc, dumb.cc, and dumb.h and run make
      after each change.  Notice that a change to a source file does not
      force recompilation of unrelated source files.

   9. Use gdb to run one of the above programs or one of your own.  You
      should change your Makefile so that it compiles your program with
      the "-g" option, which facilitates debugging.  You can force make
      to use this option automatically by including it in the .cc.o
      rule:

             .cc.o:
                     g++ -c -g $*.cc

      To use gdb type "gdb filename" where filename is the name of the
      executable file.  If you have not used gdb before, type "help" at the
      prompt.  Experiment with setting breakpoints and single-stepping, and
      use the commands "list", "display", "where", and "print".

  10. Tag files contain the source file locations of all function,
      macro, and type definitions used in a programming project.  Most
      editors, including vim and emacs, are able to jump directly to the
      source code location of a function, macro, or type definition, as
      specified in the project's tag file.

      To create tag files, edit Makefile and add the following makefile
      target:

             tags:
                     etags *.cc *.h
                     ctags *.cc *.h

      Now run "make tags" to create tag files for both vim and emacs.
      To use the tags, open hello.cc in your favorite editor, and type
      the appopriate command:

             vim:
                     :ta dumb_func

             emacs:
                     Meta-.
                     dumb_func

      This should take you to the definition of function dumb_func.
      To return to where you came from, type ^t (control-t) in vim, or
      Meta-* in emacs.

  11. Version control (VC) systems are a crucial tool for keeping track
      of the history of changes made to files.  Such systems maintain
      only the diffs between versions, minimizing space requirements.
      They allow you to recover if you accidentally delete a file, or to
      "back out" to a previous version if you decide you don't like your
      recent changes.  They also facilitate logging of notes about your
      changes.  More advanced features mediate concurrent changes by
      multiple members of a team, either via locking or via intelligent
      merging.

      Much of the systems world has converged around the git VC system.
      Unfortunately, git is very complicated.  Other, simpler
      alternatives include rcs (very old, very simple), cvs (built on
      top of rcs, and still pretty old), subversion (svn), bazaar (bzr),
      mercurial (hg), and perforce (p4).

      Documentation for all of these can be found online.
  

Last Change: 20 August 2023 / Michael Scott's email address