To gain experience working on a collaborative project, developing the first version of tools that will be used together in various combinations in an interconnected manner.

In UNIX, everything is a file.

In C, we've relied on this basic operational rule everytime we perform input and output. There are three files automatically opened for us each time we run a program. They are:

• STDIN - where you get input from (by default, your keyboard)
• STDOUT - where your output goes (by default, your terminal)
• STDERR - where any error messages go (by default, your terminal)

Because everything is a file, manipulations can more easily be performed.

A facility that UNIX provides is that of the pipe (the usage of the '|' character), which can string together seemingly separate commands, allowing the output of one to become the input to the next (and so on…)

Examples of the pipe can be seen here, such as by counting the number of lines in a file:

lab46:~$ cat /etc/motd | wc -l
19
lab46:~$ 

cat will display data (the file's contents), wc counts data… so we put the two together, creating something that is unique in functionality.

Your task is to implement three assigned programs in the pipemath-fall2014 project repository you'll have cloned.

The three programs belong to one of each of these categories:

In src/numbers/, are files containing code that will display the numeric value of their namesake to STDOUT.

For example, here is the code to src/numbers/one.c:

1

//////////////////////////////////////////////////////////////////////
//
// one.c     - program that displays the number '1' to STDOUT. It does
//             not take any input.
//
// Written By: Matthew Haas <wedge@lab46.corning-cc.edu>
// Compile:    run 'Make' from the project's base directory
// Execute:    change into project 'bin/' or add project bin/ to your
//             PATH
//
// Sample run:
//
//    lab46:~/src/pipemath-fall2014/bin$ ./one
//    1
//    lab46:~/src/pipemath-fall2014/bin$ 
//
#include <stdio.h>
#include <stdlib.h>
 
int main(int argc, char **argv)
{
    fprintf(stdout, "1\n");
    return (0);
}

It may seem nonsensically simple and straightforward, but again- a part of this project is to generate activity on the repository, and this will do just that.

In src/bases/, are files containing code that will take input (from STDIN), and convert that input (assume base 10 for this project) to the indicated base.

For example, here is the code to src/bases/tobase8.c:

1

//////////////////////////////////////////////////////////////////////
//
// tobase8.c - program that displays the number input from STDIN in
//             a base 8 representation to STDOUT.
//
// Written By: Matthew Haas <wedge@lab46.corning-cc.edu>
// Compile:    run 'Make' from the project's base directory
// Execute:    change into project 'bin/' or add project bin/ to
//             your PATH
//
// Sample run:
//
//    lab46:~/src/pipemath-fall2014/bin$ ./nine | ./plus 4 | ./tobase8
//    15
//    lab46:~/src/pipemath-fall2014/bin$ 
//
#include <stdio.h>
#include <stdlib.h>
 
int main(int argc, char **argv)
{
    int value;
 
    fscanf (stdin,  "%d",  &value);
 
    fprintf(stdout, "%o\n", value);
 
    return(0);
}

You'll notice usage examples are given in the comment banner up top.

You'll also notice I took the liberty of doing all the “easy” ones (base 8, base 10, base 16).

What makes this project particularly fun is how we can perform fairly simple mathematical operations on the information we generate with all these tools.

In src/maths/, are files containing code that will take input (from STDIN), and will need to take in information from the command-line as another piece of information, and do the necessary processing to generate the correct result to STDOUT.

For example, here is the code to src/maths/increment.c:

1

//////////////////////////////////////////////////////////////////////
//
// increment.c - program that accepts input from STDIN, and displays 
//               the result to STDOUT.
//
// Written By:   Matthew Haas <wedge@lab46.corning-cc.edu>
// Compile:      run 'Make' from the project's base directory
// Execute:      change into project 'bin/' or add project bin/ to
//               your PATH
//
// Sample run:
//
//    lab46:~/src/pipemath-fall2014/bin$ ./three | ./increment
//    4
//    lab46:~/src/pipemath-fall2014/bin$ 
//
#include <stdio.h>
#include <stdlib.h>
 
int main(int argc, char **argv)
{
    int input;
 
    fscanf (stdin,  "%d",   &input);
 
    fprintf(stdout, "%d\n", (input+1));
 
    return(0);
}

Both increment and decrement are exceptions here- they are unary operations, so they have no present need to process command-line arguments. But all the other operations are binary, so they do.

There are 8 math operations in need of implementing, they are:

• divideby (take input and divide it by the command-line argument)
• log (1st command-line argument is the 'base', input is x – b^y = x)
• minus (take input and subtract the command-line argument from it)
• modulus (take input and obtain the remainder)
• multiplyby (take input and multiply by command-line argument)
• plus (take input and add to command-line argument)
• toplaces (not really 'math', but format the output to provide leading zeros according to argument)
• topowerof (take input and raise it to the power of the command-line argument)

Now, there are a few ground rules we need to keep in mind:

• you are to use only the basic math operators (+, -, *, /, %)
  • NO using the math library!
• you are to do your own work.
  • these programs are very similar, so be careful not to give away the secrets.
• you may use C library functions to convert the command-line argument to integer data (atoi(3))
• you may assume that only correct information ever gets provided
  • you do not need to worry about checking for incorrect data
• you DO need to check, where appropriate, for the existence of a command-line argument
  • should a required argument be missing, you SHOULD:
    • display an error (to STDERR)
    • cause the program to exit(3)

To successfully complete this project, the following criteria must be met:

• Code must compile cleanly (no warnings or errors)
• Assigned programs must correctly handle input according to project requirements
• Assigned programs must correctly perform processing according to project requirements
• Assigned programs must correctly generate output according to project requirements
• Code must be nicely and consistently indented (you may use the indent tool)
• Code must be commented
  • have a properly filled-out comment banner at the top
  • have at least 20% of your program consist of //-style descriptive comments
• Utilize mercurial version control to perform repository transactions
  • Appropriately resolve any conflicts, and obtain new changes by doing a pull/update as needed
  • Commit and Push at least 3 changes (your assigned programs, minimum of 1 commit per program)
    • This doubles as your assignment submission for this project