This challenge is to build your version of the Unix command line tool wc!
The Unix command line tools are a great metaphor for good software engineering and they follow the Unix Philosophies of:
- Writing simple parts connected by clean interfaces - each tool does just one thing and provides a simple CLI that handles text input from either files or file streams.
- Design programs to be connected to other programs - each tool can be easily connected to other tools to create incredibly powerful compositions.
Following these philosophies has made the simple Unix command line tools some of the most widely used software engineering tools - allowing us to create very complex text data processing pipelines from simple command line tools. There’s even a Coursera course on Linux and Bash for Data Engineering.
You can read more about Unix Philosophy in the excellent book The Art of Unix Programming.
The functional requirements for wc are concisely described by its man page - give it a go in your local terminal now:
man wcThe TL/DR version is: wc – word, line, character, and byte count.
Like all good software engineering, we’re zero-indexed! In this step, you’re going to set your environment up ready to begin developing and testing your solution.
I’ll leave you to set up your IDE/editor of choice and programming language of choice. After that here’s what I’d like you to do to be ready to test your solution.
Download this text and save it as test.txt.
In this step, your goal is to write a simple version of wc, let’s call it ccwc (cc for Coding Challenges) that takes the command line option -c and outputs the number of bytes in a file.
If you’ve done it right your output should match this:
>ccwc -c test.txt
342190 test.txtIf it doesn’t, check your code, fix any bugs, and try again. If it does, congratulations! On to…
In this step, your goal is to support the command line option -l that outputs the number of lines in a file.
If you’ve done it right your output should match this:
>ccwc -l test.txt
7145 test.txtIf it doesn’t, check your code, fix any bugs, and try again. If it does, congratulations! On to…
In this step, your goal is to support the command line option -w that outputs the number of words in a file. If you’ve done it right your output should match this:
>ccwc -w test.txt
58164 test.txtIf it doesn’t, check your code, fix any bugs, and try again. If it does, congratulations! On to…
In this step, your goal is to support the command line option -m that outputs the number of characters in a file. If the current locale does not support multibyte characters this will match the -c option.
You can learn more about programming for locales here
For this one your answer will depend on your locale, so if can, use wc itself and compare the output to your solution:
>wc -m test.txt
339292 test.txt
>ccwc -m test.txt
339292 test.txtIf it doesn’t, check your code, fix any bugs, and try again. If it does, congratulations! On to…
In this step your goal is to support the default option - i.e. no options are provided, which is equivalent to the -c, -l and -w options. If you’ve done it right your output should match this:
>ccwc test.txt
7145 58164 342190 test.txtIf it doesn’t, check your code, fix any bugs, and try again. If it does, congratulations! On to…
In this step, your goal is to support being able to read from standard input if no filename is specified. If you’ve done it right your output should match this:
>cat test.txt | ccwc -l
7145If it doesn’t, check your code, fix any bugs, and try again. If it does, congratulations! You’ve done it, pat yourself on the back, job well done!