How to do it...

These steps cover writing and running your application:

1. From your terminal/console application, create a new directory called chapter2/pipes and navigate to that directory.
2. Copy tests from https://github.com/agtorre/go-cookbook/tree/master/chapter2/pipes, or use this as an exercise to write some of your own code!

1. Create a file called pipes.go with the following contents:

        package main

        import (
            "bufio"
            "fmt"
            "io"
            "os"
        )

        // WordCount takes a file and returns a map
        // with each word as a key and it's number of
        // appearances as a value
        func WordCount(f io.Reader) map[string]int {
            result := make(map[string]int)

            // make a scanner to work on the file
            // io.Reader interface
            scanner := bufio.NewScanner(f)
            scanner.Split(bufio.ScanWords)

            for scanner.Scan() {
                result[scanner.Text()]++
            }

            if err := scanner.Err(); err != nil {
                fmt.Fprintln(os.Stderr, "reading input:", err)
            }

            return result
        }

        func main() {
            fmt.Printf("string: number_of_occurrences\n\n")
            for key, value := range WordCount(os.Stdin) {
                fmt.Printf("%s: %d\n", key, value)
            }
        }

1. Run echo "some string" | go run pipes.go.
2. You may also run these:

      go build
      echo "some string" | ./pipes

You should see the following output:

      $ echo "test case" | go run pipes.go
      string: number_of_occurrences

      test: 1
      case: 1

      $ echo "test case test" | go run pipes.go
      string: number_of_occurrences

      test: 2
      case: 1

1. If you copied or wrote your own tests, go up one directory and run go test. Ensure all tests pass.