add: new input scanning exercises

23-input-scanning/exercises/04-grep/main.go

@@ -0,0 +1,29 @@
+package main
+
+// ---------------------------------------------------------
+// EXERCISE: Grep Clone
+//
+//  Create a grep clone. grep is a command-line utility for
+//  searching plain-text data for lines that match a specific
+//  pattern.
+//
+//  1. Feed the shakespeare.txt to your program.
+//
+//  2. Accept a command-line argument for the pattern
+//
+//  3. Only print the lines that contains that pattern
+//
+//  4. If no pattern is provided, print all the lines
+//
+//
+// EXPECTED OUTPUT
+//
+//  go run main.go come < shakespeare.txt
+//
+//    come night come romeo come thou day in night
+//    come gentle night come loving black-browed night
+//
+// ---------------------------------------------------------
+
+func main() {
+}

23-input-scanning/exercises/04-grep/shakespeare.txt

@@ -0,0 +1,12 @@
+come night come romeo come thou day in night
+for thou wilt lie upon the wings of night
+whiter than new snow on a raven's back
+come gentle night come loving black-browed night
+give me my romeo and when he shall die
+take him and cut him out in little stars
+and he will make the face of heaven so fine
+that all the world will be in love with night
+and pay no worship to the garish sun
+oh i have bought the mansion of love
+but not possessed it and though i am sold
+not yet enjoyed

23-input-scanning/exercises/04-grep/solution/main.go

@@ -0,0 +1,31 @@
+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strings"
+)
+
+func main() {
+	in := bufio.NewScanner(os.Stdin)
+
+	var pattern string
+	if args := os.Args[1:]; len(args) == 1 {
+		pattern = args[0]
+	}
+
+	for in.Scan() {
+		s := in.Text()
+		if strings.Contains(s, pattern) {
+			fmt.Println(s)
+		}
+	}
+}

23-input-scanning/exercises/04-grep/solution/shakespeare.txt

@@ -0,0 +1,12 @@
+come night come romeo come thou day in night
+for thou wilt lie upon the wings of night
+whiter than new snow on a raven's back
+come gentle night come loving black-browed night
+give me my romeo and when he shall die
+take him and cut him out in little stars
+and he will make the face of heaven so fine
+that all the world will be in love with night
+and pay no worship to the garish sun
+oh i have bought the mansion of love
+but not possessed it and though i am sold
+not yet enjoyed