Add printenv

README.md

@@ -14,3 +14,4 @@ Implemeted utilities:
  * `dirname`
  * `basename`
  * `echo`
+ * `printenv`

printenv/printenv.go

@@ -0,0 +1,32 @@
+package main
+
+import (
+	"fmt"
+	"os"
+)
+
+func printStrings(strings []string) {
+	for _, str := range strings {
+		fmt.Println(str)
+	}
+}
+
+func main() {
+	if len(os.Args) == 1 {
+		printStrings(os.Environ())
+		os.Exit(0)
+	}
+
+	exitCode := 0
+	envVars := []string{}
+	for _, key := range os.Args[1:] {
+		val, present := os.LookupEnv(key)
+		if present {
+			envVars = append(envVars, val)
+		} else {
+			exitCode = 1
+		}
+	}
+	printStrings(envVars)
+	os.Exit(exitCode)
+}