Add EC2 list instances example

example/service/ec2/instancesbyRegion/README.md

@@ -0,0 +1,32 @@
+
+# Example  Fetch By region
+
+This is an example using the AWS SDK for Go to list ec2 instances instance state By different region . By default it fetch all running and stopped instance 
+
+
+# Usage
+
+
+```sh
+# To fetch the stopped instance of all region use below:
+./filter_ec2_by_region --state running --state stopped
+
+# To fetch the stopped and running instance  for  region us-west-1 and eu-west-1 use below:
+./filter_ec2_by_region --state running --state stopped --region us-west-1 --region=eu-west-1
+```
+
+## Sample Output
+
+```
+Fetching instace details  for region: ap-south-1 with criteria:  [running][stopped]**
+ printing instance details.....
+instance id i-************
+current State stopped
+done for region ap-south-1 ****
+
+
+
+Fetching instace details  for region: eu-west-2 with criteria:  [running][stopped]**
+ There is no instance for the for region eu-west-2 with the matching Criteria: [running][stopped]
+done for region eu-west-2 ****
+```

example/service/ec2/instancesbyRegion/instancesByRegion.go

@@ -0,0 +1,137 @@
+// +build example
+
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/aws/aws-sdk-go/aws"
+	"github.com/aws/aws-sdk-go/aws/session"
+	"github.com/aws/aws-sdk-go/service/ec2"
+)
+
+// Prints a list of instances for each region. If no regions are provided
+// all regions will be searched. The state is required.
+//
+// Will use the AWS SDK for Go's default credential chain and region. You can
+// specify the region with the AWS_REGION environment variable.
+//
+// Usage: instancesByRegion -state <value> [-state val...] [-region region...]
+func main() {
+	states, regions := parseArguments()
+
+	if len(states) == 0 {
+		fmt.Fprintf(os.Stderr, "error: %v\n", usage())
+		os.Exit(1)
+	}
+	instanceCriteria := " "
+	for _, state := range states {
+		instanceCriteria += "[" + state + "]"
+	}
+
+	if len(regions) == 0 {
+		var err error
+		regions, err = fetchRegion()
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "error: %v\n", err)
+			os.Exit(1)
+		}
+	}
+
+	for _, region := range regions {
+		sess := session.Must(session.NewSession(&aws.Config{
+			Region: aws.String(region),
+		}))
+
+		ec2Svc := ec2.New(sess)
+		params := &ec2.DescribeInstancesInput{
+			Filters: []*ec2.Filter{
+				&ec2.Filter{
+					Name:   aws.String("instance-state-name"),
+					Values: aws.StringSlice(states),
+				},
+			},
+		}
+
+		result, err := ec2Svc.DescribeInstances(params)
+		if err != nil {
+			fmt.Println("Error", err)
+		} else {
+			fmt.Printf("\n\n\nFetching instace details  for region: %s with criteria: %s**\n ", region, instanceCriteria)
+			if len(result.Reservations) == 0 {
+				fmt.Printf("There is no instance for the for region %s with the matching Criteria:%s  \n", region, instanceCriteria)
+			}
+			for _, reservation := range result.Reservations {
+
+				fmt.Println("printing instance details.....")
+				for _, instance := range reservation.Instances {
+					fmt.Println("instance id " + *instance.InstanceId)
+					fmt.Println("current State " + *instance.State.Name)
+				}
+			}
+			fmt.Printf("done for region %s **** \n", region)
+		}
+	}
+}
+
+func fetchRegion() ([]string, error) {
+	awsSession := session.Must(session.NewSession(&aws.Config{}))
+
+	svc := ec2.New(awsSession)
+	awsRegions, err := svc.DescribeRegions(&ec2.DescribeRegionsInput{})
+	if err != nil {
+		return nil, err
+	}
+
+	regions := make([]string, 0, len(awsRegions.Regions))
+	for _, region := range awsRegions.Regions {
+		regions = append(regions, *region.RegionName)
+	}
+
+	return regions, nil
+}
+
+type flagArgs []string
+
+func (a flagArgs) String() string {
+	return strings.Join(a.Args(), ",")
+}
+
+func (a *flagArgs) Set(value string) error {
+	*a = append(*a, value)
+	return nil
+}
+func (a flagArgs) Args() []string {
+	return []string(a)
+}
+
+func parseArguments() (states []string, regions []string) {
+	var stateArgs, regionArgs flagArgs
+
+	flag.Var(&stateArgs, "state", "state list")
+	flag.Var(&regionArgs, "region", "region list")
+	flag.Parse()
+
+	if flag.NFlag() != 0 {
+		states = append([]string{}, stateArgs.Args()...)
+		regions = append([]string{}, regionArgs.Args()...)
+	}
+
+	return states, regions
+}
+
+func usage() string {
+	return `
+
+Missing mandatory flag 'state'. Please use like below  Example:
+
+To fetch the stopped instance of all region use below:
+	./filter_ec2_by_region -state running -state stopped
+
+To fetch the stopped and running instance  for  region us-west-1 and eu-west-1 use below:
+	./filter_ec2_by_region -state running -state stopped -region us-west-1 -region=eu-west-1
+`
+}