Suport arbitrary path for ec2-metadata.

ec2-metadata does not support all meta-data listed in the document. [0]

Let's support such meta-data with a generic option, --path.

It can be specified multiple times and used with other options:

  $ ./ec2-metadata --path events/maintenance/scheduled \
    --path meta-data/identity-credentials/ec2/security-credentials/ec2-instance \
    --region
  latest/meta-data/events/maintenance/scheduled: []
  latest/meta-data/identity-credentials/ec2/security-credentials/ec2-instance: {
    "Code" : "Success",
    "LastUpdated" : "2025-04-07T04:58:06Z",
    "Type" : "AWS-HMAC",
    ...
    "Expiration" : "2025-04-07T11:01:19Z"
  }
  region: ap-northeast-1

Also, it can be used to fetch non-latest meta-data and dynamic data:

  $ ./ec2-metadata --path /
  /: 1.0
  2007-01-19
  ...

  $ ./ec2-metadata --path /2009-04-04/dynamic
  /2009-04-04/dynamic: instance-identity/

Link: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-instance-metadata.html #[0]
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>

Author: q2ven

doc/ec2-metadata.8

@@ -119,6 +119,9 @@ Print EC2 resource tags if permitted in EC2 Instance Metadata Options.
 .B \-\-quiet
 Don't print metadata keys
 .TP
+.B \-\-path
+Show metadata information from the specified path.  Can be specified multiple times.
+.TP
 .B \-h, \-\-help
 Show summary of options.
 .SH SEE ALSO

ec2-metadata

@@ -8,7 +8,7 @@
 
 function print_help()
 {
-echo "ec2-metadata v0.1.4
+echo "ec2-metadata v0.1.5
 Use to retrieve EC2 instance metadata from within a running EC2 instance. 
 e.g. to retrieve instance id: ec2-metadata -i
 		 to retrieve ami id: ec2-metadata -a
@@ -41,11 +41,13 @@ Options:
 -s/--security-groups      Names of the security groups the instance is launched in. Only available if supplied at instance launch time
 -d/--user-data            User-supplied data.Only available if supplied at instance launch time.
 -g/--tags                 Tags assigned to this instance.
---quiet                   Suppress tag keys from the output."
+--quiet                   Suppress tag keys from the output.
+--path                    Show metadata information from the specified path.  Can be specified multiple times."
 }
 
 METADATA_BASEURL="http://169.254.169.254"
 METADATA_TOKEN_PATH="latest/api/token"
+METADATA_VERSION="latest"
 QUIET=""
 
 function set_imds_token()
@@ -63,7 +65,7 @@ function set_imds_token()
 function get_meta()
 {
 	local imds_out
-	imds_out=$(curl -s -q -H "X-aws-ec2-metadata-token:${IMDS_TOKEN}" -f ${METADATA_BASEURL}/latest/${1})
+	imds_out=$(curl -s -q -H "X-aws-ec2-metadata-token:${IMDS_TOKEN}" -f ${METADATA_BASEURL}/${METADATA_VERSION}/${1})
 	echo -n "${imds_out}"
 }
 
@@ -156,6 +158,27 @@ function print_all()
 	print_tags
 }
 
+function print_path()
+{
+	local path
+
+	path=$(echo "$1" | sed 's/\/\+/\//g')
+
+	if [[ ! "$path" =~ (^/$|^/?(1\.0|[0-9]{4}-[0-9]{2}-[0-9]{2}|latest)) ]]; then
+		if [[ "$path" =~ ^/?(dynamic|meta-data) ]]; then
+			path="latest/$path"
+		else
+			path="latest/meta-data/$path"
+		fi
+	fi
+
+	path=$(echo "$path" | sed 's/\/\+/\//g')
+
+	METADATA_VERSION=""
+	print_normal_metric "$path" "$path"
+	METADATA_VERSION="latest"
+}
+
 #check if run inside an EC2 instance
 set_imds_token
 
@@ -165,11 +188,12 @@ if [ "$#" -eq 0 ]; then
 fi
 
 declare -a actions
+declare -a paths
 shortopts=almnbithokzPcpvuresdgR
 longopts=(ami-id ami-launch-index ami-manifest-path ancestor-ami-ids block-device-mapping
           instance-id instance-type local-hostname local-ipv4 kernel-id availability-zone
           partition product-codes public-hostname public-ipv4 public-keys ramdisk-id
-          reservation-id security-groups user-data tags region help all quiet)
+          reservation-id security-groups user-data tags region help all quiet path:)
 
 oldIFS="$IFS"
 IFS=,
@@ -192,6 +216,11 @@ while true; do
         --quiet)
             QUIET=1 ; shift
             ;;
+        --path)
+            actions+=("$1")
+            paths+=("$2")
+            shift 2
+            ;;
         --)
             shift ; break
             ;;
@@ -232,6 +261,7 @@ for action in "${actions[@]}"; do
 	    -s | --security-groups )       print_normal_metric security-groups meta-data/security-groups ;;
 	    -d | --user-data )             print_normal_metric user-data user-data ;;
 	    -g | --tags )                  print_tags ;;
+	    --path )                       print_path "${paths[0]}"; paths=("${paths[@]:1}") ;;
 	    --all )                        print_all; exit ;;
 	esac
 	shift