Snapshot name bug #59 (#70)

Restrict custom prefix to 20 characters

Author: jacksegal

Diff for: README.md

@@ -68,6 +68,7 @@ Options:
           access to [OPTIONAL].
     -f    gcloud filter expression to query disk selection [OPTIONAL]
     -p    Prefix to be used for naming snapshots.
+          Max character length: 20
           Default if not set: 'gcs' [OPTIONAL]
     -a    Service Account to use. 
           Blank if not set [OPTIONAL]
@@ -130,13 +131,14 @@ By default snapshots are created with a prefix of `gcs`. To give a custom prefix
     Options:
 
        -p  Prefix to be used for naming snapshots.
+           Max character length: 20
            Default if not set: 'gcs' [OPTIONAL]
 
 For example:
 
     ./gcloud-snapshot.sh -p "my-snap"
 
-    (Note: Snapshot names are limited to 62 characters)
+    (Note: Snapshot prefixes are limited to 20 characters)
 
 ### Service Account
 By default snapshots are created with the default gcloud service account. To use a custom service account use the -a flag:

Diff for: gcloud-snapshot.sh

@@ -28,6 +28,7 @@ usage() {
     echo -e "          access to [OPTIONAL]."
     echo -e "    -f    gcloud filter expression to query disk selection [OPTIONAL]"
     echo -e "    -p    Prefix to be used for naming snapshots."
+    echo -e "          Max character length: 20"
     echo -e "          Default if not set: 'gcs' [OPTIONAL]"
     echo -e "    -a    Service Account to use."
     echo -e "          Blank if not set [OPTIONAL]"
@@ -92,7 +93,12 @@ setScriptOptions()
 
     # Snapshot Prefix
     if [[ -n $opt_p ]]; then
-        PREFIX=$opt_p
+        # check if prefix is more than 20 chars
+        if [ ${#opt_p} -ge 20 ]; then
+            PREFIX=${opt_p:0:20}
+        else
+            PREFIX=$opt_p
+        fi
     else
         PREFIX="gcs"
     fi