diff --git a/get-installation-access-token.sh b/get-installation-access-token.sh
index b19b7d3..cc922b2 100755
--- a/get-installation-access-token.sh
+++ b/get-installation-access-token.sh
@@ -3,26 +3,26 @@ export PRIVATE_KEY=${1:?Usage: ${0} <private-key> <app-id>}
 export APP_ID=${2:?Usage: ${0} <private-key> <app-id>}
 repo=${GITHUB_REPOSITORY:?Missing required GITHUB_REPOSITORY environment variable}
 
-[[ ! -z "$INPUT_REPO" ]] && repo=$INPUT_REPO
+[ -n "$INPUT_REPO" ] && repo="$INPUT_REPO"
 
-jwt=$(ruby $(dirname $0)/generate_jwt.rb)
-response=$(curl -s -H "Authorization: Bearer ${jwt}" -H "Accept: application/vnd.github.v3+json" https://api.github.com/repos/${repo}/installation)
-installation_id=$(echo $response | jq -r .id)
+jwt=$(ruby "$(dirname "$0")"/generate_jwt.rb)
+response=$(curl -s -H "Authorization: Bearer ${jwt}" -H "Accept: application/vnd.github.v3+json" "https://api.github.com/repos/${repo}/installation")
+installation_id=$(echo "$response" | jq -r .id)
 
 if [ "$installation_id" = "null" ]; then
     echo "Unable to get installation ID. Is the GitHub App installed on ${repo}?"
-    echo $(echo $response | jq -r .message)
+    echo "$response" | jq -r .message
     exit 1
 fi
 
 token=$(curl -s -X POST \
--H "Authorization: Bearer ${jwt}" \
--H "Accept: application/vnd.github.v3+json" \
-https://api.github.com/app/installations/${installation_id}/access_tokens | jq -r .token)
+             -H "Authorization: Bearer ${jwt}" \
+             -H "Accept: application/vnd.github.v3+json" \
+             https://api.github.com/app/installations/"${installation_id}"/access_tokens | jq -r .token)
 
 if [ "$token" = "null" ]; then
-  echo "Unable to generate installation access token"
-  exit 1
+    echo "Unable to generate installation access token"
+    exit 1
 fi
 
-echo ::set-output name=token::${token}
+echo "::set-output name=token::${token}"