循環變量不會傳遞給 Jenkins 中的 shell 腳本

我正在嘗試將循環變量傳遞給 shell 腳本，但我的 shell 腳本獲取了一個空變量值

pipeline {
 agent any     
  stages {     
   stage('Test') {     
    steps {                 
     script {
      elements = ['1', '2', '3', '4']
      for (String val in elements){
       echo val
       check = sh (script: """bash ./check_access/check.sh ${val}""", returnStdout: true).trim()                            
       echo "check: ${check}"                          
      }
     }
    }
   }
  }
}

./check_access/check.sh

#!/bin/sh
echo "val: $val"

我得到的結果

18:13:30  1
18:13:31  + bash ./check_access/check.sh 1
18:13:31  check: val:
.
.
.
18:13:31  4
18:13:32  + bash ./check_access/check.sh 4
18:13:32  check: val:

想要的結果

bash ./check_access/check.sh 1
check: val: 1
.
.
.
bash ./check_access/check.sh 4
check: val: 4

能否請你幫忙