import json

SN_JSON_PATH = '/opt/tsg/etc/tsg_sn.json'

def tsg_get_sn():
    try:
        with open(SN_JSON_PATH) as json_fp:
            json_dict = json.load(json_fp)
            return json_dict['sn']
    except IOError:
        return ""
        
def main():
    sn = tsg_get_sn()
    if len(sn) > 0:
        print("%s" %(sn))
    else:
        print("can't get sn")
        
if __name__ == '__main__':
    main()