python 执行shell命令并将结果保存的实例

def run_cmd(cmd):
 result_str=''
 process = subprocess.Popen(cmd, shell=True,
    stdout=subprocess.PIPE, stderr=subprocess.PIPE)
 result_f = process.stdout
 error_f = process.stderr
 errors = error_f.read()
 if errors: pass
 result_str = result_f.read().strip()
 if result_f:
  result_f.close()
 if error_f:
  error_f.close()
 return result_str

def run_cmd2file(cmd):
 fdout = open("file_out.log",'a')
 fderr = open("file_err.log",'a')
 p = subprocess.Popen(cmd, stdout=fdout, stderr=fderr, shell=True)
 if p.poll():
  return
 p.wait()
 return