后台使用top命令需注意使用-b选项

通过其他程序或脚本在非交互式模式下调用top命令，经常会出现:
   top: failed tty get 错误

解决办法：加个-b 选项皆可

-b : Batch mode operation
   Starts top in <A1><AF>Batch mode<A1><AF>, which could be useful for sending output from top to other programs or to a file. In this mode, top will not accept input and runs until the iterations limit you<A1><AF>ve set with the <A1><AF>-n<A1><AF> command-line option or until killed.

例如执行：
top -bn 1

监控某个进程的状态：
top -bn 1 -p 14370 | grep cmdname>>stats.log