Store the output of date and watch command to a file

I am a newbie to linux and I am trying to watch a command and try to log it into a file. I tried watch -t -n 10 "(date '+TIME:%H:%M:%S' ; ps aux | grep "pattern" | wc -l)" >> logfile and am expecting a result like TIME: 10:32:30 12 TIME: 10:32:40 18 TIME: 10:32:50 2 to be stored in logfile. However, when the logfile has unprintable characters in in. How do I get this kind of output from the comman

[mumumu-tan]

tee コマンドを使う解が秀逸。これは、 tee コマンドを含めてクォートし、 watch コマンドへの引数にしているのがミソ。そうしないと watch の出力そのものがパイプされてしまう。

[tvsk]

watchコマンドによる目検とロギングの実践例。

[tuki0918]

“watch -t -n 10 "(date '+TIME:%H:%M:%S' ; ps aux | grep "pattern" | wc -l) | tee -a logfile"”