第一种写法
macname@MacdeMBP ~ % who > users macname@MacdeMBP ~ % wc -l users 4 users macname@MacdeMBP ~ %
第二种写法
macname@MacdeMBP ~ % who | wc -l 4 macname@MacdeMBP ~ %
macname@MacdeMBP ~ % who > users macname@MacdeMBP ~ % wc -l users 4 users macname@MacdeMBP ~ %
macname@MacdeMBP ~ % who | wc -l 4 macname@MacdeMBP ~ %