WC
-c, --bytes print the byte counts
-m, --chars print the character counts
-l, --lines print the newline counts
--files0-from=F read input from the files specified by
NUL-terminated names in file F;
If F is - then read names from standard input
-L, --max-line-length print the length of the longest line
-w, --words print the word counts
--help display this help and exit
--version output version information and exit
who | wc -l
#超级管理员
$普通管理员
原文：http://www.cnblogs.com/baxk/p/5085861.html