shell编程实例五判断用户是否在线

#!/bin/sh

check_user()
{
 user=`who | cut -f1 -d ' '`
 for name in $user
 do
  if [ $name = $1 ]
  then
   return 1
  else
   return 0
  fi
 done
}

while true
do
 echo "input user name:\c"
 read name
 check_user $name
 if [ $? -eq 1 ]
 then
  echo "user name is online"
 else
  echo "user name is offline"
 fi
done