流程控制语句(2)
时间：2005-12-12 来源：txkss
流程结构
echo "$user is logged"
else
echo "$user is not logged"
格式:
if command-1
then
command-2
command-3
fi
if command-1
then
command-2
command-3
fi
If就是判断表达式是否为真,如为真就执行then与fi之间的动作,否则跳过
else结构
格式:
if command-1
then
command-2
command-3
else
command
command
fi
if command-1
then
command-2
command-3
else
command
command
fi
先执行com1然后检测退出状态,如果为真就执行后面then和else之间的命令,跳过else和fi之间的命令
如果退出状态为假,则跳过then和else之间的命令执行else与fi之间的命令
任何情况下只执行一组命令
user="$1"
if who|grep "^$user " >/dev/null
then
echo "$user is logged"
else
echo "$user is not logged"
fi
if who|grep "^$user " >/dev/null
then
echo "$user is logged"
else
echo "$user is not logged"
fi
执行过程：
#chmod 744 login.txt
#./login.txt root
root is logged
#chmod 744 login.txt
#./login.txt root
root is logged
相关阅读 更多 +
