Shell循环语句：if

[root@master1-192-168-117-18 ~]# vim mkcdrom.sh

#!/bin/bash
DIR="/media/cdrom"
if [ ! -e $DIR ]
then
mkdir -p $DIR
fi

[root@master1-192-168-117-18 ~]# vim chkhost.sh
#!/bin/bash

ping -c 3 -i 0.2 -W 3 $1 &> /dev/null
if [ $? -eq 0 ]
then
echo "Host $1 is on-line"
else
echo "Host $1 is off-line"
fi

[root@master1-192-168-117-18 ~]# bash chkhost.sh 192.168.1.11
Host 192.168.1.11 is on-line

注释：-c参数来规定尝试的次数，并使用-i参数定义每个数据包的发送间隔，以及使用-W参数定义等待超时时间

[root@master1-192-168-117-18 ~]# vim chkscore.sh
#!/bin/bash
read -p "Enter your score (0-100) :" GRADE
if [ $GRADE -gt 100 ];
then
echo "$GRADE is Error"
elif [ $GRADE -ge 85 ] && [ $GRADE -le 100 ];
then
echo "$GRADE is Excellent"
elif [ $GRADE -ge 70 ] && [ $GRADE -le 84 ];
then
echo "$GRADE is Pass"
else
echo "$GRADE is Fail"
fi
[root@master1-192-168-117-18 ~]# bash chkscore.sh
Enter your score (0-100) :200
200 is Error
[root@master1-192-168-117-18 ~]# bash chkscore.sh
Enter your score (0-100) :93
93 is Excellent
[root@master1-192-168-117-18 ~]# bash chkscore.sh
Enter your score (0-100) :80
80 is Pass
[root@master1-192-168-117-18 ~]# bash chkscore.sh
Enter your score (0-100) :23
23 is Fail