比较两个数大小的语法： [root@dbserver ~]# cat if_01_01 read -p "please input two number:" a b if [ $a -gt $b ] then echo "yes,$a > $b" elif [ $a -eq $b ] then echo "yes,$a = $b" else echo "yes,$a < $b" fi 执行结果： [root@dbserver ~]# sh if_01_01 please input two number:4 5 yes,4 < 5 [root@dbserver ~]# sh if_01_01 please input two number:4 4 yes,4 = 4 [root@dbserver ~]# sh if_01_01 please input two number:5 4 yes,5 > 4
传参程序，目的在于判断输入值的合法性，首先是参数的个数是否满足两个. [root@dbserver ~]# vi if_01_01.sh #!/bin/bash a=$1 b=$2 if [ $# -ne 2 ] ----说明：$# 获取当前shell命令行中参数的总个数
then echo "Usage:sh $0 num1 num2" exit fi if [ $a -gt $b ] then echo "yes,$a > $b" elif [ $a -lt $b ] then echo "yes,$a < $b" else echo "yes,$a = $b" 执行结果： [root@dbserver ~]# sh if_01_01.sh 2 3 4 Usage:sh if_01_01.sh num1 num2
现在同时判断输入参数是否为两个以及参数的正确性.
[root@dbserver ~]# cat if_01_01.sh
#!/bin/bash
a=$1
b=$2
if [ $# -ne 2 ]
then
echo "Usage:sh $0 num1 num2"
exit
fi
[ -n "echo $1|sed 's/[0-9]//g'" ] && echo "the first data must be number" && exit 1 -----说明：sed s/要替换的字符串/新的字符串/g
[ -n "echo $2|sed 's/[0-9]//g'" ] && echo "the second data must be number" && exit 1
if
[ $a -gt $b ]
then
echo "yes,$a > $b"
elif
[ $a -eq $b ]
then
echo "yes,$a = $b"
else
echo "yes,$a < $b"
fi
执行结果：
[root@dbserver ~]# sh if_01_01.sh 2 3k
the second data must be number
[root@dbserver ~]# sh if_01_01.sh 2k 3
the first data must be number
[root@dbserver ~]# sh if_01_01.sh 2k 3k
the first data must be number
[root@dbserver ~]# sh if_01_01.sh 2 36
yes,2 < 36
