1. [root@www ~]# echo `expr ${RANDOM} % 14 + 1 `
10
[root@www ~]#
2. [root@www ~]# echo $(( ${RANDOM} % 14 + 1 ))
4
[root@www ~]#
3. [root@www ~]# echo $[ ${RANDOM} % 14 + 1 ]
13
[root@www ~]#
4. [root@www ~]# let m=${RANDOM}%14+1 ;echo $m
8
[root@www ~]#
虽然Bash shell 有四种算术运算方法，但并不是每一种都是跨平台的，建议使用expr。
另外，我们在 script 中经常有加1操作，以下四法皆可：
m=$[ m + 1]
m=`expr $m + 1`
m=$(($m + 1))
let m=m+1
用mysql函数实现：
mysql> select rand();
+--------------------+
| rand() |
+--------------------+
| 0.9146193386191682 |
+--------------------+
1 row in set (0.00 sec)
mysql> select ceil(100*rand()),ceil(100*rand());
+------------------+------------------+
| ceil(100*rand()) | ceil(100*rand()) |
+------------------+------------------+
| 31 | 78 |
+------------------+------------------+
1 row in set (0.00 sec)
mysql> select floor(100*rand()),floor(100*rand());
+-------------------+-------------------+
| floor(100*rand()) | floor(100*rand()) |
+-------------------+-------------------+
| 95 | 45 |
+-------------------+-------------------+
1 row in set (0.00 sec)
mysql> select mod(floor(100*rand()),15),floor(100*rand());
+---------------------------+-------------------+
| mod(floor(100*rand()),15) | floor(100*rand()) |
+---------------------------+-------------------+
| 11 | 69 |
+---------------------------+-------------------+
1 row in set (0.00 sec)
mysql> select mod(floor(100*rand()),15),floor(100*rand()) % 15;
+---------------------------+------------------------+
| mod(floor(100*rand()),15) | floor(100*rand()) % 15 |
+---------------------------+------------------------+
| 9 | 11 |
+---------------------------+------------------------+
1 row in set (0.00 sec)
mysql>
[root@192 ~]# /usr/bin/mysql -p3306 --socket=/data/3306/mysql.sock -e "select mod(ceil(100000*rand()),14) + 1 ;" | awk 'NR==2{print $0}'
6
[root@192 ~]# /usr/bin/mysql -p3306 --socket=/data/3306/mysql.sock -e "select mod(ceil(100000*rand()),14) + 1 ;" | awk 'NR==2{print $0}'
14
[root@192 ~]# /usr/bin/mysql -p3306 --socket=/data/3306/mysql.sock -e "select mod(ceil(100000*rand()),14) + 1 ;" | awk 'NR==2{print $0}'
3
[root@192 ~]# /usr/bin/mysql -p3306 --socket=/data/3306/mysql.sock -e "select mod(ceil(100000*rand()),14) + 1 ;" | awk 'NR==2{print $0}'
8
[root@192 ~]# /usr/bin/mysql -p3306 --socket=/data/3306/mysql.sock -e "select mod(ceil(100000*rand()),14) + 1 ;" | awk 'NR==2{print $0}'
7
[root@192 ~]#
完美，练习mysql的函数。
