Core grammar:
-I declare it as an integer.
-The declaration is not an array.
-f statement doesn't work.
-r statement is not read-only.
The above are commonly used, of course, others can be obtained through man declaration.
By default, if we want to get a variable of numeric integer type for the declaration string of an object, we need to declare it this time.
Let's look at a situation:
Price = 10
num=3
Echo $ price * quantity
-
10*3
If the declaration is declare, then it is as follows.
inter 12 @ inter 12:/tmp $ declare-I price = 10；
inter 12 @ inter 12:/tmp $ declare-I num = 3；
inter 12 @ inter 12:/tmp $ declare-I total = $ price * $ num
inter 12 @ inter 12:/tmp $ echo $ total
30
In fact, there is another way to deal with declare, just look at the code.
1 #! /bin/bash
2 # test statement and $ (())
three
four
5 user statement () {
six
7 statement-i num =1;
8 statement -i price = 5;
9 declaration-my total =$num*$price
10 echo' declares that the style is and the result is' $ total'
1 1 }
12
13
14 userDouble(){
15
16 number d= 1
17 price_d=5
18 total_d=$ ((quantity _d * price _ d))
19 echo "double price for users is" $total_d "
20 }
2 1
22
23 user statement
24 user double
-
inter 12 @ inter 12:~/my shell/shell/declare $。 /test
The declaration style is that the result is 5.
The double price for users is 5.
$((num_d*price_d)): means to perform the calculation and return the result. If it is ((num_d*price_d)), the calculation will not return the result. Please pay attention here!
Interactive command reading
This is also a very common command, according to the different input of end users, execute different script commands!
1 #! /bin/bash
2
3 echo'-This is the first line-'
4 echo' 1. When you select 1, echo heihei
5 Echo' 2. Echo haha when you choose 2'
6 echo -n' Select Yes'
7 reading choice
eight
9 if[$ selection = " 1 "]； then
10 echo' hehe'
1 1 elif[$ selection = " 2 "]； then
12 echo' haha'
13 others
14 echoes "Invalid option"
15 fi