for, while, until loop, and break out and continue to terminate the loop

for loop

format

for 变量名 in 取值列表
do
　 命令序列
done

Three different formats of variable i

for i in { } 用法

for i in $(seq 1 10)

Supplement: $(seq 1 2 10)

for ((i=1;i<=10;i++))

Instance

Check the host status according to the IP address. The
IP address is stored in the ipadds.txt file, one per line.
Use the ping command to check the connectivity of each host

while statement

format

while 条件测试操作
do
    命令序列
done

Format example

Instance

Guess the commodity price game
Obtain a random number through the variable RANDOM.
Prompt the user to guess and record the number of times. After the guess is successful , exit the loop

until statement

format

until 条件测试操作
do
    命令序列
done

Test a certain condition repeatedly, and execute it repeatedly as long as the condition is not established

Double loop

break out of the loop

break out of the two-layer loop

continue to abort a command in a loop, but not completely abort the entire command

IFS field separator

Contains spaces, tabs, and newlines by default

Instance