One command lets you understand the common parameters of the read command in the shell

We know that there are two ways to receive incoming parameters in Shell. One is to pass parameters through the script, and the other is to receive the incoming parameters through read. A simple example of passing parameters through a script is as follows:

# Pass through the script, where $0 refers to the script name, $1 is the first parameter, and $2 is the second parameter [root@host ~]# ./script.sh 1 2
Total = 3
[root@host ~]# vim script.sh
#!/bin/bash
function add() {
  total=$(expr $1 + $2)
  echo -e "Total = $total"
}
add $1 $2

Let's look at receiving the incoming parameters through read. First, look at the basic format of read:

read [-rs] [-a ARRAY] [-d delim] [-n nchars] [-N nchars] [-p prompt] [-t timeout] [var1 var2 var3......]

[root@host ~]# ./script.sh 
Enter Password:
The password your input is: Test@1234\
[root@host ~]# vim script.sh
#!/bin/bash
read -n10 -t30 -r -s -d $ -p "Enter Password:" password
echo -e "\nThe password your input is:$password"

• -p prompt statement, followed by input prompt information, here is 'Enter Password: '
• -n parameter number, sometimes you need to limit the password length, or other input length restrictions, such as [Y/N], only enter one input, -n1
• -s Shield echo, the input content is not displayed on the screen, generally used for password input
• -t Waiting time, here set to 30 seconds, if no input is made within 30 seconds or the input is incomplete, the system will terminate.
• -d Input limit, here is $, input to $, natural termination of input
• -r blocks the translation function of special characters \, and treats them as ordinary characters after adding them

From the above example, most of the common functions above are basically covered, especially the -p, -n, -t, -s and other parameters, which can be used to learn the read command well.

Summarize

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