BASH Programming

How to Use the read Command in Bash

In Bash scripting, the “read” command is used to obtain input from users. Understanding the “read” command is key to making your code more interactive. The “read” command is used to obtain inputted information from the user. This article shows you how to use the “read” command in Bash to interact with users.

First, check out the basic syntax of the “read” command:

read [option] variable

Using the “read” command means that you are interacting with Bash to obtain information from the user. It saves the value in a variable, but with no “$” sign. You will be able to better understand this concept with an example.

Example 1: Using the “read” Command in a Bash Script

To examine the “read” command more in-depth, we will create a simple script that will ask for the user’s name. First, open any text editor; for this tutorial, I am using the Vim text editor due to its many useful features. To install Vim, execute the following command in the terminal:

$sudo apt install vim

Next, type the following in the text file:

#! \bin\bash

echo “Please type your name”

read name

echo “Your name is” $name

Save the file by any name, then press Esc and type “:w readcom.sh.” To run the script, issue the following command:

$ bash readcom.sh

The above script will ask the user to write his/her name. The “read” command will then save the input from the user. The next line will print the name that the user input.

Example 2: Simplifying Code Using the “prompt” Operator

The above example can be simplified further using the “prompt” operator. Let us re-write the above example to comprehend the code:

#! /bin/bash

read –p “Please type your name” name

echo “Your name is” $name

Example 3: Hiding the User Input Using the “secret/silent” Operator

The “-s” flag can be used to hide the input of the user. The following Bash script example shows you how to use the “-s” operator:

#! /bin/bash

read –p “Please type your username” username

read –s –p “Please type your password” $password

Example 4: Limiting the Character Length

The “-n” flag can be used to add a constraint to the number of characters that the user may input.

#!/bin/bash

read –n 8 –p “Please type your username not exceeding 8 characters” username

echo “Your username is” $username

With the “-n” option, the user can still write less than eight characters. To further restrict the input length, the “-N” flag can be used, which limits the user’s response to exactly eight characters.

Example 5: Getting the Input in an Array

The user input can also be taken in an array with the “-a” flag. For instance, to get the user’s name, age, and email address in one go, then we can use an array. Let us look at an example:

#! /bin/bash

echo “Please type your name, age, and email”

read –a array name age email

echo “Your name, age, and email address are: ${array[@]} name age email”

echo “Your name and age are: ${array[@]:0:1} name age”

echo “Your email address is: ${array[2]} email”
  • “${array[@]}” will loop through all variables.
  • To iterate through the indexes 0 to 1, use “${array[@]:0:1}” with the variable names.
  • To obtain the value of a particular variable at a specific index, use “${array[2]}” with the variable name.

Example 6: Adding a Timeout to the “read” Command

As the name of the command indicates, a timeout can be added as a condition of reading the code using the “-t” flag, which makes the user enter information for a specific time. Otherwise, the program will move to the next line of code.

#! \bin\bash

echo “What is the capital of Japan? Answer in 5 seconds”

read –t 5 answer


if [$answer” = “tokyo” ] || [$answer” = “Tokyo” ];

then

echo “Your answer is Correct!

else

echo “Your answer is Wrong!

fi

Conclusion

Getting input from a user input is one of the most important parts of programming, making your programs more interactive. This article showed you how to use the “read” command, one of the key commands in Bash scripting. In this article, you learned about some of the various approaches that you can use with the “read” command, from basic flag operators to advanced operators.

About the author

Sam U

Sam U

I am a professional graphics designer with over 6 years of experience. Currently doing research in virtual reality, augmented reality and mixed reality.
I hardly watch movies but love to read tech related books and articles.