How to Return String From Bash Function [4 Methods]

To return a string from the function in Bash, use the following methods:

1. Using “echo” Command: my_function() { echo "my string";}
2. Using “printf” Command: my_function() { printf "my string\n";}
3. Using Global Variable: my_function() { global_var="my string";}
4. Using Here-document: my_function() { cat << EOF multiline string EOF;}

In bash, functions do not return strings directly, the echo command or printf command can be employed to return the string from the function in Bash. Moreover, you can declare a global variable for returning the string from the Bash function. To get the multiline string from the function in Bash, you need to include the here-document inside the function. In this article, I am going to show you 4 methods to return a string from the bash function. Read on.

1. Using “echo” Command

Leveraging the echo command provides different ways to capture the string output of the function in Bash. The command substitution method or process substitution method can be incorporated with this command to return a string from the bash function. Here are 3 cases of it:

1.1 Using “echo” Command Alone

The easiest way to get a string from a bash function is to use only the echo command within the function. The echo command will print the output when the function is called. Here’s how:

#!/bin/bash

# Define a function named get_string
function get_string() {
  echo "Hello, World!"
}

# Call the get_string function
get_string

The script returns the string “Hello, World!” using the “echo” command.

1.2 Using “echo” Command With Command Substitution

To return a string from the bash function, use the command substitution method with the echo command. The command substitution takes the function output echoing by the “echo” command and assigns it directly to a variable using the $(...) syntax. Here is the full bash script to do this:

#!/bin/bash

# Define a function named get_user
function get_user {
  echo $USER
}

# Call the get_user function and capture the result in the variable "username"
username=$(get_user)

# Print a message using the value stored in the "username" variable
echo "Hello, $username!"

As you can see, the script returns a string containing the current user’s username.

1.3 Using “echo” Command With Process Substitution

The process substitution method encapsulates the function’s output (string of the echo command) using $(< <(...)) syntax. It allows to use the the output of the function as a file or input stream. This method is advantageous for advanced string manipulation. Now, copy the script to return a string from the function using process substitution:

#!/bin/bash

function get_result() {
  local string="Hello, I am using Ubuntu."
  echo "$string"
}

result=$(< <(get_result))
echo "$result"

You can notice that the function returns the string “Hello, I am using Ubuntu.”.

2. Using “printf” Command

The printf command provides precise control over the output of the function. To return intricate and dynamic strings from a Bash function, using this method is a great idea. Now, check the bash script to see how the function returns a string with the printf command:

#!/bin/bash

function return_string {
  printf "Hello, I am using Linux\n"
}

# Call the return_string function
return_string

You can see that the function returns the string “Hello, I am using Linux”.

3. Using Global Variable

A global variable is accessible from inside or outside of a function. Use such a variable within a function to return any string from the function. Here’s the entire bash script to get a clear insight:

#!/bin/bash

# Define a global variable
string_global() {
  string="Hello, I am using Ubuntu."
}

string_global
echo $string

The function returns a string “Hello, I am using Ubuntu.” using a global variable.

4. Using Here-document

To return multiline strings from a function, one of the convenient ways is to use the cat command with a here document. The here document can craft a string block without manually escaping special characters. Here is how to return a multiline string from a function:

#!/bin/bash

function get_message {
  cat <<EOF
Hello, welcome to Linuxsimply.

I am using Ubuntu.
EOF
}

get_message

This script returns the multiline string from the function using here document.

Practice Tasks on Returning String From Bash Function

Elevate your Bash scripting abilities by practicing the following tasks:

1. Define a function that uses a global variable to return “hello Linux” from the bash function.
2. Develop a function that checks if a string is empty and returns an appropriate message.
3. Write a Bash script that defines a function string_length that takes a string as a parameter and returns its length.
4. Generate a function that takes a string as a parameter and returns its uppercase version in the output.
5. Develop a function that takes a string and returns its reversed form in the output.

Conclusion

I hope that this article has helped you understand the ways to get a string from a function in bash. In this article, I have shown 4 detailed methods to get a string from a function. You can choose the method of your choice. Happy scripting!

People Also Ask

How can I return string from a function in Bash?

To return a string from a function in Bash, you can apply the echo command within the function alone or with the command substitution method or process substitution method. Also, you can define a global variable or here-document in the function to accomplish this task.

How do you return an empty string in Bash?

In Bash, you can return an empty string from a function by simply not echoing any content within the function. Here’s an example bash script:

#!/bin/bash

get_empty_string() {
# This function returns an empty string
}

result=$(get_empty_string)
echo "Result: '$result'"

Can a string have numbers?

Yes, a string can have numbers. In the programming language, a string is usually a collection of characters. These characters can be letters, numbers, symbols, or a combination of them.

How do I extract a string from a line in Bash?

To extract a string from a line in Bash, you can use the awk command. Suppose, you want to extract the “Linux” word from a line “Hello Linux Users.”. To do so, apply word=$(echo "$line" | awk '{print $2}') in the Bash script. Here, the awk command uses the $2 parameter to extract the 2nd word from the line.

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