How to Bash Concatenate Strings: Joining Variables in Linux


The majority of programming languages can connect two or more strings. One programming language that makes it effortless to concatenate variables is bash.

What makes bash special is that string variables can be connected without the use of dedicated commands or functions. In other words, to combine string data, users can use simple variable manipulation or apply the same logic with the addition assignment operator (+=).

In this tutorial, we will explain bash scripting, go over what bash concatenate strings are, and provide a variety of ways to concatenate strings.

Download Complete Linux Commands Cheat Sheet

What Is Bash Scripting?

Bash shell scripting allows users to execute hundreds of Linux commands with a single script instead of writing them all down one by one. It is extra helpful for users looking to automate their physical or virtual private servers (VPS) and increase productivity.

For example, any command a user can run natively on a terminal can be put into a bash script. This also applies to functions, so instead of writing them down every time, users only need to write a function once and reuse it in any bash scripts.

Any script starts with a .sh file and contains a similar structure:

#!/bin/bash
# Creates a new variable "Hello, World"
mybashvariable="Hello, World"
echo $mybashvariable

The first line tells the terminal to run the script using bash exclusively, and all the following lines are the actual script itself.

In this particular example, the script created a new variable named mybashvariable and gave it a “Hello, World” value, and the script will print the value out.

Concatenation operation in bash is the process of attaching a string to the end of another string. Bash allows its users to concatenate strings by writing strings one after the other or joining them using the += operator.

String Concatenation – Adding One String Variable After the Other

The simplest string concatenation method is adding one string variable after the other. The following sections will show three different ways to do just that.

String Concatenation Using Literal Strings

Literal strings are printed literally, and there are two ways to print out a string literal – using singular quotes or a backlash symbol with regular double quotes. For example, we will create a new literal string variable without quotes and echo it:

#!/bin/bash
variablename=\usr\bin\env
echo "$variablename"

In this case, the result would be:

# Result
usrbinenv

Now, when we add singular or double quotes to the string variable name, the echo command will print the value literally:

#!/bin/bash
variablename="\usr\bin\env"
echo "$variablename"

Here’s the result:

# Result
\usr\bin\env

Next, we will apply this logic to concatenate two strings:

#!/bin/bash
variablename="\usr\bin\env"
echo "$variablename Bash_Is_Awesome"

We can also cover the last line’s variable using rounded brackets in order to guard it. Curly brackets are helpful if you got a variety of variables:

echo "${variablename} Bash_Is_Awesome"

In both cases, the result will be shown as:

\usr\bin\env Bash_Is_Awesome

String Concatenation of Multiple Variables

Multiple string variables can be easily joined together with clear-cut variable manipulation.

For example, in the following bash script, we will use three different variables to create combined values. The echo command will subsequently print out the string data:

#!/bin/bash
variablename="\usr\bin\env "
myvariable="_Awesome"
anothervariable="$variablename"Bash_Is"$myvariable"
echo "$anothervariable"

Here’s what the result will look like:

\usr\bin\env Bash_Is_Awesome

String Concatenation of Numbers and Strings

Bash allows its users to concatenate one or more variables that are not string-type. For this reason, it is possible to concatenate multiple variables, which can be strings or numbers:

#!/bin/bash
firstvariable=" Hello, World "
secondvariable="Hello, Hostinger "
thirdvariable=" I now know how to concatenate strings in bash."
fourthvariable="$secondvariable"and"$firstvariable"means"$thirdvariable"
echo $fourthvariable
Bash string concatenation of numbers and strings

String Concatenation Using the += Operator

Another way to join two or more strings to make a concatenated string is to use the addition assignment operator (+=). This operator makes it possible to connect strings using one or more variables.

For example, the following script can be used to join two strings with the use of a single variable:

#!/bin/bash
mystring="I would like to generate a meaningful output, please. "
mystring+="Not a chance, friend!"
echo "$mystring"
Connecting both strings without any built-in function or command in bash. Combined values are achieved using the append += operator

A similar result can be achieved using two variables:

#!/bin/bash
firststring="This is a single string. "
secondstring="Which makes this a resulting string."
# Curly brackets between $secondvariable are called variable interpolation.
firststring+="${secondstring}"
echo $firststring
Bash append string operator use-case example. Two strings are taken and concatenated string is made with the help of the append operator

Concatenating Numeric Strings

The append operator method can also be used exclusively to append numeric string variables.

#!/bin/bash
numeric_string=2050
numeric_string+=0502
echo $numeric_string
Bash script to join numeric string variables. Plus and equal sign correspond to append operator

However, if you would like to add the numbers together, this logic needs to be used:

#!/bin/bash
x=3
y=5
z=6
((x+=y+=z))
echo $x
Bash script to add three numbers together

Concatenating Strings Using Bash for Loop

A more advanced way of using the bash concatenate functionality is implementing it into the bash for loop.

In the following example, we got a myvariable with three strings and a variable named results with an empty string. With the help of the bash for loop, we will be able to combine strings from myvariable with our string:

#!/bin/bash
myvariable="bash concatenation Hostinger"
results=""
for i in $myvariable
do
results+="The answer is $i... "
done
echo $results
Bash for loop example in a bash script. It is used to join three strings with the preferred string. Echo command prints out the combined result

Conclusion

The bash programming language is a convenient and efficient tool for various variable manipulation actions. One of the most important examples is the ability to join different string variables into one.

In this tutorial, we’ve gone through the definition of bash scripting and concatenation. We also learned how to join string variables with two different methods.

We hope you found this tutorial useful. If you have any further questions, feel free to leave them in the comments section below.

Author

Ignas is a Technical Content Writer at Hostinger. After helping people tackle even the most complex technical issues as a Customer Success Specialist, his current goal is to write easy-to-follow articles so that these issues will not happen at all. During his free time, Ignas likes to play video games and fix up things around his house.



Source link

Leave a Comment

Pin It on Pinterest