How to Concatenate Strings in Bash

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How to Concatenate Strings in Bash

Author：JIYIK Last Updated：2025/04/05 Views：

String concatenation is one of the most widely used operations in programming. It refers to connecting two or more strings by putting one string at the end of another string. To concatenate strings in Bash, we can write string variables one after another or use +=the operator to concatenate.

Bash string concatenation puts one string variable at the end of another string variable

We can concatenate strings by placing the string variables consecutively one after another.

STR1="Delft"
STR2="Stack"

STR3="$STR1$STR2"

echo "$STR3"

Output:

DelftStack

In the above example, we concatenate STR1and STR3and assign the concatenated string to STR3. Double quotes (" ")are used to prevent splitting or globbing issues.

We use echothe command to print the output.

Concatenate one or more variables with a string

STR1="Delft"

STR3="${STR1}-Stack"

echo "$STR3"

Output:

Delft-Stack

Here, {}it is used to separate string variables and string literals.

It concatenates a string variable STR1with a string literal .-Stack

Concatenate two or more strings together

We can place string variables and characters consecutively and concatenate two or more string variables together.

STR1="Delft"
STR2="-Stack"
STR3="Check them out!!"

STR4="${STR1}${STR2} has great programming articles.${STR3}"

echo "$STR4"

Output:

Delft-Stack has great programming articles.Check them out!!

Concatenate numbers and string characters

Bash does not distinguish between variable types when concatenating variables. They are interpreted as integers or strings, depending on the context.

STR1="FIVE-"
STR2=5

STR4="$STR1$STR2"

echo "$STR4"

Output:

FIVE-5

It concatenates the string variables FIVE-and .5

`+=`String concatenation using the operator

BashIt also allows +=string concatenation using the operator. Simple a+=bcan be understood as a=a+b.

STR1="Delft"
STR2="-Stack"

STR1+=$STR2

echo "$STR1"

Output:

Delft-Stack

Here, STR2is appended STR1to the end of and the result is stored in STR1the variable.

To append multiple values, we can use a simple forloop.

NUMS=""
for NUM in 'One' 'Two' 'Three' 'Four'; do
  NUMS+="${NUM} "
done

echo "$NUMS"

Output:

One Two Three Four

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