Bash Script to Find Length of String

In Bash, you can find the length of a string using ${#string}, for example: length=${#mystring} stores the length of mystring in length.

Examples

Inputhello

Output5

InputBash scripting

Output14

Input

Output0

How to Think About It

To find the length of a string in Bash, think of the string as a sequence of characters. You want to count how many characters it has. Bash provides a simple way to get this count using the ${#string} syntax, which directly returns the number of characters in the string variable.

Algorithm

1

Get the string input or define a string variable.

2

Use the syntax ${#string} to get the length of the string.

3

Store or print the length as needed.

Code

bash

#!/bin/bash
mystring="Hello, world!"
length=${#mystring}
echo "Length of string: $length"

Output

Length of string: 13

Dry Run

Let's trace the string "Hello, world!" through the code

1

Define string

mystring="Hello, world!"

2

Calculate length

length=${#mystring} = 13

3

Print length

Output: Length of string: 13

Variable	Value
mystring	Hello, world!
length	13

Why This Works

Step 1: Use of ${#string}

The ${#string} syntax in Bash returns the number of characters in the variable string.

Step 2: Assign length to variable

We assign this length to a variable like length to use or print it later.

Step 3: Print the result

Using echo, we display the length to the user.

Alternative Approaches

Using expr command

bash

mystring="Hello"
length=$(expr length "$mystring")
echo "$length"

This uses an external command and is less efficient than built-in syntax.

Using wc command

bash

mystring="Hello"
length=$(echo -n "$mystring" | wc -c)
echo "$length"

This counts bytes via wc, useful if you want to handle input from echo, but slower than built-in.

Complexity: O(1) time, O(1) space

Time Complexity

Getting the length with ${#string} is a constant time operation because Bash stores string length metadata.

Space Complexity

No extra memory is needed beyond the input string and a variable to store the length.

Which Approach is Fastest?

Using ${#string} is fastest as it is built-in; external commands like expr or wc add overhead.

Approach	Time	Space	Best For
${#string}	O(1)	O(1)	Simple and fast length retrieval
expr length	O(n)	O(1)	Legacy scripts or compatibility
echo + wc -c	O(n)	O(1)	Counting bytes from output streams