Bash Script to Remove Spaces from String

Use echo "$string" | tr -d ' ' in Bash to remove all spaces from a string.

Examples

Inputhello world

Outputhelloworld

Input spaced out string

Outputspacedoutstring

Inputnospace

Outputnospace

How to Think About It

To remove spaces from a string in Bash, think of filtering out the space characters. You can do this by passing the string through a command that deletes spaces, like tr -d ' ', which removes all spaces from the input.

Algorithm

1

Get the input string.

2

Use a command to delete all space characters from the string.

3

Output the resulting string without spaces.

Code

bash

#!/bin/bash

string="hello world from bash"
result=$(echo "$string" | tr -d ' ')
echo "$result"

Output

helloworldfrombash

Dry Run

Let's trace the string 'hello world from bash' through the code

1

Input string

string = 'hello world from bash'

2

Remove spaces

echo "$string" | tr -d ' ' => 'helloworldfrombash'

3

Output result

result = 'helloworldfrombash' printed

Step	String Value
Initial	hello world from bash
After tr -d ' '	helloworldfrombash

Why This Works

Step 1: Echo the string

The echo command outputs the string so it can be processed.

Step 2: Delete spaces

The tr -d ' ' command deletes all space characters from the input.

Step 3: Store and print

The result is stored in a variable and printed without spaces.

Alternative Approaches

Using parameter expansion

bash

#!/bin/bash
string="hello world from bash"
result="${string// /}"
echo "$result"

This method uses Bash's built-in string replacement and is faster since it avoids external commands.

Using sed

bash

#!/bin/bash
string="hello world from bash"
result=$(echo "$string" | sed 's/ //g')
echo "$result"

This uses <code>sed</code> to globally remove spaces but is slower than parameter expansion.

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

Time Complexity

The operation scans each character once to remove spaces, so it runs in linear time relative to string length.

Space Complexity

A new string without spaces is created, so space used is proportional to the input string size.

Which Approach is Fastest?

Parameter expansion is fastest as it avoids spawning external processes, while tr and sed are slower due to command execution overhead.

Approach	Time	Space	Best For
Parameter Expansion	O(n)	O(n)	Fastest, pure Bash
tr -d ' '	O(n)	O(n)	Simple and readable
sed substitution	O(n)	O(n)	Flexible pattern removal