String length (${#var}) in Bash Scripting - Step-by-Step Execution

Concept Flow - String length (${#var})

Start with variable

↓

Apply ${#var}

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Calculate length

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Return length as number

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Use or display length

This flow shows how bash calculates the length of a string stored in a variable using ${#var}.

Execution Sample

Bash Scripting

name="hello"
length=${#name}
echo $length

This script stores 'hello' in name, calculates its length, and prints it.

Execution Table

Step	Variable	Action	Value	Output
1	name	Assign 'hello'	hello
2	length	Calculate ${#name}	5
3	echo $length	Print length	5	5

💡 Script ends after printing the length 5.

Variable Tracker

Variable	Start	After 1	After 2	Final
name		hello	hello	hello
length			5	5

Key Moments - 2 Insights

Why does ${#name} give 5 instead of the string itself?

Because ${#name} returns the number of characters in the string stored in name, not the string content itself. See execution_table step 2.

What happens if the variable is empty or unset?

If the variable is empty or unset, ${#var} returns 0, meaning the string length is zero. This is shown by the initial empty state in variable_tracker.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of 'length' after step 2?

A 5

B hello

C 0

D ${#name}

💡 Hint

Check the 'Value' column in row for step 2 in execution_table.

At which step is the string length printed to the screen?

A Step 1

B Step 2

C Step 3

D No step prints output

💡 Hint

Look for the 'Output' column showing printed value in execution_table.

If name was empty, what would ${#name} return?

A An error

B 0

C Empty string

D 1

💡 Hint

Refer to key_moments about empty or unset variable behavior.

Concept Snapshot

Use ${#var} to get the length of the string in var.
It returns the number of characters as a number.
If var is empty or unset, length is 0.
Example: name="hi"; echo ${#name} outputs 2.

Full Transcript

This lesson shows how to find the length of a string in bash using ${#var}. First, assign a string to a variable. Then use ${#var} to get its length as a number. Finally, print or use that number. If the variable is empty, the length is zero. The example uses name="hello" and prints 5 because hello has 5 letters.