String variables in Bash Scripting

Introduction

String variables let you store words or sentences to use later in your script.

To save a user's name and greet them.

To hold a file path for easy reuse.

To keep a message that you want to print multiple times.

To store command output for processing.

To build a sentence from smaller parts.

Syntax

Bash Scripting

variable_name="your text here"

Use double quotes to keep spaces and special characters intact.

No spaces around the equal sign (=) when assigning.

Examples

Stores the word Alice in the variable named 'name'.

Bash Scripting

name="Alice"

Stores a full sentence with punctuation.

Bash Scripting

greeting="Hello, world!"

Stores a file path as a string.

Bash Scripting

path="/home/user/docs"

Sample Program

This script stores a name and then creates a greeting using that name. It prints the greeting.

Bash Scripting

#!/bin/bash

name="Bob"
greeting="Hello, $name!"
echo "$greeting"

Important Notes

To use the value of a string variable, prefix it with a dollar sign ($).

Always quote variables when using them to avoid word splitting or globbing.

Variable names should only contain letters, numbers, and underscores, and cannot start with a number.

Summary

String variables store text for reuse in scripts.

Assign strings with no spaces around = and use quotes.

Use $variable_name to access the stored text.

Practice

1. What is the correct way to assign the string Hello to a variable named greeting in bash?

easy

A. greeting="Hello"

B. greeting = "Hello"

C. greeting: "Hello"

D. greeting <- "Hello"

Solution

1. Step 1: Understand bash variable assignment syntax

   In bash, variable assignment must have no spaces around the equals sign.

2. Step 2: Check the options for correct syntax

   greeting="Hello" uses no spaces and quotes the string correctly. The other options have invalid syntax.

3. Final Answer:

   greeting="Hello" -> Option A

4. Quick Check:

   No spaces around = and quotes needed [OK]

Hint: No spaces around = and use quotes for strings [OK]

Common Mistakes:

• Adding spaces around = causes syntax errors
• Forgetting quotes around strings with spaces
• Using wrong assignment symbols like : or <-

2. Which of the following correctly prints the value of the variable name in bash?

easy

A. echo name

B. echo $name

C. echo &name

D. echo %name

Solution

1. Step 1: Recall how to access variable values in bash

   Use the dollar sign ($) before the variable name to get its value.

2. Step 2: Evaluate each option

   echo $name uses $name correctly. echo name prints the literal word 'name'. The other options use invalid symbols.

3. Final Answer:

   echo $name -> Option B

4. Quick Check:

   Use $ to access variable value [OK]

Hint: Use $ before variable to print its value [OK]

Common Mistakes:

• Forgetting $ prints variable name, not value
• Using wrong symbols like & or %
• Confusing variable access with assignment

3. What will be the output of this bash script?

name="Alice"
echo "Hello, $name!"

medium

A. Hello, Alice!

B. Hello, $name!

C. Hello, name!

D. Hello, !

Solution

1. Step 1: Understand variable assignment and usage

   The variable name is assigned the string "Alice".

2. Step 2: Analyze the echo command with variable expansion

   The echo command uses double quotes, so $name is replaced by its value "Alice".

3. Final Answer:

   Hello, Alice! -> Option A

4. Quick Check:

   Variables expand inside double quotes [OK]

Hint: Variables expand inside double quotes, not single quotes [OK]

Common Mistakes:

• Expecting variable expansion inside single quotes
• Printing variable name literally without $
• Forgetting to assign variable before use

4. Identify the error in this bash script:

message = "Hi there"
echo $message

medium

A. Variable name is invalid

B. Quotes should be single quotes

C. Missing $ before variable in echo

D. Spaces around = cause syntax error

Solution

1. Step 1: Check variable assignment syntax

   In bash, no spaces are allowed around the equals sign when assigning variables.

2. Step 2: Analyze the given script

   The line message = "Hi there" has spaces around =, causing a syntax error.

3. Final Answer:

   Spaces around = cause syntax error -> Option D

4. Quick Check:

   No spaces around = in assignments [OK]

Hint: No spaces around = in variable assignment [OK]

Common Mistakes:

• Adding spaces around =
• Using wrong quotes type causes no error here
• Forgetting $ in echo prints variable name literally

5. You want to store a user's full name with spaces in a variable fullname and then print it. Which script correctly does this?

hard

A. fullname=John Doe
echo $fullname

B. fullname='John Doe'
echo fullname

C. fullname="John Doe"
echo $fullname

D. fullname=John_Doe
echo $fullname

Solution

1. Step 1: Assign string with spaces to variable

   Strings with spaces must be quoted to be assigned correctly in bash.

2. Step 2: Print the variable value

   Use echo $fullname to print the stored string value.

3. Final Answer:

   fullname="John Doe" echo $fullname -> Option C

4. Quick Check:

   Quote strings with spaces and use $ to print [OK]

Hint: Quote strings with spaces; use $ to print variable [OK]

Common Mistakes:

• Not quoting strings with spaces causes errors
• Printing variable name without $ prints literal text
• Using underscores instead of spaces changes the string