Variable assignment (no spaces around =) in Bash Scripting - Cheat Sheet & Quick Revision

Recall & Review

beginner

Why should there be no spaces around the = sign in bash variable assignment?

In bash, spaces around = are not allowed because bash treats spaces as separators. Spaces would cause bash to misinterpret the command, leading to errors.

beginner

What is the correct way to assign the value hello to a variable named greeting in bash?

The correct way is greeting=hello. No spaces should be before or after the = sign.

beginner

What happens if you write greeting = hello in bash?

Bash will try to run a command named greeting with arguments = and hello, causing an error because greeting is not a command.

intermediate

How do you assign a value with spaces to a variable in bash?

You put the value in quotes without spaces around =. For example: message="hello world".

beginner

Is this valid in bash? name= John

No, it is invalid because there is a space after =. The correct form is name=John.

Which of these is the correct way to assign the value 10 to a variable x in bash?

A x= 10

B x = 10

C x=10

D x =10

In bash, no spaces are allowed around the equals sign during variable assignment.

What will happen if you run var =value in bash?

A Assign '=value' to 'var'

B Assign 'value' to 'var'

C Syntax error

D Run command 'var' with argument '=value'

Bash treats 'var' as a command and '=value' as its argument because of the spaces.

How do you assign the string 'hello world' to a variable message in bash?

A message="hello world"

B message = "hello world"

C message= 'hello world'

D message=hello world

The value with spaces must be quoted and no spaces around '='.

Which is NOT a valid variable assignment in bash?

A Both B and D

B count =5

C count=5

D count= 5

Spaces around '=' are not allowed in bash variable assignments.

Why does bash require no spaces around '=' in variable assignment?

A Because '=' is a special operator that must be attached to the variable name

B Because spaces separate commands and arguments

C Because spaces cause syntax errors in all programming languages

D Because '=' is a reserved word

Bash uses spaces to separate commands and arguments, so spaces around '=' break the assignment.

Explain why spaces are not allowed around the equals sign in bash variable assignment.

Think about how bash reads commands and arguments.

Show how to correctly assign a string with spaces to a variable in bash.

Remember how to handle strings with spaces.

Practice

1. Which of the following is the correct way to assign the value hello to a variable named greet in bash?

easy

A. greet =hello

B. greet = hello

C. greet= hello

D. greet=hello

Solution

1. Step 1: Understand bash variable assignment rules

   Bash does not allow spaces around the = sign when assigning variables.

2. Step 2: Check each option for spaces

   Only greet=hello has no spaces around =. Options B, C, and D have spaces, which cause errors.

3. Final Answer:

   greet=hello -> Option D

4. Quick Check:

   No spaces around = means correct assignment [OK]

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

Common Mistakes:

• Adding spaces around = causes syntax errors
• Using quotes unnecessarily in simple assignments
• Trying to assign with spaces after =

2. Which of the following bash commands correctly assigns the value 42 to the variable num?

easy

A. num=42

B. num= 42

C. num =42

D. num = 42

Solution

1. Step 1: Identify spaces around the equal sign

   Bash requires no spaces around the = sign for variable assignment.

2. Step 2: Verify each option

   Only num=42 has no spaces around =. Others have spaces causing errors.

3. Final Answer:

   num=42 -> Option A

4. Quick Check:

   No spaces around = means correct syntax [OK]

Hint: Remember: no spaces around = in bash assignments [OK]

Common Mistakes:

• Leaving spaces around = causes syntax errors
• Confusing assignment with comparison operators
• Using quotes unnecessarily for numbers

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

name=John
echo $name

medium

A. name

B. Syntax error

C. John

D. $name

Solution

1. Step 1: Understand variable assignment and usage

   The variable name is assigned the value John without spaces around =.

2. Step 2: Understand echo with variable

   echo $name prints the value stored in name, which is John.

3. Final Answer:

   John -> Option C

4. Quick Check:

   Variable value printed, not variable name [OK]

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

Common Mistakes:

• Printing variable name instead of value
• Forgetting $ before variable in echo
• Adding spaces around = causing errors

4. Identify the error in the following bash script:

count =10
echo $count

medium

A. Spaces around = cause syntax error

B. Missing $ in echo

C. Variable name is invalid

D. No error, script runs fine

Solution

1. Step 1: Check variable assignment syntax

   The assignment count =10 has a space before =, which is not allowed in bash.

2. Step 2: Understand effect of spaces

   Spaces around = cause bash to treat count as a command, leading to syntax error.

3. Final Answer:

   Spaces around = cause syntax error -> Option A

4. Quick Check:

   No spaces around = means valid assignment [OK]

Hint: No spaces around = in assignment to avoid errors [OK]

Common Mistakes:

• Adding spaces around = in assignment
• Forgetting $ when printing variable
• Assuming variable names can have spaces

5. You want to store the current year in a variable year using the command date +%Y. Which of the following is the correct way to assign this output to year in bash?

hard

A. year = $(date +%Y)

B. year=$(date +%Y)

C. year= $(date +%Y)

D. year= '$(date +%Y)'

Solution

1. Step 1: Understand command substitution syntax

   To assign command output, use $(command) without spaces around =.

2. Step 2: Check each option for spaces and quotes

   year=$(date +%Y) has no spaces around = and uses correct command substitution syntax. Options A and C have spaces causing errors. year= '$(date +%Y)' uses quotes which are unnecessary and may cause literal assignment.

3. Final Answer:

   year=$(date +%Y) -> Option B

4. Quick Check:

   No spaces and correct command substitution [OK]

Hint: Use $(command) with no spaces around = for command output assignment [OK]

Common Mistakes:

• Adding spaces around = causes errors
• Using quotes around command substitution
• Forgetting to use $( ) for command output