Compare-Object for differences in PowerShell - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of Compare-Object with default SideIndicator?

Given these two arrays:

$a = 1,2,3,4
$b = 3,4,5,6
Compare-Object $a $b

What is the output?

PowerShell

$a = 1,2,3,4
$b = 3,4,5,6
Compare-Object $a $b

A

@{InputObject=1; SideIndicator=>=}
@{InputObject=2; SideIndicator=>=}
@{InputObject=5; SideIndicator=<=}
@{InputObject=6; SideIndicator=<=}

B

@{InputObject=1; SideIndicator=<=}
@{InputObject=2; SideIndicator=<=}
@{InputObject=5; SideIndicator=>=}
@{InputObject=6; SideIndicator=>=}

C

@{InputObject=3; SideIndicator=<=}
@{InputObject=4; SideIndicator=<=}
@{InputObject=5; SideIndicator=>=}
@{InputObject=6; SideIndicator=>=}

D

@{InputObject=1; SideIndicator=<=}
@{InputObject=2; SideIndicator=<=}
@{InputObject=3; SideIndicator=>=}
@{InputObject=4; SideIndicator=>=}

💡 Hint

SideIndicator <= means the item is only in the first array; >= means only in the second.

Compare-Object compares two collections and shows differences. Items only in $a have SideIndicator <=, items only in $b have >=. Here, 1 and 2 are only in $a, 5 and 6 only in $b.

💻 Command Output

intermediate

What does -IncludeEqual parameter do in Compare-Object?

Given:

$a = 'apple','banana','cherry'
$b = 'banana','cherry','date'
Compare-Object $a $b -IncludeEqual

What output will this produce?

PowerShell

$a = 'apple','banana','cherry'
$b = 'banana','cherry','date'
Compare-Object $a $b -IncludeEqual

A

@{InputObject=apple; SideIndicator=<=}
@{InputObject=banana; SideIndicator==}
@{InputObject=cherry; SideIndicator==}
@{InputObject=date; SideIndicator=>=}

B

@{InputObject=apple; SideIndicator=<=}
@{InputObject=banana; SideIndicator=<=}
@{InputObject=cherry; SideIndicator=<=}
@{InputObject=date; SideIndicator=>=}

C

@{InputObject=apple; SideIndicator=>=}
@{InputObject=banana; SideIndicator=<=}
@{InputObject=cherry; SideIndicator=<=}
@{InputObject=date; SideIndicator=>=}

D

@{InputObject=apple; SideIndicator==}
@{InputObject=banana; SideIndicator==}
@{InputObject=cherry; SideIndicator==}
@{InputObject=date; SideIndicator==}

💡 Hint

SideIndicator == means the item is in both collections.

With -IncludeEqual, Compare-Object shows items that are the same in both collections with SideIndicator ==. Items unique to $a have <=, unique to $b have >=.

📝 Syntax

advanced

Which Compare-Object command correctly compares two custom objects by a property?

You have two arrays of objects:

$a = @(@{Name='John'; Age=30}, @{Name='Jane'; Age=25})
$b = @(@{Name='John'; Age=31}, @{Name='Jake'; Age=25})

Which command compares them by the 'Name' property only?

A Compare-Object $a $b -Property Name

B Compare-Object $a $b -Property Age

C Compare-Object $a $b -IncludeEqual

D Compare-Object $a $b -PassThru

💡 Hint

Use -Property to specify which property to compare.

The -Property parameter tells Compare-Object to compare objects based on that property only. Here, comparing by 'Name' shows differences ignoring 'Age'.

💻 Command Output

advanced

What is the output count of Compare-Object when comparing identical arrays without -IncludeEqual?

Given:

$a = 1,2,3
$b = 1,2,3
Compare-Object $a $b

How many objects does this command output?

PowerShell

$a = 1,2,3
$b = 1,2,3
Compare-Object $a $b

A 1

B 3

C 0

D 6

💡 Hint

Without -IncludeEqual, identical items are not shown.

Compare-Object without -IncludeEqual only shows differences. Since arrays are identical, no differences exist, so output count is zero.

🚀 Application

expert

How to find items only in the second array using Compare-Object?

You want to get only the items that exist in $b but not in $a.

$a = 'red','green','blue'
$b = 'green','blue','yellow','black'

Which command correctly outputs only 'yellow' and 'black'?

PowerShell

$a = 'red','green','blue'
$b = 'green','blue','yellow','black'

A Compare-Object $b $a | Where-Object { $_.SideIndicator -eq '=>' } | ForEach-Object { $_.InputObject }

B Compare-Object $a $b | Where-Object { $_.SideIndicator -eq '<=' } | ForEach-Object { $_.InputObject }

C Compare-Object $b $a | Where-Object { $_.SideIndicator -eq '<=' } | ForEach-Object { $_.InputObject }

D Compare-Object $a $b | Where-Object { $_.SideIndicator -eq '=>' } | ForEach-Object { $_.InputObject }

💡 Hint

SideIndicator '=>' means item is only in the second collection passed to Compare-Object.

Compare-Object $a $b outputs items unique to $a with '<=' and unique to $b with '=>'. Filtering SideIndicator '=>' gives items only in $b.