Comparison and Logical Operators¶

Comparison and logical operators allow a script to evaluate conditions and make decisions. Comparison operators check whether two values match a specific relationship (equal, greater than, less than, etc.). Logical operators combine multiple conditions into a single expression. These operators are used in if statements, loops, filters, and anywhere a script needs to decide what to do next.

1. Comparison Operators¶

Comparison operators evaluate two values and return a boolean ($true or $false).

All comparison operators in PowerShell start with a hyphen (-).

1.1 Equality and inequality¶

5 -eq 5      # True
5 -ne 3      # True
5 -eq 3      # False

• eq means “equal to”.
• ne means “not equal to”.

1.2 Greater than / less than¶

10 -gt 5     # True
10 -lt 5     # False
5  -le 5     # True
10 -ge 10    # True

• gt = greater than
• lt = less than
• ge = greater than or equal
• le = less than or equal

1.3 String comparisons¶

PowerShell compares strings case‑insensitively by default:

"hello" -eq "HELLO"   # True

Case‑sensitive versions use a c prefix:

"hello" -ceq "HELLO"  # False

1.4 Pattern matching¶

PowerShell supports wildcard matching:

"PowerShell" -like "Power*"     # True
"PowerShell" -notlike "Test*"   # True

• like uses and ? wildcards.

Regular expression matching:

"abc123" -match "\d+"     # True
"hello"  -match "\d+"     # False

• match uses full regex syntax.

2. Logical Operators¶

Logical operators combine multiple boolean expressions into one.

2.1 and¶

Both conditions must be true.

($age -gt 18) -and ($age -lt 65)

If $age is between 19 and 64, the result is True.

2.2 or¶

At least one condition must be true.

($color -eq "red") -or ($color -eq "blue")

This is true if $color is "red" or "blue".

2.3 not¶

Negates a condition.

-not ($value -eq 10)

Equivalent to:

$value -ne 10

2.4 Combining multiple operators¶

PowerShell evaluates expressions left‑to‑right, but parentheses make the logic explicit:

($score -ge 80) -and (($role -eq "admin") -or ($role -eq "manager"))

Explanation:

• The score must be 80 or higher.
• The role must be either "admin" or "manager".

3. Using comparison and logical operators in real code¶

3.1 Filtering values in an array¶

$numbers = 1, 5, 10, 15, 20

$large = $numbers | Where-Object { $_ -gt 10 }

Explanation:

• Each number is passed to the script block.
• $_ is the current number.
• Only numbers greater than 10 are kept.
• $large becomes 15, 20.

3.2 Validating user input¶

$age = Read-Host "Enter your age"

if ([int]$age -ge 18 -and [int]$age -le 65) {
    "Valid age range."
} else {
    "Out of range."
}

Explanation:

• The input is cast to an integer.
• The script checks whether the age is between 18 and 65.
• The correct message is printed.

3.3 Checking multiple conditions¶

$name = "Alice"
$loggedIn = $true

if ($name -eq "Alice" -and $loggedIn) {
    "Access granted."
}

Explanation:

• The name must be "Alice".
• $loggedIn must be $true.
• Both conditions must be satisfied.

3.4 Using pattern matching¶

$files = "report1.txt", "image.png", "report2.txt"

$reports = $files | Where-Object { $_ -like "report*.txt" }

Explanation:

• The wildcard pattern matches any string starting with "report" and ending with .txt.
• $reports becomes "report1.txt", "report2.txt".