Ezine 206 – PowerShell’s Comparison Operators

PowerShell’s Comparison Operators

For PowerShell newbies one of the strangest comparison operators is -eq.  While you still need the equals sign ‘=’ for declaring variables, in most other cases you need PowerShell’s -eq.  Also, for not equal, use the -ne operator.  Once you warm to this theme of dash followed by initial letter, then -gt (greater than) or -lt (less than) will seem a logical continuation.  Consequently, abandon > < and employ -gt or -lt instead.

Topics for Comparison Operators in PowerShell

• This Week’s Secret
• PowerShell’s -eq in a ‘Where clause’
• Example of PowerShell’s -eq and -ne Operators
• PowerShell’s Greater Than Comparison Operator -gt

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This Week’s Secret

My problem is not with -eq (equals) but with -ne, not equal.  I have an overwhelming urge to use -neq instead of plain -ne.  Once I overcome this foible employing PowerShell’s comparison family of operators is straight forward.

Example of PowerShell’s -eq and -ne Operators

The point of the following real-life script is to test for internet connectivity.  If there is none, then PowerShell can cure this particular browser problem by restarting the dnscache service.

Learning Points

Note 2: We employ an ‘if’ statement to act upon the output of test-connection.

Note 3: Remember that instead of an equal sign (=), PowerShell uses -eq.  One benefit is that it’s easy to use the negative -ne (not equal).

-Eq Operator with .txt File Extensions

Note 4: For the sake of completeness, there is also -ceq where ‘c’ means case-sensitive.

Example of PowerShell’s Greater Than Comparison Operator -gt

In PowerShell, greater than is abbreviated to -gt.  Observe how both -gt and lt (less than) are preceded by a dash.

Learning Points

Note 5:  The point of the above comparison example is to find long files; to be precise to list filenames greater than 254 characters.

Note 6:  As 254 is a pure number it needs no quotes.

Note 7:  Be aware that if you want to get this example to work you would need a file containing the list of filenames that you wish to check.  Also be prepared to change the value of $FileSource.

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Example of PowerShell’s -eq and -ne Operators

The point of the following real-life script is to test for internet connectivity.  If there is none, then PowerShell can cure this particular browser problem by restarting the dnscache service.

Learning Points

Note 2: We employ an ‘if’ statement to act upon the output of test-connection.

Note 3: Remember that instead of an equal sign (=), PowerShell uses -eq.  One benefit is that it’s easy to use the negative -ne (not equal).

-Eq Operator with .txt File Extensions

Note 4: For the sake of completeness, there is also -ceq where ‘c’ means case-sensitive.

Example of PowerShell’s Greater Than Comparison Operator -gt

In PowerShell, greater than is abbreviated to -gt.  Observe how both -gt and lt (less than) are preceded by a dash.

Learning Points

Note 5:  The point of the above comparison example is to find long files; to be precise to list filenames greater than 254 characters.

Note 6:  As 254 is a pure number it needs no quotes.

Note 7:  Be aware that if you want to get this example to work you would need a file containing the list of filenames that you wish to check.  Also be prepared to change the value of $FileSource.

PowerShell’s Less Than Comparison Operator -lt

Just as -eq has an opposite in -ne, so -gt (greater than) has a mirror image in -lt (less than).  In other scripting languages these would be represented by > and < symbols, however PowerShell uses the dash then an abbreviation of the comparison operator, thus -lt.

Speaking of > and <, they have >= and <= to represent greater than or equal and less than or equal.  In PowerShell such concepts involving equal are represented by -ge and -le, where ‘e’ stands for equal.

Here is an example not of -lt, but -le meaning less than or equal.  What it does is calculate and display the 12 times table.

Summary of PowerShell’s Comparison Operators

PowerShell uses the equals sign ‘=’ for declaring variables, but for genuine comparison operations you need -eq.  Also, for not equal, use the -ne operator.  When comparing greater than or less than, it is logical to use -gt and -lt and not > or <.

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See more Microsoft PowerShell tasks:

• PowerShell Home   • Shell Application   • New-Object   • PowerShell Add Printer   • PowerShell -com

• PowerShell Logon Script  • Map Network Drive  • PowerShell Create Shortcut  • Free CSV Import Tool

• Invoke-Expression   • Invoke-Command   • Invoke-Item   • PowerShell Expression v Command Mode

Please email me if you have a better example script. Also please report any factual mistakes, grammatical errors or broken links, I will be happy to correct the fault.