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.
At first using -ne for 'not equal' also seems odd, but once you warm to this theme of dash followed by initial letters, then -gt (greater than) or -lt (less than) will seem
a logical continuation.
Consequently, abandon > < and employ -gt or -lt instead.
# PowerShell script to list DLLs under system32 folder
$Dir = Get-Childitem C:\windows\system32 -recurse $List =
$Dir | where {$_.extension -eq ".dll"} $List | Format-Table Name,
CreationTime -auto
Learning Points
Note 1: About the only thing that could go wrong with
the
-eq syntax is whether to put the comparison object in single or double
quotes. The difference is that "Double Quotes" expands any variables;
whereas 'single quotes' are treated as literals. In this example either
".dll" or '.dll' would achieve the desired listing.
See more about quotes here.
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.
# PowerShell Script to Test An Internet Connection $DNS =
(test-connection www.google.com -quiet) if($DNS -eq "True")
{Write-Host "Internet Available"} ElseIf($DNS -ne "True")
{Restart-Service dnscache}
Learning Points
Note 2: We employ an 'if' statement to act upon the
output of test-connection.
Note 3: Remember that instead of an equal sign (=), PowerShell uses -eq.
One benefit is that it's easy to use the negative -ne (PowerShell's not equal).
-Eq Operator with .txt File Extensions
# PowerShell Comparison Operator -eq in Foreach Loop "File Name " + "`t Size" +"`t Last Accessed" foreach ($file in Get-Childitem) {if ($file.extension
-eq ".txt") { $file.name + "`t " +$file.length + "`t " + $file.LastAccessTime } }
Note 4: For the sake of completeness, there is also
-Ceq where 'c' means case-sensitive.
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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 either need a D: drive, or else 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.
for ( $i = 12; $i -le 144; $i+=12 ) { $i }
Guy
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Normally all these comparison operators are not case sensitive.
However, to select on the precise UPPER or Proper case precede the
operator name with a "c". For example, "-cmatch"
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 <.
If you like this page then please share it with your friends
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.
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