Converting CSV data to datetime format

Question

I'm still learning Powershell and in order to complete an assignment I need to convert written data in CSV files to a powershell accepted datetime format.

The dates in the CSV format are written as: 1-1-2014.

In order to convert them I found out (through a bit of brute force) that I can use the following code:

$Files = gci $Source\*.csv 

$Data = Import-CSV $Files -Delimiter ";"

$Data | ForEach-Object { $_.Time = $_.Time -as [datetime] 
$_ 
}

However, it would seem to me that this should work as well when written as follows:

$Data | ForEach-Object { $_.Time = $_.Time -as [datetime] $_ }

When I run it like that it returns a bunch of errors.

The $_ after [datetime] I also only added because a colleague used that in his functions, I don't really understand why it has to be put there, and why it needs to be put on a new line. Could anyone explain? If there is a different/better way to convert CSV data to a datetime format I'd be interested in hearing those as well, thanks in advance!

Use ; in place of line breaks as a statement terminator. ... -as [datetime];$_ — Mathias R. Jessen
– Mathias R. Jessen, Commented Mar 3, 2022 at 13:08
$_.Time = is updating the object's Time property and produces no output, $_ after that assignment is needed to produce the output of the updated object. — Santiago Squarzon
– Santiago Squarzon, Commented Mar 3, 2022 at 13:11

Mathias R. Jessen · Accepted Answer · 2022-03-03 13:12:01Z

2

The first (multi-line) version works because PowerShell interprets a line-break after a complete statement as a terminator - it knows that $_ is a separate statement from $_.Time = $_.Time -as [datetime].

To place multiple separate statements on a single line, you'll have to use a semicolon ; to separate them:

$Data | ForEach-Object { $_.Time = $_.Time -as [datetime]; $_ }

answered Mar 3, 2022 at 13:12

Mathias R. Jessen

178k13 gold badges175 silver badges234 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Ingo van den Bersselaar Over a year ago

That answers one question, thanks! But why is it even neccessary to add $_ after the [datetime]? Why isn't { $_.Time = $_.Time -as [datetime] } just enough?

Mathias R. Jessen Over a year ago

@IngovandenBersselaar Because you're just modifying the value of a property - why would that produce any output?

Ingo van den Bersselaar Over a year ago

Ah, I think I get it, I figured if I modify the value I can call on it later and it accepts the value as a datetime format value, but adding the $_ afterwards does that part if I understand correctly.

Mathias R. Jessen Over a year ago

No, $_ simply outputs the object that we received as input (and then modified). When you see a bare value expression like $_, PowerShell interprets it as Write-Output $_ - you're simply telling ForEach-Object: output the input object after modifying it.

Collectives™ on Stack Overflow

Converting CSV data to datetime format

1 Answer 1

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related