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Making server requests using PowerShell

jordanholtdev profile image Jordan Holt Originally published at blog.jordanholt.dev on ・6 min read

In this post I’ll show you how to make server requests using PowerShell cmdlets. While you can use curl directly from Cmd or PowerShell inWindows 10 this article will focus on using PowerShell cmdlets Invoke-WebRequestand Invoke-RestMethod and not thedifferences between curl.

Make sure to check out my PowerShell for developers crash course if you’d like to refresh on some of the basics.

Requesting Data from a REST API

Let’s first have a look at how we can get data from an API using Invoke-WebRequest. I’ll be usingthe jsonplaceholder site as an example to get started.

You can use Invoke-WebRequest to make HTTP or HTTPS requests. Simply provide a value to the -Uri parameter.

# these are the same 
Invoke-WebRequest -Uri "https://jsonplaceholder.typicode.com/users/1"
Invoke-WebRequest "https://jsonplaceholder.typicode.com/users/1"

Here is the response:

StatusCode : 200
StatusDescription : OK
Content : {
                      "id": 1,
                      "name": "Leanne Graham",
                      "username": "Bret",
                      "email": "Sincere@april.biz",
                      "address": {
                        "street": "Kulas Light",
                        "suite": "Apt. 556",
                        "city": "Gwenborough",
                        "zipco…
                    }
RawContent : HTTP/1.1 200 OK
                    Date: Fri, 28 Aug 2020 22:45:18 GMT
                    Connection: keep-alive
Headers : {[Date, System.String[]], [Connection, System.String[]], [Set-Cookie, System.String[]], [X-Powered-By, System.String[]]…}
Images : {}
InputFields : {}
Links : {}
RawContentLength : 509
RelationLink : {}

That was pretty simple right? All we had to do was specify a -Uri parameter value and Invoke-WebRequest requested the data and performed somebasic parsing of the response. You’ll see we not only get the actual content of the web page but also the associated metadata.

Because PowerShell natively parses the response data, if you wanted to see a single response property you could do something like this:

# this will only display the content of response
(Invoke-WebRequest "https://jsonplaceholder.typicode.com/users/1").Content

You’ll notice how the command and -Uri parameter are enclosed in parentheses () which allows you to access the objects properties using dot notation.

Now let’s request the same data using the Invoke-RestMethod cmdlet.

Invoke-RestMethod "https://jsonplaceholder.typicode.com/users/1"

Here’s the response:

id : 1
name : Leanne Graham
username : Bret
email : Sincere@april.biz
address : @{street=Kulas Light; suite=Apt. 556; city=Gwenborough; zipcode=92998-3874; geo=}
phone : 1-770-736-8031 x56442
website : hildegard.org
company : @{name=Romaguera-Crona; catchPhrase=Multi-layered client-server neural-net; bs=harness real-time e-markets}

Notice how the response has been automatically converted from JSON to a PowerShell object and does not include the metadata.The biggest difference between Invoke-WebRequest is that Invoke-RestMethod automatically converts JSON and XML response data into PowerShell objects, while Invoke-WebRequestis best for handling HTML data.

Check out this article by Billy York which goes deeper into the differences.

Saving the response body to a file

You can easily save the response body to a specified file by using the -Outfile parameter. In this example we’ll save the data to a file called output.json. PowerShell will create this file in the current location if it does not already exist.

# the -Outfile parameter is available on both cmdlets
Invoke-RestMethod "https://jsonplaceholder.typicode.com/users/1" -Outfile output.json
Invoke-WebRequest "https://jsonplaceholder.typicode.com/users/1" -Outfile output.json

Making a POST request

Here’s how you can make a POST request using Invoke-RestMethod. You can also use Invoke-WebRequest but for the following examples we’ll be using Invoke-RestMethod.

In this examples you’ll be using a couple of variables in this command. One called $url which will stores endpoint and another called $Body which will store the body of the POST request.

$url = "https://jsonplaceholder.typicode.com/posts"
$Body = @{
    id = 1
    userId = 1
    title = "sending a POST request"
    body = "Lorem ipsum dolor sit amet, consectetur"
}
Invoke-RestMethod -Method "Post" -Uri $url -Body $Body

By default both Invoke-RestMethod and Invoke-WebRequest set the content type of the body to application/x-www-form-urlencoded. You can easily specify a different content type like this:

## continuing the example above
Invoke-RestMethod -Method "Post" -Uri $url -Body $Body -ContentType application/json

Scrape links off a web page

Invoke-WebRequest makes it really easy to extract all the links from a web page. Because this cmdlet automatically parses the HTML all we need to do is indicate we only want the <a> tags from the page. Notice again that the cmdlet and parameter are wrapped in parentheses.

We’ll use the GitHub homepage as an example.

(Invoke-WebRequest "https://github.com/").Links.Href

GitHub Links Image

Tracking GitHub issues

In this example we’ll be using the GitHub API and the Invoke-RestMethod cmdlet to list all the open issues for the React-Native repository. Taking it a bit further you could also filter the results to your specific needs, perhaps you’re only interested in seeing open issues that contain specific keywords.

First we can get a list of all the endpoint categories that their REST API supports.

# this will return a list of available endpoints
Invoke-RestMethod "https://api.github.com"

The one that should fit our needs is https://api.github.com/repos/{owner}/{repo}. The owner is facebook and the repo is react-native,we’ll also be querying for any open issues.

$url = "https://api.github.com/repos/facebook/react-native/issues?state=open"
$site = Invoke-RestMethod $url

Now that you have a list of open issues you can refine the results even further. In this example let’s only extract results that contain the keyword iOS. You can use the -Match comparison operator to search for matches.

# our keyword will be iOS
$keyword = 'ios'
$site -Match $keyword

We’ll go ahead and save all the matching results in a variable named $AllMatches.

$AllMatches = $site -Match $keyword

Now we can use dot notation to access the specific object properties you might need.

# list all the titles from the search
$AllMatches.title

Here we see all titles of all the open issues that contain our defined keyword:

Local images not rendered on iOS physical device for release build
Metro-bundler error: Module `@babel/runtime/helpers/interopRequireDefault` does not exist in the Haste module map
Change ScrollView.scrollIndicatorInsets to not automatically add safe area on iOS 13
Bug in TextInput's text style in android, when the text's style in changed conditionally
false trackColor prop does not work for Switch component on iOS
Fix duplicate accessibilityLabels on iOS
Double slashes instead of tripple
React-Native "react-native": "0.62.2" is not working on Android - 9.
iOS use_frameworks! broken in v0.63.2
iOS Linking getInitialURL() Cannot read, copy or use the file in the url
Update Flipper
Cannot animate shadowOffset

Perhaps it would be helpful to have the title and created_at properties written to a file so we can email them or add them toa database. You can iterate over $AllMatches and extract specific properties that can then be saved to a file.

$IssueList = forEach($item in $AllMatches) { Write-Output $item.created_at, $item.title}
$IssuesList | Out-File -Path .\IssueReport.txt

You could continue with this example and begin to automate the request to update daily, email a team member or really anything that mightbe helpful to monitor issues.

Wrap up

In this we saw how we can use Invoke-WebRequest and Invoke-RestMethod to make server requests, including POST requests. As well asextract links from a web page and interact with the GitHub API to track issues with a specific repository and search keyword.

There are many many more options, scenarios and concepts about server requests, parsing and Invoke-WebRequest and Invoke-RestMethod thatwere not mentioned here so make sure to have a look at the official docsto learn more.

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