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+--- Thread: How to check if file has valid JSON syntax in Powershell (/Thread-How-to-check-if-file-has-valid-JSON-syntax-in-Powershell)
How to check if file has valid JSON syntax in Powershell - pulverable380 - 07-21-2023
I am trying to write a powershell script that reads a file and prints "true" if it is a valid JSON file. I am using Powershell v3.0 and this is what I have right now :
$text = Get-Content .\filename.txt -Raw
$powershellRepresentation = $text | ConvertFrom-Json
How do I check the return code? I mean I want something like this :
if(file not a JSON file){
Write-Host "not JSON"
}
else{
Write-Host "True"
}
RE: How to check if file has valid JSON syntax in Powershell - guanabara288 - 07-21-2023
I don't think that it exists an other solution than catching the exception using `ConvertFrom-Json`.
RE: How to check if file has valid JSON syntax in Powershell - hoised152758 - 07-21-2023
ConvertFrom-JSON would work but only for a JSON object < 2MB in size.
For higher you can use JavaScriptSerializer class
try
{
$jsser = New-Object System.Web.Script.Serialization.JavaScriptSerializer
$jsser.MaxJsonLength = $jsser.MaxJsonLength * 10
$jsser.RecursionLimit = 99
$outObject = $jsser.DeserializeObject($json)
}
catch
{
Write-Host "Error converting $text to JSON"
}
RE: How to check if file has valid JSON syntax in Powershell - clothesline508 - 07-21-2023
If you encounter this question and can use PowerShell 6 or later, there is now a Test-Json cmdlet. It can also not just validate that it's valid JSON, but that it conforms to a particular JSON schema using the `-Schema` param.
## Example ##
```PowerShell
$isValid = Get-Content .\filename.txt -Raw | Test-Json
if($isValid){
Write-Host "not JSON"
}
else{
Write-Host "True"
}
```
## ARM Template Warning ##
A note for users looking to validate an ARM template via `-Schema` (I can't imagine a more perfect use case). At the time of writing, there are one or more bugs in the underlying library `Test-Json` uses for validation, NJsonSchema, and it is not possible to validate an ARM template.
### GitHub Issues ###
* [PowerShell Issue #9560](
[To see links please register here]
)* [NJsonSchema Issue #588](
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)RE: How to check if file has valid JSON syntax in Powershell - heliocentricity631167 - 07-21-2023
**UPDATE 2021: PowerShell 6 and newer versions**
PowerShell 6 brings a brand new `Test-Json` cmdlet. [Here is the reference][1].
You can simply pass the raw file content directly to the `Test-Json` cmdlet.
```
$text = Get-Content .\filename.txt -Raw
if ($text | Test-Json) {
$powershellRepresentation = ConvertFrom-Json $text -ErrorAction Stop;
Write-Host "Provided text has been correctly parsed to JSON";
} else {
Write-Host "Provided text is not a valid JSON string";
}
```
**PowerShell 5 and earlier versions**
There is no `Test-Json` cmdlet in these versions, so the best way is to put your `ConvertFrom-Json` cmdlet inside a `try ... catch` block
try {
$powershellRepresentation = ConvertFrom-Json $text -ErrorAction Stop;
$validJson = $true;
} catch {
$validJson = $false;
}
if ($validJson) {
Write-Host "Provided text has been correctly parsed to JSON";
} else {
Write-Host "Provided text is not a valid JSON string";
}
[1]:
[To see links please register here]
RE: How to check if file has valid JSON syntax in Powershell - verboten147 - 07-21-2023
ConvertFrom-Json shd be the appropriate way to go.
Test-Json unfortunately has alot of known unsupported JSON Types.
I.E. it cannot parse Json-Arrays or Primitives properly leading to falsely assuming it has wrong JSON-Syntax.