how to format json string for aws with powershell - json

Question

i want to send an event to aws via a cli command in a powershell script. Here is the Json i need to send to the eventbridge:
[
{
"Sensor":"{\"id\":\"880/2021-04-13\",\"attributes\":\"green\",\"Name\":\"SensorGreen\",\"state\":\"SUCCEEDED\"}",
"Source":"google.com"
}
]
Thats what a tried in powershell:
$json='[{"Sensor":"{\"id\":\"880/2021-04-13\",\"attributes\":\"green\",\"Name\":\"SensorGreen\",\"state\":\"SUCCEEDED\"}","Source":"google.com"}]'|ConvertTo-Json -Compress
aws events put-events --entries $json --region "eu-central-1"
That does not work. I even tried to write it to a json file and read it and send it from the file but it doesnt work. It somehow leads to too many "\" slashes or no slashes for my "Sensor" where it is necessary. I even tried to create a object and just convert the Sensor object to Json and then the whole object again to have the escaping, but it is not working.
EDIT:
i tried also this as mentioned in the answer:
$RequestObject = [pscustomobject] #(#{
Sensor = [pscustomobject] #{
id = "880/2021-04-13"
attribute = "green"
Name = "SensorGreen"
state = "SUCCEEDED"
}
Source = "google.com"
})
$RequestObject.Get(0).Sensor=$RequestObject.Get(0).Sensor | ConvertTo-Json -Compress
$Json = $RequestObject | ConvertTo-Json -Compress
aws events put-events --entries $Json --region "eu-central-1"
i included the #() to have an array and converted the sensor object twice to json to include the slashes. but the result is:
Error parsing parameter '--entries': Invalid JSON: Expecting property name enclosed in double quotes: line 1 column 2 (char 1)
if i use the command line interface only with the aws command and put the object directly into the command, then it works.. but the powershell does not.

Answer 1

You're passing a JSON string to an external program (aws)
Irrespective of how you constructed that string - directly as a string, or from an object / hashtable via ConvertTo-Json - as of PowerShell 7.1 - manual escaping of embedded " as \" is required, which, in turn requires escaping the preexisting \ preceding the embedded " as \\.
Note: None of this should be necessary, but due to a long-standing bug in PowerShell is - see this answer for details.
PowerShell Core 7.2.0-preview.5 now includes experimental feature PSNativeCommandArgumentPassing with an attempted fix, but, unfortunately, it looks like it will lack important accommodations for high-profile CLIs on Windows - see this summary from GitHub issue #15143. However, it would fix calls to aws.exe, the Amazon Web Services CLI.
# The JSON string to be passed as-is.
$json = #'
[
{
"Sensor":"{\"id\":\"880/2021-04-13\",\"attributes\":\"green\",\"Name\":\"SensorGreen\",\"state\":\"SUCCEEDED\"}",
"Source":"google.com"
}
]
'#
# Up to at least PowerShell 7.1:
# Manually perform the required escaping, to work around PowerShell's
# broken argument-passing to external programs.
# Note:
# -replace '\\', '\\' *looks* like a no-op, but replaces each '\' with '\\'
$jsonEscaped = $json -replace '\\', '\\' -replace '"', '\"'
# Now pass the *escaped* JSON string to the aws CLI:
aws events put-events --entries $jsonEscaped --region "eu-central-1"

Answer 2

ConvertTo-Json is for converting objects in PowerShell, not a string that you have tried to already write in Json. Your $Json variable produces this.
"[{\"Sensor\":\"{\\\"id\\\":\\\"880/2021-04-13\\\",\\\"attributes\\\":\\\"green\\\",\\\"Name\\\":\\\"SensorGreen\\\",\\\"state\\\":\\\"SUCCEEDED\\\"}\",\"Source\":\"google.com\"}]"
If you want to create the object in PowerShell and convert it to Json, then you can do this.
$RequestObject = [pscustomobject] #{
Sensor = [pscustomobject] #{
id = "880/2021-04-13"
attribute = "green"
Name = "SensorGreen"
state = "SUCCEEDED"
}
Source = "google.com"
}
$Json = $RequestObject | ConvertTo-Json -Compress
aws events put-events --entries $Json --region "eu-central-1"
Your Json will look like this if you print your variable out.
{"Sensor":{"id":"880/2021-04-13","attribute":"green","Name":"SensorGreen","state":"SUCCEEDED"},"Source":"google.com"}
Which I think is like the Json that the command is expecting. Not entirely sure why you need the strings escaping or the array. Here it is uncompressed.
{
"Sensor": {
"id": "880/2021-04-13",
"attribute": "green",
"Name": "SensorGreen",
"state": "SUCCEEDED"
},
"Source": "google.com"
}
Just noticed the powershell-2.0 tag. If you are using it, then you should do this instead to create your Json.
$Sensor = New-Object psobject -Property #{
id = "880/2021-04-13"
attribute = "green"
Name = "SensorGreen"
state = "SUCCEEDED"
}
$RequestObject = New-Object psobject -Property #{
Sensor = $Sensor
Source = "google.com"
}
$Json = $RequestObject | ConvertTo-Json -Compress
EDIT
If you absolutely must escape the strings in that way and have a single item array, then you should just pass the Json that you have written in your answer without any further conversion.
$json='[{"Sensor":"{\"id\":\"880/2021-04-13\",\"attributes\":\"green\",\"Name\":\"SensorGreen\",\"state\":\"SUCCEEDED\"}","Source":"google.com"}]'
If you want to make PowerShell do that for you then you would need to perform some string replacement on the Sensor object first.
PowerShell 2.0
$Sensor = New-Object psobject -Property #{
id = "880/2021-04-13"
attribute = "green"
Name = "SensorGreen"
state = "SUCCEEDED"
}
$SensorJson = $Sensor | ConvertTo-Json -Compress
$SensorJson.Replace("`"","\`"")
$RequestObject = New-Object psobject -Property #{
Sensor = $SensorJson
Source = "google.com"
}
$Json = $RequestObject | ConvertTo-Json -Compress
PowerShell 3.0+
$Sensor = [pscustomobject] #{
id = "880/2021-04-13"
attribute = "green"
Name = "SensorGreen"
state = "SUCCEEDED"
}
$SensorJson = $Sensor | ConvertTo-Json -Compress
$SensorJson.Replace("`"","\`"")
$RequestObject = [pscustomobject] #{
Sensor = $SensorJson
Source = "google.com"
}
$Json = $RequestObject | ConvertTo-Json -Compress
Then your AWS command
# Add the array around the compressed Json string.
aws events put-events --entries "[$Json]" --region "eu-central-1"
"[$Json]" prints
[{"Sensor":"{\"id\":\"880/2021-04-13\",\"attribute\":\"green\",\"Name\":\"SensorGreen\",\"state\":\"SUCCEEDED\"}","Source":"google.com"}]