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I have an Azure function and I am trying to save a .xlsx file to a temporary folder. My code works locally, but when I publish to Azure I get an error message.

string projectDirectory = Directory.GetParent(Environment.CurrentDirectory).Parent.Parent.FullName + @"\temp\";
string tempFilename = "abc.xlsx";
string pathTradeRecFile = Path.Combine(projectDirectory, tempFilename);

My error message. <--- Access to the path 'C:\Program Files (x86)\SiteExtensions\temp\abc.xlsx' is denied.

Can someone please tell me how I can save this file somewhere? I made a folder in my structure named "temp" as one possible solution, but I can't seem to access it.

Any help would be greatly appreciated!!

silent
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solarissf
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4 Answers4

7

Please do not use something like Environment.CurrentDirectory in Azure Functions (or actually, just anywhere) to get a temp folder. Instead use the .NET-native method to do so:

Path.GetTempPath()

So ideally use something like this:

string pathTradeRecFile = Path.Combine(Path.GetTempPath(), Path.GetRandomFileName() + ".xlsx");
silent
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  • thank you silent, I actually just came across this and it seems to be working. how do I visually look at this folder in something like Kudu? meaning any idea where it physically puts it? – solarissf Jan 14 '21 at 15:02
  • just log the generated path? But not sure if you can really see it - at least not for long. that's the whole point of it being temporary ;) and latest, when the function instance gets recycled it will be cleared – silent Jan 14 '21 at 15:36
  • if you want to keep the files for debugging etc, you need to write them out to Blob storage etc. – silent Jan 14 '21 at 15:36
  • If that's the case. Do you think I should worry about deleting the file or it will automatically be done? – solarissf Jan 14 '21 at 15:37
  • it will be done automatically. but if you generate a lot of those in a short time, potentially on the same Function instance, it is probably a good idea to quickly delete it at the end of your function run – silent Jan 14 '21 at 15:38
1

My apologies, but I did not get your intention to save file in Azure storage file system? However if azure function allows to save file locally then you should use Directory.GetCurrentDirectory(); which resolves to D:\home\site\wwwroot path.

Coming to my initial point, if you have a requirement to save the file locally to finally upload at persistent storage like Azure Blob then you don't need to save file locally at file system; you can use MemoryStream as shown in below code to upload the content at Azure blob

using (var ms = new MemoryStream())  
{ 
     using (StreamWriter writer = new StreamWriter(ms))
     { 
            writer.Write(obj);   // here obj represents the file data which you need to upload
            writer.Flush();  
            ms.Position = 0 
     };  
     await blob.UploadFromStreamAsync(ms);  
}
user1672994
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0

Environment variables as seen by an Azure Function aren't the same as the overall OS Environment variables. See this page for how to configure them: https://learn.microsoft.com/en-us/azure/azure-functions/functions-how-to-use-azure-function-app-settings?tabs=portal#settings. The System.Environment.GetEnvironmentVariable(name) call returns this value when running in Azure. Locally, the value comes from the local.settings.json file: https://learn.microsoft.com/en-us/azure/azure-functions/functions-dotnet-class-library?tabs=v2%2Ccmd#environment-variables.

BigfootRick
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0

In case of Python runtime, base OS is going to be Linux so you can work it out something like below:

import tempfile

# Get the temporary file
# With suffix/prefix you can add suffix/prefix
# delete=False prevents this file from deletion as soon as you close it
temp_file = tempfile.NamedTemporaryFile(suffix=".tf.json", delete=False)

# File Name with full path
print(temp_file.name)

Source Documentation

kwick
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