How can we permanently delete the file using Microsoft flow?

Question

Using delete file action the file is deleted but goes to recycle bin.

Answer 1

You can delete the file(s) permanently using REST API "HTTP DELETE".

$.ajax({  
        url: _spPageContextInfo.webAbsoluteUrl + "/_api/web/getfilebyserverrelativeurl('/Shared%20Documents')",  
        type: "POST",  
        contentType: "application/json;odata=verbose",  
        headers: {  
            "Accept": "application/json;odata=verbose",  
            "X-RequestDigest": $("#__REQUESTDIGEST").val(),  
            "IF-MATCH": "*",  
            "X-HTTP-Method": "DELETE",  
        },  
        success: function(data) {  
            alert("success");  
        },  
        error: function(data) {  
            alert("failed");  
        }  
    });  

You can send the items to the Recycle Bin by adding "/recycle()" to the API URL.

A successful Delete returns no data. A successful recycle() returns the GUID for the recycled item.

Reference

Answer 2

As Sohail's reply, if you want to permanently delete the file using Microsoft flow, we need call rest api below to achieve it.

url: https://site url/_api/web/GetFileByServerRelativeUrl('/Folder Name/file name')
method: POST
headers:
    Authorization: "Bearer " + accessToken
     X-RequestDigest: form digest value
    IF-MATCH: etag or "*"
    X-HTTP-Method:"DELETE"

Here is an example about how to delete all Subsites using REST API in Flow for your reference.

Microsoft Flow | SharePoint Online | Delete all Subsites using REST API

More information:

HOW TO CALL SHAREPOINT REST WEBSERVICE FROM MICROSOFT FLOW