If you’re going to download multiple files, you likely already have a list of URLs. For example, you can timestamp the folder name when you run the program so you can go back through the folders later and know when you ran the macro. This approach is particularly useful if you frequently automate repetitive tasks. You can make the folder using VBA before calling the URLDownloadToFile function. If the download folder doesn’t exist, don’t worry. You won’t get any error messages, but your file won’t be downloaded anywhere. If a folder with the path you specify doesn’t exist, your download will fail. Because we do that, it’s important to have a trailing backslash at the end of your download path. Notice how we concatenated our download path ( dlpath) and our file name. If you have a folder named C:\DownloadedPics\, there will now be a file entitled HK Skyline.jpg in that folder. Private Declare PtrSafe Function URLDownloadToFile Lib "urlmon" _ Alias "URLDownloadToFileA" ( ByVal pCaller As Long, ByVal szURL As String, _ ByVal szFileName As String, ByVal dwReserved As Long, ByVal lpfnCB As Long ) As Long Sub download_HK_picture () imgsrc = "" dlpath = "C:\DownloadedPics\" URLDownloadToFile 0, imgsrc, dlpath & "HK Skyline.jpg", 0, 0 End Sub You should have the following image path on your clipboard: We can access its URL by right-clicking and then clicking “Copy Image Location” or “Copy Image Address.” The words may change depending on your browser, but you get the idea.Ĭopy the URL of the image by clicking the "Copy Image Location" option. Under the architecture section on the Hong Kong Wikipedia page, there is a nice panorama of Hong Kong at night. You do not want to pass the URL of the webpage where the picture is embedded. In the HTML, every picture on every webpage is represented as a link to the picture’s very own URL, and that’s the URL we need to pass to the URLDownloadToFile function. This tutorial focuses on downloading images, but the function is just as useful for downloading other file types.Īnyway, we’re going to start with just one picture: a cityscape picture from Hong Kong’s Wikipedia page as of November 2018. Admittedly, using VBA would be inane for a single picture, but if you have hundreds of pictures to download, this task would be a perfect automation target. You could right-click then “Save Image as…”, or you could use VBA. Let’s say you find a picture you like and you want to download it. The other arguments can almost always be set to 0. These arguments represent the URL source and the name of the file after we’ve downloaded it. We’ll get to that soon, but for now, the most important parts are the szURL and szFileName parameters. This makes checking whether the download started much easier. We can see the return type is Long, which means the function will return a whole number. All we have to do is throw this declaration at the top to begin using it. All the code needed to access a URL, download the stream of bits and bytes, then structure them back into a file on the hard drive is conveniently wrapped into this single function. Libraries are basically sets of prewritten code, usually optimized by the library developer (Microsoft, for this library). I know this is a rather long function declaration. We can do that by placing this line of code at the top of a VBA module: Before we can use it, we need to declare the function and connect to it from VBA. The URLDownloadToFile function is part of the Windows library urlmon. In this tutorial, we’re going to download files using a Windows function called URLDownloadToFile. This is probably the most common way to download files, but we’re not going to do it this way. There are a number ways to download files using VBA, including using an XMLHTTP request to stream the binary data or text associated with your file, and then using the SaveToFile method to finish saving the downloaded file. Once you finish the tutorial, you’ll be able to easily download URL files yourself. This guide lays out the practical requirements for downloading files from the internet using VBA. Where it makes sense to explain, we’ll explain, but there are times when we’ll simply gloss over the technical parts and just use the code without much explanation. It contains multiple steps and pieces of code that are outside the general scope of a “downloading files with VBA” tutorial. This tutorial is a little more involved than our recent tutorials. This is automation of a rather dull task, so implementing it hopefully has a positive impact on your work. We might already know these URLs, or we may have to scrape them from the web and parse them. In this tutorial, we will learn how to use VBA to programmatically download files based on URLs. It will also make human jobs less boring (assuming we still have jobs). Automation can thrash labor markets while simultaneously exploding productivity and profits.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |