![\"Hey,](\"https:\/\/devblogs.microsoft.com\/wp-content\/uploads\/sites\/29\/2019\/02\/q-for-powertip.jpg\" "\\"Hey,")
<\/h2>\n <\/h2>\nHey, Scripting Guy! How can I create a file name from the date? I have this application that creates a log file, and every hour I would like to save that log file as a file whose name is generated from the current time stamp. Can this be done?<\/p>\n
– RH<\/p>\n
![\"Spacer\"](\"https:\/\/devblogs.microsoft.com\/scripting\/wp-content\/uploads\/sites\/29\/2019\/05\/spacer.gif\")
![\"Hey,](\"https:\/\/devblogs.microsoft.com\/wp-content\/uploads\/sites\/29\/2019\/02\/a-for-powertip.jpg\" "\\"Hey,")
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Hi RH,<\/p>\n
Ever since I read your e-mail message, I have had this old Rolling Stones tune<\/a> stuck in my head (which is much better than having “I’ve got a brand new pair of roller skates\u2026”), and it is causing some serious brain itch<\/a>. So I was back in Munich, Germany, a couple of years ago, and the Stones were on stage. It was a fine spring evening, ink-black sky, full moon, and not a cloud in the sky. The lights went off and two flame pots erupted. The crowd went wild and\u2026sorry.<\/p>\n The main logic of today\u2019s script is contained in a function we have called GetFileName<\/b>. Inside this function we use a couple of pretty cool methods to create the file name for you. Here\u2019s the sscript:<\/p>\n The first thing we do is create a function named GetFileName<\/b>. To do this we use the function<\/b> keyword, and give it the name of the function. We are going to pass a variable to the function by reference. VBScript functions are talked about here<\/a>. When we pass a variable to a function by reference, it means we will be changing the value of the variable inside the function, and then handing that value back to the code that called the function. <\/p>\n Another way to call a function is to pass a variable by value. When that happens, the value of the variable is what is important. Inside the function the value of the variable may change, but when the script is done, the value of the variable remains unchanged. This is seen here in this demo script:<\/p>\n Back to the GetFileName<\/b> function\u2014when you want to pass a variable by reference, you need to use the [ref]<\/b> type constraint to make the variable into a reference type. This is seen here. <\/p>\n Next we need to get a list of all the things you are not allowed to have in a file name. Dude! You mean you cannot remember all the things you are not allowed to have in a file name? (Uh, join the club.) I know some of the things, and I know some things that I do not like in file names (such as spaces), but that is about it. I generally stick with letters and numbers for my file names. But suppose you needed to know exactly what you could not have in a file name; how would you do that? Well it is easy. You can use the GetInvalidFileNameChars<\/b> method from the System.Io.Path<\/b> .NET Framework class. If you would like to see a list, copy this code into the Windows PowerShell command window, as seen here:<\/p>\n <\/p>\nFunction GetFileName([ref]$fileName)\n{\n $invalidChars = [io.path]::GetInvalidFileNamechars() \n $date = Get-Date -format s\n $fileName.value = ($date.ToString() -replace \"[$invalidChars]\",\"-\") + \".txt\"\n}\n\n$fileName = $null\nGetFileName([ref]$fileName)\nnew-item -path c:\\fso -name $filename -itemtype file\n<\/pre>\nFunction addOne($in)\n{\n $in = $in + 1\n 'In the function $in equals ' + $in \n}\n$in = 1\naddOne($in)\n'Out of the function $in equals ' + $in\n<\/pre>\nFunction GetFileName([ref]$fileName)<\/pre>\n
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