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Exploring FileMaker 18’s File Manipulation Script Steps

One of Filemaker 18’s most exciting new features is the addition of new file manipulation scripts steps. Let’s explore each one and see how to use them!

To test out each script step as you go through this blog post, please download our companion sample file.

Create Data File

FileMaker’s help documentation describes this script step as follows:

“Creates an empty, closed data file, to then open with the Open Data File script step and add data to using the Write to Data File script step.”

This means that this script step works hand-in-hand with several other script steps that I’ll explore further along in this post.

When setting up options for this step, you must specify the file path with the specific file dialog. If you leave the file path blank, it will return error code 100: file is missing. There is another option of “create folders,” which defaults to off. If your file path is missing folders, and you set “create folders” to on, the script step will create the missing folders. If you leave “create folders” to off while missing folders, you will receive an error code of 100: file is missing. If the file already exists, FileMaker will overwrite the original.

What type of files can you create? The help doesn’t specify, so I tested the following:

I was pleasantly surprised to find that they all were created successfully.

Open Data File

Before you can start writing to a file you’ve created (or one that already exists), you must first open the file with the script step “Open Data File”. The file will be considered opened until you close it with the “Close Data File” script step (or quit FMP or close down your computer). If you do not enter a path or you enter an invalid path, you will receive an error code of 100: file is missing.

This script step also asks for a target. The target is where you would like to store the File ID of the data file. You will need this value in order to use some of the other script steps, so don’t forget to set it to something you can reference later (field or variable).

You can also use a new function, Get(OpenDataFileInfo) to find the File IDs if you did not store them in a field or variable. If you try to open a file that’s already been opened, you’ll get an error code of 300: File is in use. There’s a limit of 25 data files that can be opened at the same time, and if you attempt to open more than that, you’ll get an error code of 2: Memory error.

Write to Data File

Now that you know how to create and open a data file, let’s explore writing to one. This script step has four parameters. The data source, which is the data you’d like to write to the data file, can be a field or a variable. In addition, you’ll have to select the character encoding type: UTF-16 or UTF-8.

Which one should you select? According to Wikipedia, “UTF-16 is used internally by systems such as Windows and Java and by JavaScript, and often for plain text and for word-processing data files on Windows. It is rarely used for files on Unix/Linux or macOS. It never gained popularity on the web, where UTF-8 is dominant (and considered “the mandatory encoding for all ” by WHATWG). UTF-16 is used by under 0.01% of web pages themselves. WHATWG recommends that for security reasons browser apps should not use UTF-16.”

This definition gives some hints on the types of files you can write to using this script step, but I tested them all to make sure they all work. I set the data source to the text “Here is some data” and set the encoding to UTF-16, then tried writing that data source to all of the files. Happily, none of the file types gave me an error; all of them worked fine, and I could see that the file size increased after I wrote to each file.

As expected, the only file types that I could actually open and view the data I added was .txt, .html, .java, .json, .csv, and .js. Therefore, you are not prevented from writing to a binary files, but you cannot write to them in any meaningful way. I do not recommend using these script steps to create, read, or write to anything other than text-based files, such as .txt, .html., .java, .json, .cvs, .js, and .log.

I ran the same test with UTF-8 instead of UTF-16 and got the same error-free results; the only difference I noticed is that the file sizes were smaller.

The largest amount of data you can write to a file in a single script step is 64 MB. You can, however, add 64 MB of data multiple times in a row to the same file, appending the data each time.

The last option in this script step is “Append to line feed.” It’s a checkbox which is selected by default. All this does is add a return character before adding the data to the file. You’ll see here the difference from adding data multiple times in a row with the append line feed on versus off.

Read from Data File

The “Read from Data File” script step requires a Target, which is the field or variable that will store the information read from the data file. You must choose if you’d like the data to be read as bytes or UTF-8 or UTF-16; bytes is the default.

File ID is also asked by this script step. If you’d like to limit how much data is inserted into your field or variable, you can set a numerical value in the Amount parameter. If you selected “Read As” as Bytes or UTF-8, then the Amount value’s unit of measure is bytes. If you selected UTF-16, then the Amount value’s is interpreted as the number of Unicode code units to read. When playing with this, I recommend using UTF-16, I found it easier to work with. Leave the amount value blank to read the entire file.

One thing I learned from my testing – if you do enter the amount value to something other than empty, there’s a good chance you’ll need to set the position first (see below about setting positions). When you leave the amount as empty, you’re reading the entire file, so the current position of that file doesn’t matter. This will make more sense after reading about the position script steps.

The read from data file script step cannot read more than 64 MB at a time, so if you need to read more than that, you’ll need to break it up into multiple calls. You can see an example of this in the Help (Example 3).

If the file you are reading is UTF-8 encoded, you should set the “read as” to UTF-8 encoding as well. The same goes for UTF-16 encoding – choose “read as” of UTF-16. When I tried reading a UTF-8 file as UTF-16 encoded, I received back a lot of nonsense (to me!) characters.

Below is a summary of what happens when you mix and match encoding methods when reading and writing to data files.

If the file you are reading is binary (which is basically anything that’s not a text-based file) then you should set the “read as” as bytes. In most cases, using the Read From Data File script steps for binary files is very similar to Insert File script step, because you’ll be saving the binary data into a container field. One key difference, however, is that Read From Data File is compatible on the server – but only in server compatible locations, which are the documents folder and the temporary folder.

Close Data File

The Close Data File script step is pretty straightforward. It only takes one parameter: the File ID. Closing a file makes it unavailable for reading and writing to the open data file and allows you to complete script steps that require the data file to be closed, like delete the file.

If you’d like to close all open files in one script step, simply assign the parameter to an asterisk with double quotation marks surrounding it (“*”). In addition, quitting FMP will also close all opened data files. If you attempt to close a file that’s not open, you will receive the error code: 100 File is Missing.

At this point, you might think I’ve covered all the basics, but there’s still more! Let’s take a look at what else we can do besides open, read, write and close data files.

Get Data File Position

This script step will not return the “physical” position of the data file on your monitor, which is what I initially expected. Instead, it returns the read-write position inside of the data file – which is the number of bytes from the start of the file text where the file reading or writing data will start. When a file is first created, the read-write position is defaulted to 0. At the end of the data file, the position is the same as the size of the file.

This script step takes in 2 parameters, File ID and Target; the target is where you would like to store the results of the read-write position.

Set Data File Position

This script step takes two parameters, the file ID and the new position to which you’d like to set the file. The new position is the number of bytes from the beginning of the file. When you read or write to a file, it will start at this position. If there is data after this position when writing to a file, it will get overwritten. For example, if my file says “123456789” and I reset the data position to 0 and then write to the file “hello,” the data file will now say “hello56789.”

Get File Size

This script step will tell you the size of any file in bytes. It takes two parameters: the path to the file, and the field or variable to which you’d like to store the file size. You can use this script step in conjunction with the Set position script steps above if you’d like to set the position to the end of the file.

Delete File

This script step just takes 1 parameter: the path to the file. And the file must be closed in order to be deleted. If you attempt to delete an open file, you will receive an error 300: File is locked or in use. Note that this script step and the one before it both reference “File” instead of “Data File.” That’s because you can use them to the size and to delete any type of file, not necessarily just a data file.

Get File Exists

This script asks for the path to the file whose existence you’d like to check, and also for field or variable that stores the result ( 1 = true, file exists, and 0 = false, file does not exist). I recommend including this step before using any other of the file script steps that require a path, such as Delete File, Get File Size, Create Data File, Open Data File and Rename File.

Rename File

This file is asking for the path to the existing file and the new name for the file in the path provided.

Try It Out Yourself

I have created a demo file where you can play with all of these new script steps and get a better understanding on how they work together. This file keeps track of all the files you create, open, close, and delete in the Data Files portal.

Get the demo file

You’ll also notice a switch for turning the Error Logging on and off. This is another new script step that will automatically log any script errors into a file and save it in the “ScriptErrors.log” file, which is created in your documents folder when you log your first error. You can even add your own expression to be evaluated whenever a script error is logged.

Another object you’ll notice is a button for refreshing the portal. This button uses the new FileMaker Pro 18 function Get ( OpenDataFileInfo). The script attached to this button takes all the open data files and adds them to the list if they aren’t already there.


At this point, you may be thinking “Hmm… I still have some questions…” Well, I did too! Here are some of my questions along with the answers I came up with. If you have any other questions, please add them to the comments below.

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