Error Saving Fig with complicated filename

Hello, is there a reason why a matlab figure won't save when the filepath is like this:

completepath =
    'F:\IMAGES\2026\Mar\05\08_TestData-2100\05-Mar-2026_08:57:24_Starting_ZTT_-2100.fig'
     saveas(F1,completepath);     % call save as function to save the file   

I get this:

Error using save
Unable to open file "F:\IMAGES\2026\Mar\05\08_TestData-2100\05-Mar-2026_08:57:24_Starting_ZTT_-2100.fig" for output.
Error in matlab.graphics.internal.figfile.FigFile/write (line 33)
save(obj.Path, obj.MatVersion, '-struct', 'SaveVars');
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Error in savefig (line 33)
FF.write();
^^^^^^^^^^

Answer 1

[Stephen23]

"is there a reason why a matlab figure won't save when the filepath is like this"

Yes, because colons are not valid in MS Windows filenames:

'F:\IMAGES\2026\Mar\05\08_TestData-2100\05-Mar-2026_08:57:24_Starting_ZTT_-2100.fig'
                                                      ^  ^

In Windows path syntax, the colon is reserved for:

1. Drive letter specification e.g. "F:\..."
2. Alternate Data Streams (ADS) syntax : "filename:streamname"

Allowing : in normal filenames would conflict with this parsing. Windows prohibits the following characters:

< > : " / \ | ? *

So the two colons in "08:57:24" make the filename invalid.

Read more: https://learn.microsoft.com/en-us/windows/win32/fileio/naming-a-file

[Jason]

thanks for pointing that out!

[Steven Lord]

FYI if you're using datetime to generate the date-and-time part of those filenames, you can change the datetime's Format property to avoid the colons.

d = datetime('now')

d = datetime
   05-Mar-2026 15:05:54

formatWithColon = d.Format

formatWithColon = 'dd-MMM-uuuu HH:mm:ss'

d.Format = replace(d.Format, ':', '_')

d = datetime
   05-Mar-2026 15_05_54

formatWithoutColon = d.Format

formatWithoutColon = 'dd-MMM-uuuu HH_mm_ss'

Or you might want to convert the datetime to a string then do the processing on that string.

d2 = datetime('now')

d2 = datetime
   05-Mar-2026 15:05:54

s = string(d2)

s = "05-Mar-2026 15:05:54"

s = replace(s, ":", "_")

s = "05-Mar-2026 15_05_54"

[Jason]

Thanks