Fopen returning "Unable to find file. Ensure file exists and path is valid"

I am trying to print a file with the data and time it was written.

currentime = now; %gets current time in numeric value

currentdate = datestr(datetime(currentime,'ConvertFrom','datenum')); %converst time to day/month/year format

printfile = "Milestone_5_results_date.txt";

printfile = strrep(printfile,'date',currentdate);

fileID = fopen(printfile, 'a');

If I get rid of the last printfile line the code outputs to Milestone_5_results_date.txt just fine, but when I try to add the data in place of the string it breaks the code? I am very confused on how the name of the file makes it not be able to be open.

Answer 1

[Star Strider]

I am not certain what the problem is.

Try this —

currentdate = string(datetime('now', 'Format','dd/MM/yyyy')); %converst time to day/month/year format
printfile = "Milestone_5_results_"+currentdate+".txt"

printfile = "Milestone_5_results_28/04/2022.txt"

Make appropriate changes to get the desired format for ‘printfile’.

.

[Caleb Walker]

This fixed the error where fopen wasnt working, however now when I go to print a line to the file it says there is an invalid file type.

Code:

currentdate = string(datetime('now', 'Format','dd/MM/yyyy')); %converst time to day/month/year format

printfile = "Milestone_5_"+currentdate+".txt";

fileID = fopen(printfile, 'a'); %opens a file with the given name and allows data to be written to it

fprintf(fileID,"Dataset Name \t Maximum Freq (Hz) \t Amplitude Location \tVoltage RMS \tTolerance \t Signal Score \t Pass/Fail\n");

fclose(fileID);

Error: Error using fprintf

Invalid file identifier. Use fopen to generate a valid file identifier.

Im still unsure what the issue might be, when I run it without the added string it works just fine, but the moment I add the currentdate part it causes an issue, maybe I am just missing something.

[Star Strider]

The problem may be ‘currentdate’ because of the format. Most operationg systems consider forward- and back-slant characters as reserved because they separate elements of path structures.

Try this instead:

currentdate = string(datetime('now', 'Format','dd-MM-yyyy'))

It would be easier to create a table with the data and the variable names, then use the writetable function. That will make everything easier.

[Caleb Walker]

That was 100% the problem, I am very stupid. Thank you tons for the help.

[Star Strider]

As always, my pleasure!

Not stupid at all! That’s how we learn. (I didn’t originally see it as a problem and only thought of that possibility later.)