How do I print a % character into a file
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I am creating an app in App Designer, creating an output file that will be an .m file for another user to run later.
I'd like to put a comment header at the start of this file but I can't double excape the % character
app.SessionFile = fopen(app.SessionFileName,'at');
str = sprintf("%% Parameters: %c%u...",v1,v2...); % Put required string into str - works
str is now "% Paramters: ...." but it won't go out to the file with
fprintf(app.SessionFile,str); % Nothing gets printed, comment gets stripped out!
(0 chars printed)
Also not working
str = sprintf("%%% Parameters:
str = sprintf(" %% Parameters:
Seems like if I have a string I want to put in a text file MatLab shouldn't mess with it.
Also: is 'at' the same as 'wt' ? seems like it always appends anyway with fprint.
3 个评论
Walter Roberson
2024-9-14,21:05
fprintf(MyFile, "%s", "%")
or
fwrite(MyFile, "%s")
Again I caution that neither version of those will add a newline.
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Steven Lord
2024-9-13,18:40
If you don't need str inside your code other than to write it to the file, rather than creating it just write directly to the file.
app.SessionFile = fopen(app.SessionFileName,'at');
fprintf(app.SessionFile,"%% Parameters: %c%u...",v1,v2...);
0 个评论
Walter Roberson
2024-9-13,18:36
Either
fprintf(app.SessionFile,"%s",str);
or
fwrite(app.SessionFile, str);
Note: your str does not appear to include newline. Neither of the above possibilities will insert a newline. The easiest way to include a newline is
fprintf(app.SessionFile,"%s\n",str);
4 个评论
Walter Roberson
2024-9-16,22:07
编辑:Walter Roberson
2024-9-16,22:47
fprintf(MyFile,str) treats str as the format, an interprets it, scanning it looking for % formats.
fprintf(MyFile, "%s", str) treats %s as the format, and treats str as the text to be inserted literally.
There is no special documentation for fprintf(MyFile,str) because it is just treated as an instance of fprintf(fileID,formatSpec,A1,...,An) with str as the formatSpec and with no A1,...,An
If you write an unterminated line to a file and close the file, then the line will be inserted into the file, and the file will just end there; the line can be pulled out of the file normally. It is possible some common DOS utilities might not show the trailing line.
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