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How to fprintf directory name?

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Alon Rozen
Alon Rozen on 6 Dec 2018
Commented: Alon Rozen on 6 Dec 2018
Hi all,
I am geting a directory name using:
Dir_Name = uigetdir;
Into Dir_Name, which is of type 'char', I get something like D:\Data\My_Projects\Project_1.
I am trying to print this Dir_Name into a text file using:
Log_File = fopen('My_Log_File.txt','w');
I get a warning which says: Escaped character '\D' is not valid. See 'doc sprintf' for supported special characters.
I read that document very carefuly but apparently missing the hint what to do. Is the first D the problem? The second?
If I can't print the full directory into the log file, the last directory name, in this case 'Project_1' is also a good solution for me.
Is there a way to pring the full directory? Is there a way to extract the last directory name?


madhan ravi
madhan ravi on 6 Dec 2018
why not just use sprintf()? as shown in the message they are quite handy
Alon Rozen
Alon Rozen on 6 Dec 2018
I don't understand how. The message hint that I should use it but I coudn't figure out how to get it printed.

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Accepted Answer

Robert U
Robert U on 6 Dec 2018
Hi Alon Rozen,
There are some syntax issues in your example:
Dir_Name = uigetdir;
Log_File = fopen('My_Log_File.txt','a');
If you use 'w' as permission of fopen() new entries would overwrite old ones. Since uigetdir() does not provide multiple lines the '\n' seems to not make sense there. If you want to append new entries to file use 'a' instead.
Kind regards,


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Alon Rozen
Alon Rozen on 6 Dec 2018
Hi Robert,
I tried adding %s to the fprintf command but I get the same warning and it only prints:
I think that the directory seperator sign '\' is the cause of the problem. But a full path might contain several of these separators. And beforehand I don't know where thay are.
Thanks again,
Jan on 6 Dec 2018
@Alon: The suggested code does work definitely:
fprintf(Log_File, '%s\n', Dir_Name);
Please try it exactly as written. The problem is, that '\' is the "escape character" in the format string. If you want to display it in a format string, you need to use two of them: '\\'. To display a path, do not include the folder name in the format string, but in the string to be displayed. See this:
folder = 'C:\Temp\'
fprintf(folder) % Stops because \T is not a valid control sequence
fprintf(strrep(folder, '\', '\\')) % Works because \ got \\
fprintf('%s\n', folder) % Best solution
Without specifying the file id as first input, fprintf writes to the command window, which is easier for controlling the output. Please read the documentation of fprintf again to understand the difference between the format string and the data to be written.
"tried adding %s to the fprintf command" - Obviously there is a mistake in this trial, so prefer to post the code instead of describing it by words.
Alon Rozen
Alon Rozen on 6 Dec 2018
Thanks Jan and Robert,
Unlike what I wrote above - I repeted exacly what Robert suggested (carfully this time) and it works! Thanks :)
When I tried to include the strrep function it added another '\' wherever there was one. Apparently the command %s takes care of this.
Thanks again,

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