How to gain full read/write access to user's AppData folder using a "C" program?

Question

How to gain full read/write access to user's AppData folder using a "C" program?

Thad T 26

Question: I've tried several times to access the user's AppData area programmatically using MSVC 2019 "C" program, but I am unable to gain full read/write access to it. Though it's easy to manually put a file into the area, using a program doesn't seem to work. I am wondering why these areas exist if we can't use them. Can someone provide a solid "C" programming example that demonstrates how to gain access to these areas and place files into them? Also, what steps do I need to follow to have full read/write access into these areas, similar to what other big name programs can do? Could you please provide detailed steps, "C" code snippets, and any relevant documentation to show me how I can full access to the user's appdata areas. Thad.

David Lowndes 2,640 Reputation points MVP

2023-06-18T19:13:29.6966667+00:00

So there's no ambiguity, show us a small example (console program) of what you've tried that hasn't worked for you.
Xiaopo Yang - MSFT 12,731 Reputation points Microsoft External Staff

2023-06-19T01:53:13.3733333+00:00

@Thad T , as @Castorix31 's answer showed CSIDL_APPDATA is designed for the application to use. Could you please show a minimal, reproducible sample without private information?

Thad T 26

Ok, David Lowndes, here's my simple examples of what I'm trying to do; but can't. Thad T. I'll castroix31's suggestion. thx.

 ////   strcpy(thefilename, "C:\\Users\\auror\\appdata\\appfilbin.sys");
   strcpy(thefilename, "C:\\Users\\auror\\appdata\\appfilbin.sys");  
    errI = fopen_s(&OpenRegFile, thefilename, "a+");  
    if (OpenRegFile == NULL) {
        errI = fopen_s(&OpenRegFile, thefilename, "a+");
        if (OpenRegFile != NULL) {
            perror("openned a new file.");
            irv1 = fclose(OpenRegFile);
        }
        else {
            perror("NOPE.");
        }
    }
    else {
        irv1 = fclose(OpenRegFile);
    }

    memset(&thercd, 0, sizeof(thercd));
    memset(&newrcd, 0, sizeof(newrcd));
/// I have to piece together this strcpy, below, line. 
 ////   strcpy(thefilename, "C:\\Users\\auror\\myappuserdatafolder\\appfilbin.sys");
////    recsize = sizeof(struct recordstruct);
    errI = fopen_s(&OpenRegFile, thefilename, "a+");
    if (OpenRegFile == NULL) {
        perror("can't open file.");
    }
    else {
        fseek(OpenRegFile, 0, SEEK_END);  
        long fileSize = ftell(OpenRegFile);
        fseek(OpenRegFile, 0, SEEK_SET);
        totrcds = (int)fileSize / recsize;
//////        fseek(OpenRegFile, 0, SEEK_SET);
        printf("   Number of Records: %2d ... \n", totrcds);
        if(totrcds > 0) errI = 1;
        else {
/// projecteddate  = initialdate plus(+) maxdays;


        }
        switch (errI) {
          case 0:
              thercd.idvalues = 756;
              strcpy(thercd.userXname, myusername);   /// do a sub call to already established functions. 
              thercd.initialdate = 987654321;  //// install date. 
              strcpy(thercd.idstrings, infobuf1);
              thercd.posteddate = 123456789;
              /// thercd.projecteddate = 

              irv = (int)fwrite(&thercd, sizeof(struct recordstruct), 1, OpenRegFile);  /// 0xffff
              printf(" write irv: %d \n", irv);
              irv1 = fclose(OpenRegFile);
              perror("openned/wrote file.");
              break;
          case 1:
              perror("openning read file.");
              fseek(OpenRegFile, 0, SEEK_SET);
              irv = fread(&thercd, sizeof(struct recordstruct), 1, OpenRegFile);
              perror(" reading a file.");
              while (!feof(OpenRegFile)) { // to read file
                 irv1 = fflush(OpenRegFile);
                 printf("> %s,  %d, %s, %d \n", thercd.userXname, thercd.initialdate, thercd.idstrings, thercd.posteddate);
                  printf(">> %d \n",thercd.idvalues);
                  irv = fread(&thercd, sizeof(struct recordstruct), 1, OpenRegFile);
              }
              irv1 = fclose(OpenRegFile);
 ///           find the difference between initialldate and todays date; to if difference is greater than maxdays.
///           if diffence is greater than maxdays and posteddate is an error or no date at all, turn on subscription mode. 
///              else posteddate is a good date, turn off subscription mode, and let the demo know. 


              break;
        }
        osw = 1;
    }

Thad T 26 Reputation points

2023-06-19T04:25:48.13+00:00

Thumbs up to Xiaopo Yang,I'm able to R/W a file within one of three appdata's subdirs.

Thanks for the direction and drive. It works.

1 answer

Your answer

David Lowndes 2,640 Reputation points MVP

2023-06-18T19:13:29.6966667+00:00

So there's no ambiguity, show us a small example (console program) of what you've tried that hasn't worked for you.
Xiaopo Yang - MSFT 12,731 Reputation points Microsoft External Staff

2023-06-19T01:53:13.3733333+00:00

@Thad T , as @Castorix31 's answer showed CSIDL_APPDATA is designed for the application to use. Could you please show a minimal, reproducible sample without private information?
Thad T 26 Reputation points

2023-06-19T04:25:48.13+00:00

Thumbs up to Xiaopo Yang,I'm able to R/W a file within one of three appdata's subdirs.

Thanks for the direction and drive. It works.

Answer 1

Castorix31 90,686

This simple test creates a "Test" folder in my user appdata folder

(C:\Users\Username\AppData\Roaming on my PC (Windows 10 22H2) ) :

					WCHAR wszPath[MAX_PATH] = L"";					
					if (SUCCEEDED(SHGetFolderPath(NULL, CSIDL_APPDATA, NULL, 0, wszPath)))
					{
						PathAppend(wszPath, L"Test");
						if (!PathFileExists(wszPath))
						{
							BOOL bRet = CreateDirectory(wszPath, NULL);
						}
					}

Thad T 26 Reputation points

2023-06-19T04:27:57.18+00:00

Thanks all three people here mentioned, it works. ThadT

Thanks for the direction and drive.
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Anonymous

2023-06-30T07:53:47.3333333+00:00

@Thad T If Castorix31 works for you, please consider accepting his reply as answer. This could help others who are facing the same issue.

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How to gain full read/write access to user's AppData folder using a "C" program?

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