Thread: Problem creating file in C -- possible permission error?

My code system includes an extensive library file written by someone else, which contains a number of function definitions etc. In the past, I've never had problems calling on this code. However, I have recently had to change PCs, and the new PC that I'm working on (which has Windows 7, compared to my previous PC that had XP) is resulting in errors that had never been present when using the identical code on my earlier PC.

Specifically, the straightforward code is

Code:

strcpy(filename, fileprefix);
strcat(filename, "outfile.out");
      
if ((refmap = fopen(filename,"w")) == NULL) {	   
      fprintf(logfile,"Could not create outfile.out file.\n");
      strcpy(error_msg,"Could not create outfile.out file.");
      fclose(logfile);
      return 1;
}

There should be nothing wrong with the above code. However, when I try to run my system, I invariably get the error message, "Could not create outfile.out".
I'm thinking that this may be a permissions issue.

When I right-click on my working folder, it shows that the folder & its subfolders are read-only. When I uncheck that box so that these *aren't* read-only and click Apply, the process seems to complete successfully, but then if I check this folder's properties again, it's back to being read-only.

My apologies that this isn't strictly a C programming question, but has anyone encountered such a problem? I've been told that it doesn't matter if this read-only box is checked, because I can still work with my files; however, this is the only explanation I have for why I wouldn't be able to create the outfile.out file. Any ideas about how to get my files to not be read-only? When I try to adjust the properties, I *am* already working in my Administrator account...

Any suggestions are welcome. Thanks in advance.

Calling strerror() or perror() would at least tell you something about WHY you couldn't write to the file.

Also, print out the actual full path. Certainly past Vista, trying to write outside your own "c:\users\me" area is going to come with strings attached.

Thanks for your responses. Some updates:

-- When I switch modes and enter Administrator mode, it's unfortunately still the same outcome as before: even after I apply my changes to remove the read-only property from my folder, and it appears to complete successfully, checking the folder's properties reveals that it's *still* read-only...

-- I'm finding that I'm no longer able to compile my code (I now get a 'cannot open file: permission denied' error where I had once been able to compile with no errors)... maybe switching to the Administrator mode changed something? I would *think* that switching to Adminstrator would give me *more* capabilities, not fewer...

I wonder if some/all of these problems are Windows 7-specific.

Yes this is a permissions error of sorts...

Windows 7 is totally non-receptive to data files being created in the "C:\program files" heirarchy. You will trigger the UAC and all kinds of permission errors doing that.

The simple solution is to move your code into your user folders... Click your name on the start menu, this will open your home folder... simply make a folder "Programming" or such and move all your code to it, leaving the compilers in the program files folders.

Second, you will find that a lot of code will trigger the UAC unless you include a manifest in your program's resources...

Code:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
  <assemblyIdentity type="win32"
                    name="AutoLogon"
                    version="1.0.0.0"
                    processorArchitecture="X86" />
  <description>
    Auto logon tool
  </description>
  <dependency>
    <dependentAssembly>
      <assemblyIdentity type="win32"
                        name="Microsoft.Windows.Common-Controls"
                        version="6.0.0.0"
                        processorArchitecture="X86"
                        publicKeyToken="6595b64144ccf1df"
                        language="*" />
    </dependentAssembly>
  </dependency>
  <trustInfo xmlns="urn:schemas-microsoft-com:asm.v3">
    <security>
      <requestedPrivileges>
        <requestedExecutionLevel  level="asInvoker" 
                                  uiAccess="false" /> 
      </requestedPrivileges>
    </security>
  </trustInfo>
</assembly>

Be very careful about editing this... change only the program name and description. Change nothing else.

Also Win7 gets real snarky about trying to create data files in the program folder under "program files". It will redirect them to a per-user data folder which is exposed by the %appdata% environment variable. The result of this "virtualization" is that when your programs go to open files, they will fail, since the files aren't where it thought it saved them. The new right way is to create folders under the user's home folder or in "documents" for your data files...

Finally, locate your ide, compiler and linker in the "program fiiles" heirarchy and right click on them... select Properties then Compatibility and check the "Run As Administrator" box on each.

Yeah, I know... "And exactly what the $#%&#& were they thinking???"


Hopefully this will fix your problem.

Thanks for your detailed help, CommonTater. I am seriously considering switching back to XP; all of the debugging steps you mentioned just don't seem like they'll be worth the effort -- i.e., these debugging steps may allow my code to work for now, but how can I predict which additional errors or incompatibilities Windows 7 will cause as I continue developing my code? I am using Matlab R2007b & several related pieces of Mathworks software; mex-files; dlls; C code; a C-mex s-function;... I would not look forward to continual debugging as Windows 7 finds new nuances of my developing system to be incompatible with. Is this a legitimate concern that I have?

Would you agree with my inclination to switch back to XP? Can you foresee any downsides to doing so? Thanks a lot for your input.