CODEWITHSUNDEEP
c++fstreamfile-recovery
rtischer8277
rtischer8277

Reputation: 546

Can an fstream file be made to open if it is already running?

I have a use case where I need to open MyProg.exe after it starts, make some edits and store it again replacing itself. We used to call this self-modifying code which got dubbed as seriously bad coding. However, I do have a real white-hat use case and would like to do just that.

This code fails at open:

std::fstream inOutFile;
inOutFile.open( exePathName, std::ios_base::in | std::ios_base::out | std::ios_base::binary );
if( inOutFile.is_open() )
{ …

As a test to see if it can be done with ordinary commands, I created MyTest.exe program, ran it from a command prompt, and with it running copied MyText.exe from another folder on top of the MyText.exe that was running. No problem, so I know there are some system file commands that will make it work. I was just hoping to use portable ISO c++ idioms where I can. Any thoughts?

EDIT1: I have discovered that Windows now has a comprehensive set of Application Recovery and Restart Functions. I have noticed over the past 2 years that Microsoft has become much better at restarting apps after say power outages. I suspect that it is due to this API's development. Fx, the RegisterApplicationRestart function solves my problem perfectly.

EDIT2: I had to give up trying to use Microsoft's Application and Recovery functions to save command line state. They were too restrictive and only worked for unhandled exceptions and non-responsiveness, and then they required interactive user screens. Fx, they wouldn't work if you had a power outage and just wanted your app to use internal cmdline state info to restart. Looks like I'll have to program my own.

Upvotes: 0

Views: 118

Answers (0)

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