help with writing to file please

This is a discussion on help with writing to file please within the C Programming forums, part of the General Programming Boards category; Hi, I have this code in an if statement inside a mousepressed event and it doesnt appear to be overwriting ...

  1. #1
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    help with writing to file please

    Hi, I have this code in an if statement inside a mousepressed event and it doesnt appear to be overwriting the current file (variables.txt) with the new string

    Code:
    			if (i==2)
    					{
        char my_filename[] = "variables.txt";
    					fopen(my_filename,"w");
    printf(my_filename,"%d\n",2);
    					}
    Any help appreciated,
    thanks,
    Marc

  2. #2
    cwr
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    printf goes to stdout, you can't specify the file. You mean fprintf. By the way, you should check that fopen succeeded.

  3. #3
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    Thanks, how do i check that the file has been opened?

  4. #4
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    p.s changing to fprintf gives a couple of warnings...'parsing argument 1 of printf from incompatible pointer type'

  5. #5
    Registered User Tonto's Avatar
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    You pass the file handle returned by fopen(..) to fprintf. fopen(..) returns a FILE* handle which you should be saving.

  6. #6
    cwr
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    Code:
    {
        char my_filename[] = "foo.txt";
        FILE *myfile;
        myfile = fopen(my_filename, "w");
        if (myfile == NULL)
        {
           /* error message and appropriate action (exit, etc.) */
        }
        fprintf(myfile, "%d\n", 2);
        /* ... */
    }

  7. #7
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    Thanks, I have this now... but I'm not getting any print error output or changed text in the variables.txt file???
    Code:
    				case kEventMouseMoved:
    					kindName = "MouseMoved";
    					GetEventParameter(inEvent, kEventParamMouseLocation, 
    									  typeQDPoint, NULL, sizeof(Point), NULL, &pt);
    					fprintf(stderr, "location - %.0f, %.0f - ", x2, y2);
    					switch (i){
    					case 1:
    					x1=pt.h;
    					y=pt.v;
    					i=2;
    					break;
    					
    					case 2:
    					x2=pt.h;
    					y2=pt.v;
    					i=1;
    					xdouble=x2-x1;
    					ydouble=y2-y;
    					distance=distance+(sqrt(pow(xdouble, 2)))+(sqrt(pow(ydouble, 2)));
    					x1=x2;
    					y=y2;
    					i=2;
    					break;
    					
    					{
        char my_filename[] = "variables.txt";
        FILE *myfile;
        myfile = fopen(my_filename, "w");
        if (myfile == NULL)
        {
    	printf("ouch");
           /* error message and appropriate action (exit, etc.) */
        }
        fprintf(myfile, "%d\n", 2);
        /* ... */
    }
    					}
    					break;

  8. #8
    and the hat of int overfl Salem's Avatar
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    Well you won't by having a break; halfway through your case 2

  9. #9
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    Hmm...this seems to be working (i think) i havent checked the output yet, but this produces an ouch print randomly...them by debugger appears, highlighted at the line:

    0x9000c280 <+0064> lhz r2,12(r16)

    here is my code again:
    Code:
    case kEventClassMouse:
    			className = "Mouse";
    			// get the type or mouse event
    			switch ( GetEventKind( inEvent ) )
    			{
    				case kEventMouseDown:
    					kindName = "MouseDown";
    					clicks=clicks+1;
    					break;
    					
    				case kEventMouseUp:
    					kindName = "MouseUp";
    					break;
    					
    				case kEventMouseMoved:
    					kindName = "MouseMoved";
    					GetEventParameter(inEvent, kEventParamMouseLocation, 
    									  typeQDPoint, NULL, sizeof(Point), NULL, &pt);
    					fprintf(stderr, "location - %.0f, %.0f - ", x2, y2);
    					switch (i){
    					case 1:
    					x1=pt.h;
    					y=pt.v;
    					i=2;
    					break;
    					
    					case 2:
    					x2=pt.h;
    					y2=pt.v;
    					i=1;
    					xdouble=x2-x1;
    					ydouble=y2-y;
    					distance=distance+(sqrt(pow(xdouble, 2)))+(sqrt(pow(ydouble, 2)));
    					x1=x2;
    					y=y2;
    					i=2;
    					
    					
    					{
        char my_filename[] = "variables.txt";
        FILE *myfile;
        myfile = fopen(my_filename, "w");
        if (myfile == NULL)
        {
    	printf("ouch");
           /* error message and appropriate action (exit, etc.) */
        }
        fprintf(myfile, "%d\n", clicks);
        /* ... */
    }
    				break;
    					}
    					break;
    					
    				case kEventMouseDragged:
    					kindName = "MouseDragged";
    					break;
    					
    				case kEventMouseWheelMoved:
    					kindName = "MouseWheel";
    					break;
    					
    				default:
    					break;
    			}
    				break;

  10. #10
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    Scrub that, i think i fixed it by closing the file. I tried opening the file again to read the string it just printed. The output i get is...

    "B-P\306g\232\316}\277\377\363pevent class = Mouse"
    I have no idea what this is lol its certainly not what i want.
    I also opened the file variables.txt and 28 was stored. and sometimes nothing is stored.... :-S

  11. #11
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    Fixed I think...however the text file resides in a folder seperate to where the application is...
    Ah well as long as it works.

    Could anyone please explain how to read two strings instead of the one now please, say for example if they were on different lines in the text file?

    234567 //string1
    101010 //string2

  12. #12
    ATH0 quzah's Avatar
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    Code:
    while happy return values from function reading one line
        if x == 0
            treat the as string 1 when you do something with it
            x = 1
        else
            treat this as string 2 when you do something with it
            x = 0
    There are plenty of methods. Some better than others. All worth experimenting with.


    Quzah.
    Hope is the first step on the road to disappointment.

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