c++ - Why isn't anything being written to my file? -

i'm making program opencv , want record x,y coordinates of 2 objects i'm tracking. i've retrieved data fine , using display coordinates on-screen, i've been struggling write log file.

i have function pass relevant data to, , sure program reaching function because file being created.

can please tell me why "test.txt" empty? thank in advance.

here code:

void savedata(int leftx, int lefty, int rightx, int righty, int distance){     logfile.open("test.txt");      //timer     time_t start = time(0); //set initial time point      //counter     int counter = 0;      //string coordinates     //string coordinates string coords = "left x: " + inttostring(leftx) + "  lefty: " + inttostring(lefty) +     "  right x: " + inttostring(rightx) + "  right y: " + inttostring(righty) + "  distance between: " + inttostring(distance) + "\n";      //if 1 minute has passed     if (start - time(0) == 60){          //write coordinates log file         logfile << coords;          //increment counter         counter++;          //after 30 mins of recording exit program         if (counter == 30){             //close log file             logfile.close();              //exit no errors             exit(0);         }          //reset time 0         start = time(0);     } } 

in c , c++ variables created in stack (aka non pointer variables) confined scope. suppose function called inside external loop. counter not seen loop. same start.

moreover there logical issues in code:

1. start-time(0)==60 tested once. time(0) greater start.
2. counter increment 1 (and won't since start-time(0)<0) since isn't inside loop, in if clause.

i can suggest pseudocode based on i've intended wanna code posted there:

void savedata(data){     open file      setup start=time(0) , counter=0      format output string      while(counter<=30){         if((int)(time(0)-start)%60==0){ //seconds_passed=60*n, n integer             write data             counter++         }         }      close file } 

have fun

gf

edit: if call function external infinite loop have pass counter reference (so increments inside function seen outside) , start argument.