How to write an usigned value to file accurately

[WeeBeng]

I would like to find a way to store an unsigned value most accurately so that I could reuse it when I seed my random number generator. Currently, I am writing it to a file. However I realise that what is stored will be dependent on the conversion specifier. Which conversion specifier will ensure the most accurate storage?


unsigned seedtime;

seedtime=(unsigned)time( NULL );// This will be the seed which I //require

appendfile(seedtime);

//code for appendfile

void appendfile( unsigned count)
{
FILE *cfPtr;

if ((cfPtr= fopen("updx.txt","a"))== NULL )
printf ("File could not be opened\n");
else{
fprintf(cfPtr,"%u\n",count);
}


fclose(cfPtr);

}

Currently I am using %u but wonder if there is any other better and more accurate coversion specifier.

Is there any other method to store my unsigned seedtime so that I can use it again when I run my program?

Another question regards my fopen command . Is there any way I can change the directory in which updx.txt can be stored? Currently it is stored in my working directory but I would like to change it to my specification.

Thanx a lot in advance for any help.

[DanM]

1) Save the data to a binary file. Then there is no conversion to be done.

unsigned int nData;

//open the file in binary mode
fwrite(&nData, sizeof(nData), 1, pFile);

2) You can specify the full path like:

fopen("c:\\temp\\updx.txt","a");

Dan

[CBasicNet]

WeeBeng: Why would you want to store your seed in a file?

Just seed the random generator once with the current time will do.

[WeeBeng]

I understand that I only need seed a random number generator once to get a good set of random numbers.
Actually I want to keep seeding the random number generator with the same seed because I want the use the same set of random numbers generated as data to test different sets of functions I have written and compare their results. As the programme will run for a long time for each function, it is preferable that I actually run them at different times using the same data.

Thanks for all the help . Finally managed to get what I want .
Sample working code as follows in case anybody wants to do a similar thing in future.


void appendfile(unsigned number)
{

FILE *cfPtr;

if ((cfPtr= fopen("c:\\updx","wb"))== NULL )
printf ("File could not be opened\n");
else{
fwrite(&number, sizeof(number), 1, cfPtr);

}


fclose(cfPtr);

}

unsigned readfile( char *string)
{

FILE *cfPtr;
unsigned number;

if ((cfPtr= fopen(string,"rb"))== NULL )
printf ("File could not be opened\n");
else{

fread(&number,sizeof(number),1,cfPtr);
}

fclose(cfPtr);

return number;

}