printf - format command of C that will not round of the value

[jerjer]

i have a question
please refer below..

Example:

#include <stdio.h>
int main() {
printf("%6.1f", 123456.123456);
printf("\n%6.2f ", 123456.123456);
printf("\n%6.3f ", 123456.123456);
printf("\n%6.4f ", 123456.123456);
}

output :
123456.1
123456.12
123456.123
123456.1235

at last output the result was 123456.1235 because it was rounded up.

How to display this value by not rounding up?
like 123456.1234 ?

[arnaudk]

Formatted string conversions will always round as far as I know. The only way would be to truncate all decimals beyond the 4th:

#include <math.h>
double truncate(const double val, const int d)
{ 
    double rval = val * pow(10,d);
    rval = (double) floor(rval);
    return rval / pow(10,d);
}
 
int main()
{
    double r =1.23456;
    printf("r = %f, r_4 = %1.4f, r_4t = %1.4f\n",r,r,truncate(r,4));
    return 0;
}
 
// Result: r = 1.23456, r_4 = 1.2346, r_4t = 1.2345