im trying to right align data that i have written to file with fprintf, but im not sure how i would do so in C. ive looked around and there are many solutions for C++ and C# but havent found one for to right align in regular C.

Be more specific. Formatted text with fprintf is right aligned by default, so clearly you want to do something other than that.

well basically im writing to file with this

while(fgets(prime, 2000, fin)!=NULL) { 
    		root_value = atof(prime);
			
			fprintf(fout, "%.0f\t", root_value);
                     }

now i get the output that im looking for, however, it comes out like this
1
3
4
11
64
128
882

instead of this
                    1
                    3
                    4
                   11
                   64
                  128
                  882

Add a field width:

fprintf(fout, "%21.0f\t", root_value);