c中的fscanf无法读取双值

“%f”

格式在和之间的行为不同

---

对于

scanf

（和系列）

，%f

读入

浮点

变量，而不是

双精度

。如果你想读一个

double

，那么你需要

scanf

的

%lf

格式，尽管它们属于同一个家族，OP询问的是

fscanf（）

，而不是

scanf（）

# include <stdio.h>
# include <io.h>
# include <stdlib.h>
int main(int argc,char *argv[]){
   FILE *tfptr;
    int accno;
    double balance;
    if((tfptr=fopen("trans.dat","w"))==NULL){ //check the file trans.dat existed or not
        printf("cannot open file. \n");
        exit(1);
    }
    fscanf(stdin,"%d%f",&accno,&balance);/* read from keyboard */
    fprintf(tfptr,"%d %f",accno,balance);/* write to file */
    fclose(tfptr); //close the file trans.dat
    if((tfptr=fopen("trans.dat","r"))==NULL){ //check the file trans.dat file existed or not
        printf("cannot open file. \n");
        exit(1);
    }
    fscanf(tfptr,"%d%f",&accno,&balance);/* read from file  */
    fprintf(stdout,"%d %f",accno,balance);/* write to screen */
    return 0;
}

12  2.3
12   0.000000
--------------------------------
Process exited with return value 0
Press any key to continue . . .