这是我正在使用C语言编写的程序的基本代码.我试图检测输出文件是否已经存在,如果它确实存在,我想询问用户是否要覆盖它.这就是我首先使用fopen(outfilename,"r")打开outfilename文件的原因; 而不是fopen(outfilename,"w");.
它检测文件不存在的情况,但是,如果它确实存在则执行printf("输出文件已存在,覆盖(y/n):"); 声明但完全忽略了scanf("%c",&yn); 声明!
如果文件不存在,程序末尾的printf读取"yn = 0",如果存在,则读取"yn =".有谁能够帮我？
#include <stdio.h>
#include <stdlib.h>
#include <float.h>
#include <string.h>
int main(void) {
FILE *inf;
FILE *outf;
char filename[21],outfilename[21];
char yn='0';
printf("Please enter an input filename: ");
scanf("%s",&filename);
printf("Please enter an output filename: ");
scanf("%s",&outfilename);
/* Open file for reading */
inf=fopen (filename,"r");
outf=fopen(outfilename,"r");
/*check that input file exists*/
if (inf!=NULL) {
/*check that the output file doesn't already exist*/
if (outf==NULL){
fclose(outf);
/*if it doesn't already exist create file by opening in …