#include <stdio.h>
#include <stdlib.h>
int main(){
FILE *fp;
char ch;
if((fp=fopen("testfile", "a")) == NULL){
fprintf(stderr, "Error opening file.\n",fp);
exit(1);
}
printf("Input a string (Ctrl+D to exit):\n");
while((ch=getchar()) != EOF){
fputc(ch, fp);
}
if(ferror(fp)){
puts("something wrong to read file\n");
}else{
puts("write file success!\n");
}
fclose(fp);
printf("\n");
return 0;
}