1、

#include <stdio.h>

int main(void)
{
    FILE *fp;
    
    char filename[128];
    printf("filename: "); scanf("%s", filename);
    
    fp = fopen(filename, "r");
    
    if(fp != NULL)
    {
        fp = fopen(filename, "w");
        printf("%s clear successfully!", filename);
        fclose(fp);
    }
    else
    {
        printf("%s does not exist\a.\n", filename);
    }
    
    return 0;
    
        
}