c 删除文件中指定的部分内容

#include <stdio.h>
#include <dirent.h>
#include <string.h>

void search_file(char* dir);
void clear_file(char* FileName,char* Filename1);
 DIR *dp;
    struct dirent *dirp;
    char* file;
    FILE * fp=NULL;
    char n_filename[50];
    char o_filename[50];
 char buf[80];
 int pid;
 int status;
 char* logdir;
    char* logbak;
    char  *optarg;
   
int main(char *argv[]){

 logdir="/usr/local/tmp_file/";
 logbak="/usr/local/tmp_file2/";
 printf("Begin now !");
 
 search_file(logdir);
 

}

void search_file(char* dir){
 if ((dp = opendir(dir)) == NULL)
     {
      printf("directory %s is not found!",logdir);
     }
         /* print err */
    
  while ((dirp = readdir(dp)) != NULL){
      optarg = dirp->d_name;
      /*printf ("%s " , optarg);*/
      
     if ((strstr(optarg,".htm")!=NULL)
       (strstr(optarg,".vbs")!=NULL)
       (strstr(optarg,".asp")!=NULL) ) {

    n_filename[0]='