ubuntu8.04如何修改默认文件关联打开程序

#include <pthread.h>
int pthread_create(pthread_t *thread,pthread_attr_t *attr,
void *(*start_routine)(void *),void *arg);
void pthread_exit(void *retval);
int pthread_join(pthread *thread,void **thread_return);

#include <stdio.h>
    #include <unistd.h>
    #include <stdlib.h>
    #include <string.h>
    #include <errno.h>
    #include <pthread.h>
    #include <dirent.h>
    #include <fcntl.h>
    #include <sys/types.h>
    #include <sys/stat.h>
    #include <sys/time.h>

    #define BUFFER 512
    struct copy_file {
    int infile;
    int outfile;
    };
    void *copy(void *arg)
    {
    int infile,outfile;
    int bytes_read,bytes_write,*bytes_copy_p;
    char buffer[BUFFER],*buffer_p;
    struct copy_file *file=(struct copy_file *)arg;
    infile=file->infile;
    outfile=file->outfile;
    /* 因为线程退出时,所有的变量空间都要被释放,所以我们只好自己分配内存了 */
    if((bytes_copy_p=(int *)malloc(sizeof(int)))==NULL) pthread_exit(NULL);
    bytes_read=bytes_write=0;
    *bytes_copy_p=0;
    while((bytes_read=read(infile,buffer,BUFFER))!=0)
    {
    if((bytes_read==-1)&&(errno!=EINTR))break;
    else if(bytes_read>0)
    {
    buffer_p=buffer;
    while((bytes_write=write(outfile,buffer_p,bytes_read))!=0)
    {
    if((bytes_write==-1)&&(errno!=EINTR))break;
    else if(bytes_write==bytes_read)break;
    else if(bytes_write>0)
    {
    buffer_p+=bytes_write;
    bytes_read-=bytes_write;
    }
    }
    if(bytes_write==-1)break;
    *bytes_copy_p+=bytes_read;
    }
    }
    close(infile);
    close(outfile);
    pthread_exit(bytes_copy_p);
    }
    int main(int argc,char **argv)
    {
    pthread_t *thread;
    struct copy_file *file;
    int byte_copy,*byte_copy_p,num,i,j;
    char filename[BUFFER];
    struct dirent **namelist;
    struct stat filestat;
    /* 得到当前路径下面所有的文件(包含目录)的个数 */
    if((num=scandir(".",&namelist,0,alphasort))<0)
    {
    fprintf(stderr,"Get File Num Error:%s\n\a",strerror(errno));
    exit(1);
    }
    /* 给线程分配空间,其实没有必要这么多的 */
    if(((thread=(pthread_t *)malloc(sizeof(pthread_t)*num))==NULL)||
    ((file=(struct copy_file *)malloc(sizeof(struct copy_file)*num))==NULL)
    )
    {
    fprintf(stderr,"Out Of Memory!\n\a");
    exit(1);
    }

    for(i=0,j=0;i<num;i++)
    {
    memset(filename,'\0',BUFFER);
    strcpy(filename,namelist[i]->d_name);
    if(stat(filename,&filestat)==-1)
    {
    fprintf(stderr,"Get File Information:%s\n\a",strerror(errno));
    exit(1);
    }
    /* 我们忽略目录 */
    if(!S_ISREG(filestat.st_mode))continue;
    if((file[j].infile=open(filename,O_RDONLY))<0)
    {
    fprintf(stderr,"Open %s Error:%s\n\a",filename,strerror(errno));
    continue;
    }
    strcat(filename,".bak");
    if((file[j].outfile=open(filename,O_WRONLY|O_CREAT,S_IRUSR|S_IWUSR))
    <0)
    {
    fprintf(stderr,"Creat %s Error:%s\n\a",filename,strerror(errno
    ));
    continue;
    }
    /* 创建线程,进行文件拷贝 */
    if(pthread_create(&thread[j],NULL,copy,(void *)&file[j])!=0)
    fprintf(stderr,"Create Thread[%d] Error:%s\n\a",i,strerror(errno));
    j++;
    }
    byte_copy=0;
    for(i=0;i<j;i++)
    {
    /* 等待线程结束 */
    if(pthread_join(thread[i],(void **)&byte_copy_p)!=0)
    fprintf(stderr,"Thread[%d] Join Error:%s\n\a",
    i,strerror(errno));
    else
    {
    if(bytes_copy_p==NULL)continue;
    printf("Thread[%d] Copy %d bytes\n\a",i,*byte_copy_p);
    byte_copy+=*byte_copy_p;
    /* 释放我们在copy函数里面创建的内存 */
    free(byte_copy_p);
    }
    }
    printf("Total Copy Bytes %d\n\a",byte_copy);
    free(thread);
    free(file);
    exit(0);
    }