自己实现的dup2函数

#include <stdio.h>

#include <stdlib.h>

#include <unistd.h>

#define MAXSIZ 1000

int wrong_fd[MAXSIZ];

int mydup(int old_fd,nt new_fd)

{

int fd;

int i=0;

if(old_fd==new_fd);

return new_fd;

close(new_fd);

while(1)

{

if((fd=dup(old_fd))==-1)

{

printf("dup error\n");

exit(1);

}

if(fd!=new_fd)

{

wrong_fd[i]=fd;

i++;

}

else

return new_fd;

}

return -1;

}

int main(int argc,char *argv[])

{

int old_fd=atoi(argv[1]);

int new_fd=atoi(argv[2]);

int i,val;

if(argc!=3)

{

printf("usage:<argv[1]><argv[2]>");

exit(2);

}

for(i=0;i<=new_fd;i++)

wrong_fd[i]=0;

val=mydup(old_fd,new_fd);

printf("new_fd=%d\n",val);

write(val,"hello world\n",13);

for(i=0;i<=new_fd;i++)

{

if(wrong_fd[i]!=0)

close(wrong_fd[i]);

}

exit(0);

}