github.com/afumu/libc@v0.0.6/musl/src/unistd/dup2.c (about)

     1  #include <unistd.h>
     2  #include <errno.h>
     3  #include <fcntl.h>
     4  #include "syscall.h"
     5  
     6  int dup2(int old, int new)
     7  {
     8  	int r;
     9  #ifdef SYS_dup2
    10  	while ((r=__syscall(SYS_dup2, old, new))==-EBUSY);
    11  #else
    12  	if (old==new) {
    13  		r = __syscall(SYS_fcntl, old, F_GETFD);
    14  		if (r >= 0) return old;
    15  	} else {
    16  		while ((r=__syscall(SYS_dup3, old, new, 0))==-EBUSY);
    17  	}
    18  #endif
    19  	return __syscall_ret(r);
    20  }