/contrib/cvs/lib/dup2.c

 1/*
 2	dup2 -- 7th Edition UNIX system call emulation for UNIX System V
 3
 4	last edit:	11-Feb-1987	D A Gwyn
 5*/
 6
 7#ifdef HAVE_CONFIG_H
 8#include "config.h"
 9#endif
10
11#include	<errno.h>
12#include	<fcntl.h>
13
14extern int	close(), fcntl();
15
16int
17dup2( oldfd, newfd )
18	int		oldfd;		/* already-open file descriptor */
19	int		newfd;		/* desired duplicate descriptor */
20{
21	register int	ret;		/* for fcntl() return value */
22	register int	save;		/* for saving entry errno */
23
24	if ( oldfd == newfd )
25		return oldfd;		/* be careful not to close() */
26
27	save = errno;			/* save entry errno */
28	(void) close( newfd );		/* in case newfd is open */
29	/* (may have just clobbered the original errno value) */
30
31	ret = fcntl( oldfd, F_DUPFD, newfd );	/* dupe it */
32
33	if ( ret >= 0 )
34		errno = save;		/* restore entry errno */
35	else				/* fcntl() returned error */
36		if ( errno == EINVAL )
37			errno = EBADF;	/* we think of everything */
38
39	return ret;			/* return file descriptor */
40}