[unix-history] / .ref-386BSD-0.1-patchkit / usr / othersrc / public / cvs-1.3 / lib / dup2.c

/*
	dup2 -- 7th Edition UNIX system call emulation for UNIX System V

	last edit:	11-Feb-1987	D A Gwyn
*/

#include	<errno.h>
#include	<fcntl.h>

extern int	close(), fcntl();

int
dup2( oldfd, newfd )
	int		oldfd;		/* already-open file descriptor */
	int		newfd;		/* desired duplicate descriptor */
{
	register int	ret;		/* for fcntl() return value */
	register int	save;		/* for saving entry errno */

	if ( oldfd == newfd )
		return oldfd;		/* be careful not to close() */

	save = errno;			/* save entry errno */
	(void) close( newfd );		/* in case newfd is open */
	/* (may have just clobbered the original errno value) */

	ret = fcntl( oldfd, F_DUPFD, newfd );	/* dupe it */

	if ( ret >= 0 )
		errno = save;		/* restore entry errno */
	else				/* fcntl() returned error */
		if ( errno == EINVAL )
			errno = EBADF;	/* we think of everything */

	return ret;			/* return file descriptor */
}
Commit	Line	Data
44b4867e WJ	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	#include <errno.h>
	8	#include <fcntl.h>
	9
	10	extern int close(), fcntl();
	11
	12	int
	13	dup2( oldfd, newfd )
	14	int oldfd; /* already-open file descriptor */
	15	int newfd; /* desired duplicate descriptor */
	16	{
	17	register int ret; /* for fcntl() return value */
	18	register int save; /* for saving entry errno */
	19
	20	if ( oldfd == newfd )
	21	return oldfd; /* be careful not to close() */
	22
	23	save = errno; /* save entry errno */
	24	(void) close( newfd ); /* in case newfd is open */
	25	/* (may have just clobbered the original errno value) */
	26
	27	ret = fcntl( oldfd, F_DUPFD, newfd ); /* dupe it */
	28
	29	if ( ret >= 0 )
	30	errno = save; /* restore entry errno */
	31	else /* fcntl() returned error */
	32	if ( errno == EINVAL )
	33	errno = EBADF; /* we think of everything */
	34
	35	return ret; /* return file descriptor */
	36	}