diff --git a/sys/include/bio.h b/sys/include/bio.h
index 776f7b0f5..157e525c4 100644
--- a/sys/include/bio.h
+++ b/sys/include/bio.h
@@ -59,6 +59,7 @@ int	Binits(Biobufhdr*, int, int, uchar*, int);
 int	Blinelen(Biobufhdr*);
 vlong	Boffset(Biobufhdr*);
 Biobuf*	Bopen(char*, int);
+Biobuf*	Bfdopen(int, int);
 int	Bprint(Biobufhdr*, char*, ...);
 int	Bvprint(Biobufhdr*, char*, va_list);
 int	Bputc(Biobufhdr*, int);
diff --git a/sys/man/2/bio b/sys/man/2/bio
index a059f1cf4..1aae56005 100644
--- a/sys/man/2/bio
+++ b/sys/man/2/bio
@@ -1,6 +1,6 @@
 .TH BIO 2
 .SH NAME
-Bopen, Binit, Binits, Brdline, Brdstr, Bgetc, Bgetrune, Bgetd, Bungetc, Bungetrune, Bread, Bseek, Boffset, Bfildes, Blinelen, Bputc, Bputrune, Bprint, Bvprint, Bwrite, Bflush, Bterm, Bbuffered, Blethal \- buffered input/output
+Bopen, Bfdopen, Binit, Binits, Brdline, Brdstr, Bgetc, Bgetrune, Bgetd, Bungetc, Bungetrune, Bread, Bseek, Boffset, Bfildes, Blinelen, Bputc, Bputrune, Bprint, Bvprint, Bwrite, Bflush, Bterm, Bbuffered, Blethal \- buffered input/output
 .SH SYNOPSIS
 .ta \w'Biobuf* 'u
 .B #include <u.h>
@@ -13,6 +13,9 @@ Bopen, Binit, Binits, Brdline, Brdstr, Bgetc, Bgetrune, Bgetd, Bungetc, Bungetru
 Biobuf* Bopen(char *file, int mode)
 .PP
 .B
+Biobuf* Bfdopen(int fd, int mode)
+.PP
+.B
 int	Binit(Biobuf *bp, int fd, int mode)
 .PP
 .B
@@ -96,6 +99,17 @@ It calls
 .IR malloc (2)
 to allocate a buffer.
 .PP
+.I Bfdopen
+allocates a buffer for the already-open file descriptor
+.I fd
+for mode
+.B OREAD
+or
+.BR OWRITE .
+It calls
+.IR malloc (2)
+to allocate a buffer.
+.PP
 .I Binit
 initializes a standard size buffer, type
 .IR Biobuf ,
diff --git a/sys/src/libbio/binit.c b/sys/src/libbio/binit.c
index 36ed50ace..9afae5b34 100644
--- a/sys/src/libbio/binit.c
+++ b/sys/src/libbio/binit.c
@@ -53,7 +53,6 @@ install(Biobufhdr *bp)
 int
 Binits(Biobufhdr *bp, int f, int mode, uchar *p, int size)
 {
-
 	p += Bungetsize;	/* make room for Bungets */
 	size -= Bungetsize;
 
@@ -94,29 +93,48 @@ Binit(Biobuf *bp, int f, int mode)
 	return Binits(bp, f, mode, bp->b, sizeof(bp->b));
 }
 
+Biobuf*
+Bfdopen(int fd, int mode)
+{
+	Biobuf *bp;
+
+	bp = malloc(sizeof(Biobuf));
+	if(bp == nil)
+		return nil;
+	if(Binits(bp, fd, mode, bp->b, sizeof(bp->b)) != 0){
+		free(bp);
+		return nil;
+	}
+	bp->flag = Bmagic;			/* mark bp open & malloced */
+	setmalloctag(bp, getcallerpc(&fd));
+	return bp;
+}
+
 Biobuf*
 Bopen(char *name, int mode)
 {
 	Biobuf *bp;
-	int f;
+	int fd;
 
 	switch(mode&~(OCEXEC|ORCLOSE|OTRUNC)) {
 	default:
 		fprint(2, "Bopen: unknown mode %#x\n", mode);
-		return 0;
+		return nil;
 	case OREAD:
-		f = open(name, mode);
+		fd = open(name, mode);
 		break;
 	case OWRITE:
-		f = create(name, mode, 0666);
+		fd = create(name, mode, 0666);
 		break;
 	}
-	if(f < 0)
-		return 0;
-	bp = malloc(sizeof(Biobuf));
+	if(fd < 0)
+		return nil;
+	bp = Bfdopen(fd, mode);
+	if(bp == nil){
+		close(fd);
+		return nil;
+	}
 	setmalloctag(bp, getcallerpc(&name));
-	Binits(bp, f, mode, bp->b, sizeof(bp->b));
-	bp->flag = Bmagic;			/* mark bp open & malloced */
 	return bp;
 }