--- /sys/include/bio.h
+++ /sys/include/bio.h
@@ -58,6 +58,7 @@ 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);
--- /sys/man/2/bio
+++ /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 \- 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 \- 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
@@ -93,6 +96,17 @@ 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 ,
@@ -138,7 +152,9 @@ and returns
 .IR Bflush 's
 return value.
 If the buffer was allocated by
-.IR Bopen ,
+.I Bopen
+or
+.IR Bfdopen ,
 the buffer is
 .I freed
 and the file is closed.
--- /sys/src/libbio/binit.c
+++ /sys/src/libbio/binit.c
@@ -93,6 +93,22 @@ Binit(Biobuf *bp, int f, int mode)
 	return Binits(bp, f, mode, bp->b, sizeof(bp->b));
 }
 
+Biobuf*
+Bfdopen(int f, int mode)
+{
+	Biobuf *bp;
+
+	bp = malloc(sizeof(Biobuf));
+	if(bp == 0)
+		return 0;
+	if(Binits(bp, f, mode, bp->b, sizeof(bp->b)) != 0){
+		free(bp);
+		return 0;
+	}
+	bp->flag = Bmagic;			/* mark bp open & malloced */
+	return bp;
+}
+
 Biobuf*
 Bopen(char *name, int mode)
 {
@@ -112,9 +128,9 @@ Bopen(char *name, int mode)
 	}
 	if(f < 0)
 		return 0;
-	bp = malloc(sizeof(Biobuf));
-	Binits(bp, f, mode, bp->b, sizeof(bp->b));
-	bp->flag = Bmagic;			/* mark bp open & malloced */
+	bp = Bfdopen(f, mode);
+	if(bp == 0)
+		close(f);
 	return bp;
 }