Index: usr.bin/sponge/Makefile
===================================================================
--- /dev/null
+++ usr.bin/sponge/Makefile
@@ -0,0 +1,5 @@
+# $FreeBSD$
+
+PROG=	sponge
+
+.include <bsd.prog.mk>
Index: usr.bin/sponge/sponge.1
===================================================================
--- /dev/null
+++ usr.bin/sponge/sponge.1
@@ -0,0 +1,74 @@
+.\"	Eitan Adler.  All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\" $FreeBSD$
+.\"
+.Dd November 01, 2017
+.Dt SPONGE 1
+.Os
+.Sh NAME
+.Nm sponge
+.Nd buffer stdin and write to stdout
+.Sh SYNOPSIS
+.Nm
+.Op Fl a
+.Ar filename
+.Sh DESCRIPTION
+The
+.Nm
+utility reads standard in until complete, and then opens
+the output file, and then writes to it.
+This makes it valuable in pipelines that write back to the
+same file they read.
+The following options are available:
+.Bl -tag -width indent
+.It Fl a
+Opens
+.Ar filename
+in append mode.
+.El
+.Pp
+In the event that malloc fails
+.Nm
+fails without output.
+.Sh SEE ALSO
+.Xr builtin 1 ,
+.Xr csh 1 ,
+.Xr getrusage 2 ,
+.Xr tee 1
+.Xr wait 2
+.Sh EXIT STATUS
+.Ex -std
+.Sh EXAMPLES
+A
+.Pa file
+can be be sorted 'in place' by executing
+sort file | sponge file
+.Sh HISTORY
+The
+.Nm
+utility was written by
+.An Eitan Adler Aq Mt eadler@FreeBSD.org
+and first appeared
+in
+.Fx 12.0 .
Index: usr.bin/sponge/sponge.c
===================================================================
--- /dev/null
+++ usr.bin/sponge/sponge.c
@@ -0,0 +1,145 @@
+#include <fcntl.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <getopt.h>
+#include <unistd.h>
+#include <sys/uio.h>
+
+#define DEFAULT_BUF_SIZE 16384
+#define DEFAULT_BUF_CNT 12
+
+static int flag_append = 0;
+
+static void usage(void);
+static void* safe_malloc(size_t size);
+static void* safe_calloc(size_t count, size_t size);
+static void* safe_reallocf(void *ptr, size_t size);
+
+static void*
+safe_malloc(size_t size)
+{
+	void* ret;
+	ret = malloc(size);
+	if (ret == NULL) {
+		perror("malloc failed");
+		exit(1);
+	}
+	return ret;
+}
+
+static void*
+safe_calloc(size_t count, size_t size)
+{
+	void* ret;
+	ret = calloc(count, size);
+	if (ret == NULL) {
+		perror("calloc failed");
+		exit(1);
+	}
+	return ret;
+}
+
+static void*
+safe_reallocf(void *ptr, size_t size)
+{
+	void* ret;
+	ret = reallocf(ptr, size);
+	if (ret == NULL) {
+		perror("reallocf failed");
+		exit(1);
+	}
+	return ret;
+}
+
+static void
+usage(void)
+{
+	fprintf(stderr, "usage: sponge [-a] filename\n");
+}
+
+int
+main(int argc, char* argv[])
+{
+	struct iovec *iov;
+	char *buf;
+	char *outfile;
+	ssize_t i;
+	size_t bufcnt;
+	size_t whichbuf;
+	int fd;
+	int openflags = O_WRONLY;
+	int opt;
+
+	while ((opt = getopt(argc, argv, "ah")) != -1) {
+		switch (opt) {
+		case 'a':
+			flag_append=1;
+			break;
+		case 'h':
+			usage();
+			exit(0);
+		case '?':
+		default:
+			usage();
+			exit(1);
+		}
+	}
+
+	if (optind < argc) {
+                outfile = argv[optind];
+	}
+
+
+	bufcnt = DEFAULT_BUF_CNT;
+	whichbuf = 0;
+	iov = safe_calloc(bufcnt, sizeof(*iov));
+
+	while (true) {
+		buf = safe_malloc(DEFAULT_BUF_SIZE);
+		i = read(STDIN_FILENO, buf, DEFAULT_BUF_SIZE);
+		if (whichbuf == bufcnt) {
+			bufcnt *= 2;
+			iov = safe_reallocf(iov, bufcnt * sizeof(*iov));
+		}
+		if (i < 0) {
+			perror("read failed");
+			exit(1);
+		}
+		if (i == 0) {
+			free(buf);
+			break;
+		}
+		iov[whichbuf].iov_base = buf;
+		iov[whichbuf].iov_len = i;
+		whichbuf++;
+		buf = safe_malloc(DEFAULT_BUF_SIZE);
+	}
+
+	if (outfile) {
+		if (flag_append) {
+			openflags |= O_APPEND;
+		} else {
+			openflags |= O_TRUNC;
+		}
+		fd = open(outfile, openflags);
+	}
+	else {
+		fd = STDOUT_FILENO;
+	}
+
+	if (fd < 0) {
+		perror("failed to open");
+		exit(1);
+	}
+
+	i = writev(fd, iov, whichbuf);
+	if (i < 0) {
+		perror("Failed to write");
+		exit(1);
+	}
+
+	if (outfile) {
+		close(fd);
+	}
+}
Index: usr.bin/tee/tee.1
===================================================================
--- usr.bin/tee/tee.1
+++ usr.bin/tee/tee.1
@@ -72,6 +72,8 @@
 except in the event of the
 .Fl i
 option.
+.Sh SEE ALSO
+.Xr sponge 1
 .Sh EXIT STATUS
 .Ex -std
 .Sh STANDARDS