commit 3565860b40ea4a8220d5029e3d74b437a9205cda
Author: Jakob Kramer <jakob.kramer@gmx.de>
Date:   Tue Jun 25 19:55:37 2013 +0200

    added sponge

diff --git a/Makefile b/Makefile
index 9aeb5c4..7f91bac 100644
--- a/Makefile
+++ b/Makefile
@@ -61,6 +61,7 @@ SRC = \
 	sleep.c    \
 	sort.c     \
 	split.c    \
+	sponge.c   \
 	sync.c     \
 	tail.c     \
 	tee.c      \
diff --git a/sponge.1 b/sponge.1
new file mode 100644
index 0000000..8c09cc7
--- /dev/null
+++ b/sponge.1
@@ -0,0 +1,11 @@
+.TH SPONGE 1 sbase\-VERSION
+.SH NAME
+sponge \- soak up standard input and write to a file
+.SH SYNOPSIS
+.B sponge
+.RI [ file ]
+.SH DESCRIPTION
+.B sponge
+reads stdin and writes to the specified file or stdout otherwise. This
+makes it possible to easily create pipes which read from and write to
+the same file.
diff --git a/sponge.c b/sponge.c
new file mode 100644
index 0000000..c116905
--- /dev/null
+++ b/sponge.c
@@ -0,0 +1,46 @@
+/* See LICENSE file for copyright and license details. */
+#include <stdio.h>
+
+#include "util.h"
+
+int
+main(int argc, char *argv[])
+{
+	FILE *fp, *tmpfp;
+	char *tmp_nam, buf[BUFSIZ];
+	size_t n;
+
+	ARGBEGIN {
+	default:
+		eprintf("usage: %s [file]\n", argv0);
+	} ARGEND;
+
+	if(argc == 0)
+		/* maybe it’s better to just redirect stdin > stdout
+		 * directly, in this case */
+		fp = stdout;
+	else if(argc == 1)
+		if(!(fp = fopen(argv[0], "w")))
+			eprintf("fopen %s:", argv[0]);
+
+	if(!(tmp_nam = tmpnam(NULL)))
+		eprintf("tmpnam:");
+
+	if(!(tmpfp = fopen(tmp_nam, "w")))
+		eprintf("fopen %s:", tmp_nam);
+
+	while((n = fread(buf, 1, sizeof buf, stdin)) > 0) {
+		if(fwrite(buf, 1, n, (fp == stdout ? stdout : tmpfp)) != n)
+			eprintf("%s: write error:", buf);
+	}
+
+	if(fp != stdout)
+		if(rename(tmp_nam, argv[0])) {
+			eprintf("could not create file:");
+			fclose(fp);
+		}
+
+	fclose(tmpfp);
+
+	return 0;
+}