sponge: Fix bug in -a mode that doubled original content of file

Occurred when the temp file is located on a different filesystem.
It seems that append mode was put in on that file open without realizing
the consequences of it. Bug has been present since the first -a patch.

This commit was sponsored by Peter on Patreon.

2 files changed, 3 insertions, 1 deletions

diff --git a/debian/changelog b/debian/changelog
index 3a62905..f933dc7 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -4,6 +4,8 @@ moreutils (0.63) UNRELEASED; urgency=medium
     Thanks, Stig Palmquist.
   * ts: Fix ts -m %.s to not output negative microseconds.
     Thanks, Dima Kogan
+  * sponge: Fix bug in -a mode that doubled original content of file when
+    the temp file is located on a different filesystem.
 
  -- Joey Hess <id@joeyh.name>  Wed, 22 Aug 2018 21:00:58 -0400
 
diff --git a/sponge.c b/sponge.c
index 09d3971..f852ad5 100644
--- a/sponge.c
+++ b/sponge.c
@@ -372,7 +372,7 @@ int main (int argc, char **argv) {
 		}
 		else {	
 			/* Fall back to slow copy. */
-			outfile = fopen(outname, append ? "a" : "w");
+			outfile = fopen(outname, "w");
 			if (!outfile) {
 				perror("error opening output file");
 				exit(1);