env: Check the status of stdout.

MFC after:	3 days
Sponsored by:	Klara, Inc.
Reviewed by:	markj
Differential Revision:	https://reviews.freebsd.org/D47009

2 files changed, 19 insertions, 0 deletions

diff --git a/usr.bin/env/env.c b/usr.bin/env/env.c
index bb83baee114f..10e333602ee8 100644
--- a/usr.bin/env/env.c
+++ b/usr.bin/env/env.c
@@ -214,6 +214,8 @@ main(int argc, char **argv)
 	}
 	for (ep = environ; *ep; ep++)
 		(void)printf("%s%c", *ep, term);
+	if (fflush(stdout) != 0)
+		err(1, "stdout");
 	exit(0);
 }
 
diff --git a/usr.bin/env/tests/env_test.sh b/usr.bin/env/tests/env_test.sh
index d49765a04f9a..2dc8f1a4c911 100644
--- a/usr.bin/env/tests/env_test.sh
+++ b/usr.bin/env/tests/env_test.sh
@@ -130,6 +130,22 @@ chdir_body()
 		  env -C "${subdir}" pwd
 }
 
+atf_test_case stdout
+stdout_head()
+{
+	atf_set descr "Failure to write to stdout"
+}
+stdout_body()
+{
+	(
+		trap "" PIPE
+		env 2>stderr
+		echo $? >result
+	) | true
+	atf_check -o inline:"1\n" cat result
+	atf_check -o match:"stdout" cat stderr
+}
+
 atf_init_test_cases()
 {
 	atf_add_test_case basic
@@ -140,4 +156,5 @@ atf_init_test_cases()
 	atf_add_test_case altpath
 	atf_add_test_case equal
 	atf_add_test_case chdir
+	atf_add_test_case stdout
 }