From 85f37eb9f6fd8b633d312dbd5471d06a75762956 Mon Sep 17 00:00:00 2001
From: Thomas Voss <mail@thomasvoss.com>
Date: Fri, 7 Jun 2024 00:06:49 +0200
Subject: Add cloexec

---
 c/cloexec/.gitignore |  1 +
 c/cloexec/Makefile   |  8 ++++++++
 c/cloexec/cloexec.c  | 26 ++++++++++++++++++++++++++
 3 files changed, 35 insertions(+)
 create mode 100644 c/cloexec/.gitignore
 create mode 100644 c/cloexec/Makefile
 create mode 100644 c/cloexec/cloexec.c

diff --git a/c/cloexec/.gitignore b/c/cloexec/.gitignore
new file mode 100644
index 0000000..089a255
--- /dev/null
+++ b/c/cloexec/.gitignore
@@ -0,0 +1 @@
+cloexec
diff --git a/c/cloexec/Makefile b/c/cloexec/Makefile
new file mode 100644
index 0000000..1c57a62
--- /dev/null
+++ b/c/cloexec/Makefile
@@ -0,0 +1,8 @@
+include ../base.mk
+
+all: cloexec
+cloexec: cloexec.c
+	$(CC) $(CFLAGS) -o $@ $<
+
+clean:
+	rm -f cloexec
diff --git a/c/cloexec/cloexec.c b/c/cloexec/cloexec.c
new file mode 100644
index 0000000..ba899ee
--- /dev/null
+++ b/c/cloexec/cloexec.c
@@ -0,0 +1,26 @@
+#define _GNU_SOURCE
+#include <assert.h>
+#include <err.h>
+#include <paths.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+int
+main(void)
+{
+	int fd, nfd;
+
+	if ((fd = open(_PATH_DEVNULL, O_RDONLY | O_CLOEXEC)) == -1)
+		err(1, "open: %s", _PATH_DEVNULL);
+
+	if ((nfd = dup(fd)) == -1)
+		err(1, "dup");
+	assert((fcntl(nfd, F_GETFD) & FD_CLOEXEC) == 0);
+	close(nfd);
+	if (dup3(fd, nfd, O_CLOEXEC) == -1)
+		err(1, "dup");
+	assert((fcntl(nfd, F_GETFD) & FD_CLOEXEC) != 0);
+
+	close(nfd);
+	close(fd);
+}
-- 
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