core/: tty

Signed-off-by: Ferass El Hafidi <vitali64pmemail@protonmail.com>

2 files changed, 22 insertions, 0 deletions

diff --git a/config.mk b/config.mk
index ec4901a..1585b79 100644
--- a/config.mk
+++ b/config.mk
@@ -32,6 +32,7 @@ CORE=\
 	tail\
 	test\
 	true\
+	tty\
 	uname\
 	unlink\
 	wc
diff --git a/core/tty.c b/core/tty.c
new file mode 100644
index 0000000..2e663e1
--- /dev/null
+++ b/core/tty.c
@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
+#include <stdio.h>
+#include <errno.h>
+#include <unistd.h>
+#include <string.h>
+
+#define REQ_ERRPRINT /* Require errprint() from ../common/common.h */
+#include "../common/common.h"
+
+int main(int, char *argv[]) {
+	char *terminalname = ttyname(STDIN_FILENO);
+	if (errno == ENOTTY) {
+		/* POSIX says that if the stdin isn't a tty then the error shall be 
+		 * written to stdout, not stderr.
+		 */
+		printf("not a tty\n");
+		return 1;
+	} else if (errno) return errprint(argv[0], NULL, errno);
+	printf("%s\n", terminalname);
+	return 0;
+}