1 files changed, 133 insertions, 0 deletions
diff --git a/src/tty.c b/src/tty.c
new file mode 100644
index 0000000..562c4e7
--- /dev/null
+++ b/src/tty.c
@@ -0,0 +1,133 @@
+/* tty -- print the name of the terminal connected to standard input
+   Copyright (C) 1990-2022 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+/* Displays "not a tty" if stdin is not a terminal.
+   Displays nothing if -s option is given.
+   Exit status 0 if stdin is a tty, 1 if not a tty, 2 if usage error,
+   3 if write error.
+
+   Written by David MacKenzie <djm@gnu.ai.mit.edu>.  */
+
+#include <config.h>
+#include <stdio.h>
+#include <getopt.h>
+#include <sys/types.h>
+
+#include "system.h"
+#include "error.h"
+#include "quote.h"
+
+/* Exit statuses.  */
+enum
+  {
+    TTY_STDIN_NOTTY = 1,
+    TTY_FAILURE = 2,
+    TTY_WRITE_ERROR = 3
+  };
+
+/* The official name of this program (e.g., no 'g' prefix).  */
+#define PROGRAM_NAME "tty"
+
+#define AUTHORS proper_name ("David MacKenzie")
+
+/* If true, return an exit status but produce no output. */
+static bool silent;
+
+static struct option const longopts[] =
+{
+  {"silent", no_argument, NULL, 's'},
+  {"quiet", no_argument, NULL, 's'},
+  {GETOPT_HELP_OPTION_DECL},
+  {GETOPT_VERSION_OPTION_DECL},
+  {NULL, 0, NULL, 0}
+};
+
+void
+usage (int status)
+{
+  if (status != EXIT_SUCCESS)
+    emit_try_help ();
+  else
+    {
+      printf (_("Usage: %s [OPTION]...\n"), program_name);
+      fputs (_("\
+Print the file name of the terminal connected to standard input.\n\
+\n\
+  -s, --silent, --quiet   print nothing, only return an exit status\n\
+"), stdout);
+      fputs (HELP_OPTION_DESCRIPTION, stdout);
+      fputs (VERSION_OPTION_DESCRIPTION, stdout);
+      emit_ancillary_info (PROGRAM_NAME);
+    }
+  exit (status);
+}
+
+int
+main (int argc, char **argv)
+{
+  int optc;
+
+  initialize_main (&argc, &argv);
+  set_program_name (argv[0]);
+  setlocale (LC_ALL, "");
+  bindtextdomain (PACKAGE, LOCALEDIR);
+  textdomain (PACKAGE);
+
+  initialize_exit_failure (TTY_WRITE_ERROR);
+  atexit (close_stdout);
+
+  silent = false;
+
+  while ((optc = getopt_long (argc, argv, "s", longopts, NULL)) != -1)
+    {
+      switch (optc)
+        {
+        case 's':
+          silent = true;
+          break;
+
+        case_GETOPT_HELP_CHAR;
+
+        case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
+
+        default:
+          usage (TTY_FAILURE);
+        }
+    }
+
+  if (optind < argc)
+    {
+      error (0, 0, _("extra operand %s"), quote (argv[optind]));
+      usage (TTY_FAILURE);
+    }
+
+  errno = ENOENT;
+
+  if (silent)
+    return isatty (STDIN_FILENO) ? EXIT_SUCCESS : TTY_STDIN_NOTTY;
+
+  int status = EXIT_SUCCESS;
+  char const *tty = ttyname (STDIN_FILENO);
+
+  if (! tty)
+    {
+      tty = _("not a tty");
+      status = TTY_STDIN_NOTTY;
+    }
+
+  puts (tty);
+  return status;
+}