Add tty(1).

utils/.gitignore

@@ -49,6 +49,7 @@ time
 touch
 tr
 true
+tty
 type
 uname
 uniq

utils/Makefile

@@ -60,6 +60,7 @@ time \
 touch \
 tr \
 true \
+tty \
 type \
 uname \
 uniq \

utils/tty.c

@@ -0,0 +1,74 @@
+/*
+ * Copyright (c) 2014, 2015 Jonas 'Sortie' Termansen.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ * tty.c
+ * Print terminal's name.
+ */
+
+#include <err.h>
+#include <errno.h>
+#include <string.h>
+#include <stdio.h>
+#include <unistd.h>
+
+static void compact_arguments(int* argc, char*** argv)
+{
+	for ( int i = 0; i < *argc; i++ )
+	{
+		while ( i < *argc && !(*argv)[i] )
+		{
+			for ( int n = i; n < *argc; n++ )
+				(*argv)[n] = (*argv)[n+1];
+			(*argc)--;
+		}
+	}
+}
+
+int main(int argc, char* argv[])
+{
+	for ( int i = 1; i < argc; i++ )
+	{
+		const char* arg = argv[i];
+		if ( arg[0] != '-' || !arg[1] )
+			continue;
+		argv[i] = NULL;
+		if ( !strcmp(arg, "--") )
+			break;
+		if ( arg[1] != '-' )
+		{
+			char c;
+			while ( (c = *++arg) ) switch ( c )
+			{
+			default:
+				errx(2, "unknown option -- '%c'", c);
+			}
+		}
+		else
+			errx(2, "unknown option: %s", arg);
+	}
+
+	compact_arguments(&argc, &argv);
+
+	if ( 1 < argc )
+		errx(1, "unexpected extra operand");
+
+	char* name = ttyname(0);
+	if ( !name && errno != ENOTTY )
+		err(2, "ttyname");
+	puts(name ? name : "not a tty");
+	if ( ferror(stdout) || fflush(stdout) == EOF )
+		return 2;
+	return name ? 1 : 0;
+}