add ptty tool for testing

ptty: starts program within a pseudo tty for
non-tty test environments

Makefile

@@ -10,9 +10,9 @@ install: scroll
 	cp scroll ${BINDIR}
 	cp scroll.1 ${MAN1DIR}
 
-test: scroll
+test: scroll ptty
 	# check usage
-	if ./scroll; then exit 1; fi
+	if ./ptty ./scroll; then exit 1; fi
 	# check exit passthrough of child
-	if ! ./scroll true;  then exit 1; fi
-	if   ./scroll false; then exit 1; fi
+	if ! ./ptty ./scroll true;  then exit 1; fi
+	if   ./ptty ./scroll false; then exit 1; fi

ptty.c

@@ -0,0 +1,90 @@
+#include <sys/wait.h>
+
+#include <errno.h>
+#include <inttypes.h>
+#include <limits.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <termios.h>
+#include <unistd.h>
+#include <util.h>
+
+void
+die(const char *fmt, ...)
+{
+	va_list ap;
+	va_start(ap, fmt);
+	vfprintf(stderr, fmt, ap);
+	va_end(ap);
+
+	if (fmt[0] && fmt[strlen(fmt)-1] == ':') {
+		fputc(' ', stderr);
+		perror(NULL);
+	} else {
+		fputc('\n', stderr);
+	}
+
+	exit(EXIT_FAILURE);
+}
+
+void
+usage(void)
+{
+	fputs("ptty cmd\n", stderr);
+	exit(EXIT_FAILURE);
+}
+
+int
+main(int argc, char *argv[])
+{
+	struct winsize ws = {.ws_row = 25, .ws_col = 80, 0, 0};
+	int ch;
+
+	while ((ch = getopt(argc, argv, "c:r:h")) != -1) {
+		switch (ch) {
+		case 'c':	/* cols */
+			ws.ws_col = strtoimax(optarg, NULL, 10);
+			if (errno != 0)
+				die("strtoimax: %s", optarg);
+			break;
+		case 'r':	/* lines */
+			ws.ws_row = strtoimax(optarg, NULL, 10);
+			if (errno != 0)
+				die("strtoimax: %s", optarg);
+			break;
+		case 'h':
+		default:
+			usage();
+		}
+	}
+	argc -= optind;
+	argv += optind;
+
+	if (argc < 1)
+		usage();
+
+	int mfd;
+	pid_t pid = forkpty(&mfd, NULL, NULL, &ws);
+	switch (pid) {
+	case -1:
+		die("forkpty");
+	case  0: /* child */
+		execvp(argv[0], argv);
+		die("exec");
+	}
+
+	/* parent */
+	FILE *fh = fdopen(mfd, "rw");
+	if (fh == NULL)
+		die("fdopen");
+
+	char buf[BUFSIZ];
+	while (fgets(buf, sizeof buf, fh) != NULL);
+
+	int status;
+	waitpid(pid, &status, 0);
+
+	return WEXITSTATUS(status);
+}