From d2620c60c54761c09dc679f2db07c296c355436a Mon Sep 17 00:00:00 2001
From: Kirill Primak <vyivel@eclair.cafe>
Date: Wed, 6 Nov 2024 23:38:01 +0300
Subject: [PATCH] main: refuse to dump the result into tty

Closes: https://codeberg.org/vyivel/dulcepan/issues/17
---
 src/main.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/src/main.c b/src/main.c
index 1f16cdf..660d9e4 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,6 +1,7 @@
 #include <getopt.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 #include <wayland-client-core.h>
 #include <wayland-client-protocol.h>
 #include <xkbcommon/xkbcommon.h>
@@ -167,8 +168,9 @@ static void help(const char *prog) {
 			"  -o <path>    Specify the output file path.\n"
 			"\n"
 			"If the output file path is not specified, the resuling image will be printed to\n"
-			"the standard output. If the output file format is not specified, it is guessed\n"
-			"from the output file path if it's specified, and assumed to be PNG otherwise.\n"
+			"the standard output, which is expected to not be a terminal. If the output file\n"
+			"format is not specified, it is guessed from the output file path if it's\n"
+			"specified, and assumed to be PNG otherwise.\n"
 			"\n"
 			"Supported formats: png, ppm.\n"
 			"\n"
@@ -210,6 +212,14 @@ int main(int argc, char **argv) {
 		}
 	}
 
+	if (state.output_path == NULL && isatty(STDOUT_FILENO)) {
+		fprintf(stderr,
+				"Refusing to run as the standard output is a terminal and there's no output file\n"
+				"path specified.\n\n");
+		help(argv[0]);
+		exit(1);
+	}
+
 	if (state.output_format == DP_FILE_UNKNOWN) {
 		if (state.output_path != NULL) {
 			const char *ext = dp_ext_from_path(state.output_path);