[RFC PATCH] gpioset: only print prompt when stdout is tty

[Esben Haabendal <esben@xxxxxxxxxx>]

When gpioset interactive mode is used as intended, as a human controlled
interface, stdout should be a tty.

By leaving out the prompt when stdout is not a tty, gpioset interactive mode can
be used as a really simple deamon for controlling GPIOs by connecting it to a
FIFO.

Signed-off-by: Esben Haabendal <esben@xxxxxxxxxx>
---
 tools/gpioset.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/tools/gpioset.c b/tools/gpioset.c
index 9dc5aeb8b286..a1ca211febd7 100644
--- a/tools/gpioset.c
+++ b/tools/gpioset.c
@@ -742,13 +742,12 @@ static void interact(struct gpiod_line_request **requests,
 {
 	int num_words, num_lines, max_words, period_us, i;
 	char *line, **words, *line_buf;
-	bool done, stdout_is_tty;
+	bool done;
 
 	stifle_history(20);
 	rl_attempted_completion_function = tab_completion;
 	rl_basic_word_break_characters = " =\"";
 	completion_context = resolver;
-	stdout_is_tty = isatty(1);
 
 	max_words = resolver->num_lines + 1;
 	words = calloc(max_words, sizeof(*words));
@@ -757,12 +756,9 @@ static void interact(struct gpiod_line_request **requests,
 
 	for (done = false; !done;) {
 		/*
-		 * manually print the prompt, as libedit doesn't if stdout
-		 * is not a tty.  And fflush to ensure the prompt and any
-		 * output buffered from the previous command is sent.
+		 * fflush to ensure the prompt and any output buffered from the
+		 * previous command is sent.
 		 */
-		if (!stdout_is_tty)
-			printf(PROMPT);
 		fflush(stdout);
 
 		line = readline(PROMPT);
-- 
2.40.1