timer.c: Use SIGWINCH handler to get term_width when changed.

timer.c no longer spams ioctl TIOCGWINSZ 4 times a second, it now
handles SIGWINCH and sets a file scope variable to the width.

1 files changed, 23 insertions, 7 deletions

diff --git a/timer.c b/timer.c
index 875cb5c..87c90a3 100644
--- a/timer.c
+++ b/timer.c
@@ -30,6 +30,19 @@
 #define SEC_YEAR   31556940
 
 static const unsigned long interval_nsec = 1000000000 / 4;
+unsigned short term_width = 0; /* Maybe volatile? */
+
+void sigwinch(int sig) {
+	if (sig != SIGWINCH)
+		return;
+
+	struct winsize ws;
+
+	if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws) == -1)
+		error(1, errno, "Failed to get terminal width");
+
+	term_width = ws.ws_col;
+}
 
 unsigned long int get_seconds(char *code)
 {
@@ -67,15 +80,10 @@ unsigned long int get_seconds(char *code)
 
 void clear_line(void)
 {
-	struct winsize ws;
-
-	if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws) == -1)
-		error(1, errno, "IOCTL failed");
-
-	if (ws.ws_col <= 1)
+	if (term_width <= 1)
 		return;
 
-	for (unsigned short i = 0; i < ws.ws_col - 1; i++)
+	for (unsigned short i = 0; i < term_width - 1; i++)
 		putchar(' ');
 
 	putchar('\r');
@@ -152,6 +160,7 @@ int main(int argc, char **argv)
 	sigset_t sigset;
 	struct itimerspec its;
 	struct sigevent sev;
+	struct sigaction sigact;
 	timer_t timerid;
 
 	unsigned long total_seconds = 0;
@@ -165,6 +174,11 @@ int main(int argc, char **argv)
 	for (int i = 1; i < argc; i++)
 		total_seconds += get_seconds(argv[i]);
 
+	sigact.sa_handler = sigwinch;
+
+	if (sigaction(SIGWINCH, &sigact, NULL) != 0)
+		error(1, errno, "Unable to set SIGWINCH signal action");
+
 	sev.sigev_notify = SIGEV_SIGNAL;
 	sev.sigev_signo = SIGRTMIN;
 	sev.sigev_value.sival_ptr = &timerid;
@@ -189,6 +203,8 @@ int main(int argc, char **argv)
 	if (timer_settime(timerid, 0, &its, NULL) != 0)
 		error(1, errno, "Could not set timer");
 
+	sigwinch(SIGWINCH);
+
 	for (unsigned long i = 0; i < total_seconds; i++)
 		for (int ii = 0; ii < 4; ii++) {
 			if (sigwait(&sigset, &sig), sig != SIGRTMIN)