Add '-w' option to tigger based on window is resize signals

Response is similar to <space> keyboard input, except it cannot
not be combined with the '-r' flag.

Author: eradman

entr.1

@@ -13,7 +13,7 @@
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
-.Dd February 6, 2025
+.Dd June 25, 2025
 .Dt ENTR 1
 .Os
 .Sh NAME
@@ -86,6 +86,10 @@ Control of the TTY is not transferred to the child process.
 Evaluate the first argument using the interpreter specified by the
 .Ev SHELL
 environment variable.
+.It Fl w
+Execute the
+.Ar utility
+if the terminal is resized.
 .It Fl x
 Format custom exit status messages using a persistent
 .Xr awk 1

entr.c

@@ -71,6 +71,7 @@ int oneshot_opt;
 int postpone_opt;
 int restart_opt;
 int shell_opt;
+int winch_opt;
 int status_filter_opt;
 
 int termios_set;
@@ -84,6 +85,7 @@ static char *argv0, *argv0_base;
 static void usage();
 static void terminate_utility();
 static void handle_exit(int sig);
+static void handle_winch(int sig);
 static void proc_exit(int sig);
 static void print_child_status(int status);
 static int process_input(FILE *, WatchFile *[], int);
@@ -230,7 +232,7 @@ main(int argc, char *argv[]) {
 void
 usage() {
 	fprintf(stderr, "release: %s\n", RELEASE);
-	fprintf(stderr, "usage: entr [-acdnprsxz] utility [argument [/_] ...] < filenames\n");
+	fprintf(stderr, "usage: entr [-acdnprswxz] utility [argument [/_] ...] < filenames\n");
 	exit(1);
 }
 
@@ -267,6 +269,11 @@ handle_exit(int sig) {
 		raise(sig);
 }
 
+void
+handle_winch(int sig) {
+	return;
+}
+
 void
 proc_exit(int sig) {
 	int status;
@@ -411,7 +418,7 @@ set_options(char *argv[]) {
 	/* read arguments until we reach a command */
 	for (argc = 1; argv[argc] != 0 && argv[argc][0] == '-'; argc++)
 		;
-	while ((ch = getopt(argc, argv, "acdnprsxz")) != -1) {
+	while ((ch = getopt(argc, argv, "acdnprswxz")) != -1) {
 		switch (ch) {
 		case 'a':
 			aggressive_opt = 1;
@@ -434,6 +441,9 @@ set_options(char *argv[]) {
 		case 's':
 			shell_opt = 1;
 			break;
+		case 'w':
+			winch_opt = 1;
+			break;
 		case 'x':
 			status_filter_opt = status_filter_opt ? 2 : 1;
 			break;
@@ -450,6 +460,9 @@ set_options(char *argv[]) {
 	if (status_filter_opt && restart_opt)
 		errx(1, "-r and -x may not be combined");
 
+	if (winch_opt && restart_opt)
+		errx(1, "-r and -w may not be combined");
+
 	if ((shell_opt == 1) && (argv[optind + 1] != 0))
 		errx(1, "-s requires commands to be formatted as a single argument");
 	return optind;
@@ -624,6 +637,7 @@ watch_loop(int kq, char *argv[]) {
 	int nev;
 	WatchFile *file;
 	int i;
+	struct sigaction act;
 	struct timespec evTimeout = { 0, 1000000 };
 	int reopen_only = !aggressive_opt;
 	int collate_only = 0;
@@ -634,7 +648,9 @@ watch_loop(int kq, char *argv[]) {
 	char c;
 	struct termios character_tty;
 
+	sigemptyset(&act.sa_mask);
 	leading_edge = files[0]; /* default */
+
 	if (postpone_opt == 0)
 		run_utility(argv);
 
@@ -653,12 +669,26 @@ watch_loop(int kq, char *argv[]) {
 	if ((reopen_only == 1) || (collate_only == 1)) {
 		nev = kevent(kq, NULL, 0, evList, 32, &evTimeout);
 	} else {
+		/* interrupt kevent if terminal resized */
+		if (winch_opt == 1) {
+			act.sa_flags = SA_RESETHAND;
+			act.sa_handler = handle_winch;
+			if (sigaction(SIGWINCH, &act, NULL) != 0)
+				err(1, "Failed to set SIGWINCH handler");
+		}
+
+		/* wait for events */
 		nev = kevent(kq, NULL, 0, evList, 32, NULL);
 		dir_modified = 0;
 	}
 
-	if ((nev == -1) && (errno != EINTR))
-		warn("kevent failed");
+	if (nev == -1) {
+		if (errno == EINTR) {
+			if (winch_opt == 1)
+				do_exec = 1;
+		} else
+			warn("kevent");
+	}
 
 	for (i = 0; i < nev; i++) {
 		if (!noninteractive_opt && evList[i].filter == EVFILT_READ) {

system_test.sh

@@ -178,6 +178,18 @@ try "spacebar triggers utility"
 	tmux send-keys -t $tsession:0 "q" ; zz
 	tmux kill-session -t $tsession
 
+# signal tests
+
+try "exec utility when the terminal is resized"
+	setup
+	ls $tmp/file* | entr -pws 'printf ping' > $tmp/exec.out &
+	bgpid=$! ; zz
+	kill -WINCH $bgpid ; zz
+	echo "123" > $tmp/file1 ; zz
+	kill -INT $bgpid
+	wait $bgpid; assert "$?" "0"
+	assert "$(cat $tmp/exec.out)" "pingping"
+
 # file system tests
 
 try "exec a command using one-shot option"