Add -1 flag (single instance)

docs/wmenu.1.scd

@@ -6,7 +6,7 @@ wmenu - dynamic menu for Wayland
 
 # SYNOPSIS
 
-*wmenu* [-biPv] \
+*wmenu* [-1biPv] \
   [-f _font_] \
   [-l _lines_] \
   [-o _output_] \
@@ -29,6 +29,9 @@ $PATH and runs the result.
 
 # OPTIONS
 
+*-1*
+	allow only one instance.
+
 *-b*
 	wmenu appears at the bottom of the screen.
 

menu.c

@@ -85,12 +85,15 @@ static bool parse_color(const char *color, uint32_t *result) {
 // Parse menu options from command line arguments.
 void menu_getopts(struct menu *menu, int argc, char *argv[]) {
 	const char *usage =
-		"Usage: wmenu [-biPv] [-f font] [-l lines] [-o output] [-p prompt]\n"
+		"Usage: wmenu [-1biPv] [-f font] [-l lines] [-o output] [-p prompt]\n"
 		"\t[-N color] [-n color] [-M color] [-m color] [-S color] [-s color]\n";
 
 	int opt;
-	while ((opt = getopt(argc, argv, "bhiPvf:l:o:p:N:n:M:m:S:s:")) != -1) {
+	while ((opt = getopt(argc, argv, "1bhiPvf:l:o:p:N:n:M:m:S:s:")) != -1) {
 		switch (opt) {
+		case '1':
+			menu->single_instance = true;
+			break;
 		case 'b':
 			menu->bottom = true;
 			break;

menu.h

@@ -29,6 +29,8 @@ struct page {
 
 // Menu state.
 struct menu {
+	// Allow only one instance
+	bool single_instance;
 	// Whether the menu appears at the bottom of the screen
 	bool bottom;
 	// The function used to match menu items

wmenu-run.c

@@ -4,6 +4,8 @@
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
+#include <fcntl.h>
+#include <sys/file.h>
 
 #include "menu.h"
 #include "wayland.h"
@@ -71,6 +73,23 @@ static void exec_item(struct menu *menu, char *text, bool exit) {
 int main(int argc, char *argv[]) {
 	struct menu *menu = menu_create(exec_item);
 	menu_getopts(menu, argc, argv);
+	if (menu->single_instance) {
+		// the following code was copied from `bemenu`, thanks.
+		char *xdg_runtime_dir = getenv("XDG_RUNTIME_DIR");
+
+	        char buffer[1024];
+		char *menu_lock_location = (xdg_runtime_dir == NULL ? "/tmp" : xdg_runtime_dir);
+	        snprintf(buffer, sizeof(buffer), "%s/wmenu.lock", menu_lock_location);
+
+		// Create a read-write lock file(if not already exists),
+		// closes on exec. Creates in tmp due to permissions.
+		int menu_lock = open(buffer, O_CREAT | O_RDWR | O_CLOEXEC, 0666);
+		// If we cannot set the lock/the lock is already present.
+		if (flock(menu_lock, LOCK_EX | LOCK_NB) == -1) {
+		    fprintf(stderr, "\"%s\" instance is already running\n", argv[0]);
+		    exit(EXIT_FAILURE);
+		}
+	    }
 	read_items(menu);
 	int status = menu_run(menu);
 	menu_destroy(menu);

wmenu.c

@@ -1,7 +1,10 @@
 #define _POSIX_C_SOURCE 200809L
 
+#include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
+#include <fcntl.h>
+#include <sys/file.h>
 
 #include "menu.h"
 #include "wayland.h"
@@ -28,6 +31,23 @@ static void print_item(struct menu *menu, char *text, bool exit) {
 int main(int argc, char *argv[]) {
 	struct menu *menu = menu_create(print_item);
 	menu_getopts(menu, argc, argv);
+	if (menu->single_instance) {
+		// the following code was copied from `bemenu`, thanks.
+		char *xdg_runtime_dir = getenv("XDG_RUNTIME_DIR");
+
+	        char buffer[1024];
+		char *menu_lock_location = (xdg_runtime_dir == NULL ? "/tmp" : xdg_runtime_dir);
+	        snprintf(buffer, sizeof(buffer), "%s/wmenu.lock", menu_lock_location);
+
+		// Create a read-write lock file(if not already exists),
+		// closes on exec. Creates in tmp due to permissions.
+		int menu_lock = open(buffer, O_CREAT | O_RDWR | O_CLOEXEC, 0666);
+		// If we cannot set the lock/the lock is already present.
+		if (flock(menu_lock, LOCK_EX | LOCK_NB) == -1) {
+		    fprintf(stderr, "\"%s\" instance is already running\n", argv[0]);
+		    exit(EXIT_FAILURE);
+		}
+	    }
 	read_items(menu);
 	int status = menu_run(menu);
 	menu_destroy(menu);