set O_NONBLOCK flag to stdout

dwl.c

@@ -2190,6 +2190,12 @@ run(char *startup_cmd)
 		close(piperw[1]);
 		close(piperw[0]);
 	}
+
+	/* Mark stdout as non-blocking to avoid people who does not close stdin
+	 * nor consumes it in their startup script getting dwl frozen */
+	if (fd_set_nonblock(STDOUT_FILENO) < 0)
+		close(STDOUT_FILENO);
+
 	printstatus();
 
 	/* At this point the outputs are initialized, choose initial selmon based on

util.c

@@ -3,6 +3,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <fcntl.h>
 
 #include "util.h"
 
@@ -33,3 +34,18 @@ ecalloc(size_t nmemb, size_t size)
 		die("calloc:");
 	return p;
 }
+
+int
+fd_set_nonblock(int fd) {
+	int flags = fcntl(fd, F_GETFL);
+    if (flags < 0) {
+		perror("fcntl(F_GETFL):");
+        return -1;
+    }
+    if (fcntl(fd, F_SETFL, flags | O_NONBLOCK) < 0) {
+		perror("fcntl(F_SETFL):");
+		return -1;
+    }
+
+	return 0;
+}

util.h

@@ -2,3 +2,4 @@
 
 void die(const char *fmt, ...);
 void *ecalloc(size_t nmemb, size_t size);
+int fd_set_nonblock(int fd);