swaygrab: add default output filename.

With this it's possible to run `swaygrab` without a filename argument.
With no filename supplied it will use a default name based on the
current time.

The default file will get the extension `png` for screenshots and `webm`
for video capture.

1 files changed, 23 insertions, 4 deletions

diff --git a/swaygrab/main.c b/swaygrab/main.c
index 671b8737..1120f0d5 100644
--- a/swaygrab/main.c
+++ b/swaygrab/main.c
@@ -135,6 +135,19 @@ char *get_focused_output(int socketfd) {
         return output;
 }
 
+char *default_filename(const char *extension) {
+        int ext_len = strlen(extension);
+        int len = 28 + ext_len; // format: "2015-12-17-180040_swaygrab.ext"
+        char *filename = malloc(len * sizeof(char));
+        time_t t = time(NULL);
+
+        struct tm *lt = localtime(&t);
+        strftime(filename, len, "%Y-%m-%d-%H%M%S_swaygrab.", lt);
+        strncat(filename, extension, ext_len);
+
+        return filename;
+}
+
 int main(int argc, char **argv) {
         static int capture = 0, raw = 0;
         char *socket_path = NULL;
@@ -214,10 +227,7 @@ int main(int argc, char **argv) {
                 if (optind >= argc + 1) {
                         sway_abort("Invalid usage. See `man swaygrab` %d %d", argc, optind);
                 }
-        } else {
-                if (optind >= argc) {
-                        sway_abort("Invalid usage. See `man swaygrab`");
-                }
+        } else if (optind < argc) {
                 file = argv[optind];
         }
 
@@ -228,6 +238,14 @@ int main(int argc, char **argv) {
                 output = get_focused_output(socketfd);
         }
 
+        if (!file) {
+                if (!capture) {
+                        file = default_filename("png");
+                } else {
+                        file = default_filename("webm");
+                }
+        }
+
         if (!capture) {
                 grab_and_apply_magick(file, output, socketfd, raw);
         } else {
@@ -235,6 +253,7 @@ int main(int argc, char **argv) {
         }
 
         free(output);
+        free(file);
         close(socketfd);
         return 0;
 }