fixed block on stdin empty

meme_otron/__main__.py

@@ -41,7 +41,7 @@ if __name__ == "__main__":
             except IOError as e:
                 print(f"Cannot read '{input_file}': {e}", file=sys.stderr)
                 sys.exit(1)
-        elif not sys.stdin.isatty():
+        elif utils.is_stdin_ready():
             input_data = utils.read_stream(sys.stdin.buffer)
 
         img, errors = meme_otron.compute(*sys.argv[1:], input_data=input_data, wmark=wmark, debug=debug)

meme_otron/utils.py

@@ -1,4 +1,5 @@
 import re
+import select
 import sys
 from urllib.request import urlopen
 from urllib.error import URLError
@@ -220,6 +221,13 @@ def safe_index(src: Union[str, list], pattern, start: int = 0):
 # region bytes utils
 
 
+def is_stdin_ready() -> bool:
+    """
+    https://stackoverflow.com/questions/3762881/how-do-i-check-if-stdin-has-some-data
+    """
+    return sys.stdin.isatty() and select.select([sys.stdin, ], [], [], 0.0)[0]
+
+
 def read_stream(stream: BinaryIO) -> bytes:
     output_data = bytearray()
     for line in stream: