diff --git a/glsl2c.py b/glsl2c.py
index ed8cde5..ac52017 100644
--- a/glsl2c.py
+++ b/glsl2c.py
@@ -1,35 +1,46 @@
 #!/usr/bin/env python3
+
 import sys
 from pathlib import Path
 
-src = sys.argv[1]
-dst = sys.argv[2]
+line: int = 12
 
-if len(sys.argv) != 3 or not src.endswith((".glsl", ".vert", ".frag")):
-    sys.exit(1)
-
-# variable name
-varname = src.replace("/", "_").replace(".", "_")
-
-# read to binary mode
-content = Path(src).read_bytes()
-
-line = 12
-
-with open(dst, "w") as f:
-    # content array
-    f.write(f"unsigned char {varname}[] = {{\n")
-    
+def write_binary(content: str) -> str:
+    text = ""
     for i, byte in enumerate(content):
-        # tab
         if i % line == 0:
-            f.write("\t")
-        # hexa
-        f.write(f"0x{byte:02x}, ")
-        
-        # LF/CRLF
+            text += "\t"
+        text += f"0x{byte:02x}, "
         if (i + 1) % line == 0:
-            f.write("\n")
-    f.write("};\n")
-    # content size
-    f.write(f"unsigned int {varname}_len = {len(content)};")
\ No newline at end of file
+            text += "\n"
+    text += "\n"
+    return text
+
+def main() -> int:
+    # check arguments
+    if len(sys.argv) < 2 or len(sys.argv) > 3:
+        print("glsl2c.py <shader_file> [output_c_file]")
+        return 1
+
+    src = Path(sys.argv[1])
+
+    if not src.suffix.endswith((".glsl", ".frag", ".vert")):
+        print(f"file error: cannot convert {src.suffix} to .c file")
+        return 1
+
+    dst = Path(sys.argv[2]) if len(sys.argv) == 3 else src.with_suffix(".c")
+
+    # variable name
+    varname = f"{src.stem}_{src.suffix[1:]}"
+
+    # read binary
+    content = src.read_bytes()
+
+    with open(dst, "w") as f:
+        f.write(f"unsigned char {varname}[] = {{\n{write_binary(content)}}};\n")
+        f.write(f"unsigned int {varname}_len = {len(content)};\n")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())