diff --git a/README.md b/README.md
index f59a197..ca3a4ad 100644
--- a/README.md
+++ b/README.md
@@ -34,7 +34,8 @@ Updating only a single file? Use SyndiShanX's online tool instead: https://syndi
     - See section below for detailed info
 3. Run the script
     - `cd ./ClassUpdate`
-    - `python ./replace.py`
+    - `python ./replace.py [config_profile|theme_dir]`
+> use `-help` to see flags
 
 ### Example
 Files marked with `↻` will be updated by the script if using the default config.
diff --git a/lib/input.py b/lib/input.py
index 2e64b94..c3f3638 100644
--- a/lib/input.py
+++ b/lib/input.py
@@ -5,10 +5,28 @@
 import configparser
 import glob
 import os.path
+import sys
 
 from lib.format import ind, q
 
+flags, args = {}, []
+for s in sys.argv[1:]:
+    if s.startswith('-'):  # format to {key:value} from -key=value
+        flag = s.split('=')
+        flags[flag[0][1:]] = flag[1] if len(flag) > 1 else None
+    else:
+        args.append(s)
+
+if 'h' in flags or 'help' in flags:
+    print("""usage: <dir|profile> [flags]
+flags:
+    -y: skip confirmation dialog
+    -x=<value>, -ext=<value>: file extension to filter for
+    -diff=<dir|url>: diff source to use""")
+    sys.exit()
+
 __all__ = ["get_params"]
+__root__ = os.path.dirname(os.path.dirname(__file__))
 
 
 def try_user(config, profile):
@@ -24,16 +42,43 @@ def try_user(config, profile):
 def get_config(config_filename):
     """Get parameters from config file."""
     raw_config = configparser.ConfigParser()
+
+    config_filename = os.path.join(__root__, config_filename)
     if not os.path.exists(config_filename):
         raise FileNotFoundError("Config file not found.")
     raw_config.read(config_filename)
 
     profile = "DEFAULT"
-    if input(f"Use {q(profile)} profile? [Y/n]\t").lower() == "n":
+    is_path = False
+    if len(args) != 0:
+        is_path = os.path.isdir(args[0])
+
+        if not is_path:
+            profile = args[0]
+    elif input(f"Use {q(profile)} profile? [Y/n]\t").lower() == "n":
         profile = input("Config profile name:\t\t")
         profile = try_user(raw_config, profile)
 
-    config_user = raw_config[profile]
+    if profile in raw_config:
+        config_user = raw_config[profile]
+    else:
+        raise ValueError(f'unknown profile/directory: "{profile}"')
+
+    if is_path:
+        config_user["ThemeDirectory"] = os.path.abspath(args[0])
+    else:
+        # backwards compat.
+        config_user["ThemeDirectory"] = os.path.abspath(__root__+'/../'+config_user["ThemeDirectory"])
+
+    if "ext" in flags:
+        config_user["FileExtension"] = flags["ext"]
+    elif "x" in flags:
+        config_user["FileExtension"] = flags["x"]
+
+    if "diff" in flags:
+        config_user["DiffLocation"] = flags["diff"]
+        config_user["UseLocalDiff"] = "no" if flags["diff"].startswith("http") else "yes"
+
     config = {
         "dir": config_user["ThemeDirectory"],
         "ext": config_user["FileExtension"],
@@ -41,6 +86,8 @@ def get_config(config_filename):
         "location": config_user["DiffLocation"],
     }
 
+    if config["uselocaldiff"] and not os.path.exists(config["location"]):
+        raise FileNotFoundError("Diff file not found.")
     return config
 
 
@@ -53,10 +100,11 @@ def get_params():
     print(ind(f"Diff file location:\t{config['location']}"))
 
     filenames = glob.glob(os.path.join(
-        "..", config["dir"], "**", "*." + config["ext"]
+        config["dir"], "**", "*." + config["ext"]
     ), recursive=True)
 
     print(f"\nFound {len(filenames)} {config['ext']} files in {config['dir']}.")
-    input("Press enter to continue or Ctrl+C to cancel.")
+    if 'y' not in flags:
+        input("Press enter to continue or Ctrl+C to cancel.")
 
     return config["uselocaldiff"], config['location'], filenames