Replace Bash swapfile script with Python implementation using argparse

- Added btrfs-safe handling (/var/swap/swapfile)
- Automatically recreates swapfile if size differs
- Removed legacy main.sh
Conversation: https://chatgpt.com/share/68d2c38b-84dc-800f-9ca4-dffa158c8e80

main.py

@@ -0,0 +1,113 @@
+#!/usr/bin/env python3
+import argparse
+import os
+import re
+import shutil
+import subprocess
+from pathlib import Path
+
+FSTAB_FILE = Path("/etc/fstab")
+BTRFS_SWAP_DIR = Path("/var/swap")
+BTRFS_SWAP_PATH = BTRFS_SWAP_DIR / "swapfile"
+DEFAULT_SWAP_PATH = Path("/swapfile")
+
+
+def run(cmd, check=True, capture=False):
+    """Helper to run shell commands."""
+    kwargs = {"check": check}
+    if capture:
+        kwargs["stdout"] = subprocess.PIPE
+        kwargs["stderr"] = subprocess.PIPE
+        kwargs["text"] = True
+    return subprocess.run(cmd, **kwargs)
+
+
+def detect_root_fs() -> str:
+    result = run(["findmnt", "-no", "FSTYPE", "/"], capture=True)
+    return result.stdout.strip()
+
+
+def parse_size_to_mib(size: str) -> int:
+    """Convert '64G' or '2048M' into MiB integer."""
+    match = re.match(r"^(\d+)([gGmM]?[bB]?)?$", size.strip())
+    if not match:
+        raise ValueError(f"Invalid size format: {size}")
+    num, unit = match.groups()
+    num = int(num)
+    unit = (unit or "M").lower()
+
+    if unit in ("g", "gb"):
+        return num * 1024
+    elif unit in ("m", "mb"):
+        return num
+    else:
+        raise ValueError(f"Unsupported unit: {unit}")
+
+
+def get_swap_size(path: Path) -> int:
+    """Return swapfile size in MiB if it exists, else 0."""
+    if not path.exists():
+        return 0
+    return path.stat().st_size // (1024 * 1024)
+
+
+def remove_swap(path: Path):
+    """Disable and remove swapfile and its fstab entry."""
+    run(["swapoff", str(path)], check=False)
+    if path.exists():
+        path.unlink()
+    # remove old fstab line
+    if FSTAB_FILE.exists():
+        text = FSTAB_FILE.read_text().splitlines()
+        new_lines = [
+            line for line in text
+            if not re.search(rf"^{re.escape(str(path))}\s+none\s+swap", line)
+        ]
+        FSTAB_FILE.write_text("\n".join(new_lines) + "\n")
+
+
+def create_swap(path: Path, size_mib: int, fs: str):
+    if fs == "btrfs":
+        print(f"Creating {size_mib} MiB swapfile on btrfs at {path}")
+        path.parent.mkdir(parents=True, exist_ok=True)
+        run(["chattr", "+C", str(path.parent)], check=False)
+        run(["btrfs", "property", "set", "-ts", str(path.parent), "compression", "none"], check=False)
+        run([
+            "dd", "if=/dev/zero", f"of={path}", "bs=1M",
+            f"count={size_mib}", "status=progress"
+        ])
+    else:
+        print(f"Creating {size_mib} MiB swapfile on {fs} at {path}")
+        run(["fallocate", "-l", f"{size_mib}M", str(path)])
+
+    run(["chmod", "600", str(path)])
+    run(["mkswap", str(path)])
+    run(["swapon", str(path)])
+    with FSTAB_FILE.open("a") as f:
+        f.write(f"{path} none swap sw 0 0\n")
+
+
+def main():
+    parser = argparse.ArgumentParser(description="SwapForge Python edition")
+    parser.add_argument("size", help="Swapfile size (e.g. 2048M or 64G)")
+    args = parser.parse_args()
+
+    fs = detect_root_fs()
+    path = BTRFS_SWAP_PATH if fs == "btrfs" else DEFAULT_SWAP_PATH
+    new_size = parse_size_to_mib(args.size)
+
+    old_size = get_swap_size(path)
+    if old_size == new_size and old_size > 0:
+        print(f"Swapfile {path} already exists with correct size ({old_size} MiB). Skipping.")
+        return
+
+    if old_size > 0 and old_size != new_size:
+        print(f"Existing swapfile {path} has size {old_size} MiB, expected {new_size} MiB. Recreating...")
+        remove_swap(path)
+
+    create_swap(path, new_size, fs)
+    print("Done.")
+
+
+if __name__ == "__main__":
+    main()

main.sh

@@ -1,14 +0,0 @@
-#!/bin/bash
-FSTAB_SWAP_ENTRY="/swapfile none swap defaults 0 0"
-SWAP_FILE="/swapfile"
-FSTAB_FILE="/etc/fstab"
-if grep -q "$FSTAB_SWAP_ENTRY" "$FSTAB_FILE"; then
-	echo "Skipping creation of swap partion because entry allready exists in \"$FSTAB_FILE\"!"
-else
-	echo "Creating swap partition..." &&
-	sudo fallocate -l "$1" "$SWAP_FILE" &&
-	sudo chmod 600 "$SWAP_FILE" &&
-	sudo mkswap "$SWAP_FILE" &&
-	sudo swapon "$SWAP_FILE" &&
-	sudo sh -c "echo \"$FSTAB_SWAP_ENTRY\">>\"$FSTAB_FILE\"" || exit 1
-fi