swap_link first working version

swap_link.py

@@ -0,0 +1,32 @@
+# swap_link.py
+# Replace a link file with another one pointing to a new target
+#
+
+from pathlib import Path
+from os.path import relpath # won't be necessary with Python 3.12 thanks to walk_up arg in relative_to()
+
+def swap_link(lnk, tgt):
+    #lnk: symbolic link to swap
+    #tgt: target for new link
+    lnpath = Path(lnk)
+    if not lnpath.is_symlink():
+        raise Exception("First argument is not a symbolic link")
+    elif lnpath.exists():
+        raise Exception("Link is not broken")
+
+    tpath = Path(tgt)
+    if tpath.is_symlink():
+        if not tpath.exists():
+            raise Exception("Target is also a broken link!")
+        elif tpath.readlink().resolve() == lnpath.resolve() :
+            raise Exception("Target is a link to link to be fixed...")
+    
+    try:
+        lnpath.unlink()
+    except Exception(e):
+        raise Exception("Failed to unlink lnk. Check permissions!")
+
+    lnpath = Path(lnk)
+
+    sym_path = relpath(tgt, lnk)[3:]
+    lnpath.symlink_to(sym_path)