add utilities for running commands and folder permission checking

nslsii/utils.py

@@ -0,0 +1,40 @@
+import os
+import re
+import subprocess
+
+
+def run(cmd, path="", ignoreErrors=True, returnError=False, debug=False):
+    """cmd should be a list, e.g. ["ls", "-lh"]
+    path is for the cmd, not the same as cwd
+    """
+    cmd[0] = path + cmd[0]
+    p = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+    out, err = p.communicate()
+    if debug:
+        print(out.decode(), err.decode())
+    if len(err) > 0 and not ignoreErrors:
+        print(err.decode())
+        raise Exception(err.decode())
+    if returnError:
+        return out.decode(), err.decode()
+    else:
+        return out.decode()
+
+
+def check_access(fn):
+    if not os.path.exists(fn):
+        raise Exception(f"{fn} does not exist ...")
+    if os.access(fn, os.W_OK):
+        print(f"write access to {fn} verified ...")
+        return
+
+    # this below may not be necessary
+    out = run(["getfacl", "-cn", fn])
+    wgrps = [int(t[:-4].lstrip("group:")) for t in re.findall("groups:[0-9]*:rw.", out)]
+    ugrps = os.getgroups()
+    if len(set(wgrps) & set(ugrps)) == 0:
+        print("groups with write permission: ", wgrps)
+        print("user group membership: ", ugrps)
+        raise Exception(f"the current user does not have write access to {fn}")
+    else:
+        print(f"write access to {fn} verified ...")