Added some docs

docs/src/distributed.rst

@@ -141,7 +141,12 @@ client becomes a significant overhead for the calculation. UNIX-domain
 sockets create a special file in the local file system, that serves as a
 rendezvous point between server and clients, and are uniquely identified
 by the name of the file itself, that can be specified in the “address”
-tag of in the xml input file and in the input of the client.
+tag of in the xml input file and in the input of the client. By default
+this file is created based on the address tag, with a `/tmp/ipi_` prefix.
+This can be overridden setting the “sockets_prefix” attribute for the
+:ref:`simulation` tag in the input file, or on the command-line using the
+`-S` option. Note that several clients do not support changing the default
+prefix.
 
 Unfortunately, UNIX sockets do not allow one to run i-PI and the clients
 on different computers, which limits greatly their utility when one

ipi/inputs/simulation.py

@@ -147,7 +147,7 @@ class InputSimulation(Input):
             {
                 "dtype": str,
                 "default": "/tmp/ipi_",
-                "help": "A prefix prepended to all Unix-domain sockets.",
+                "help": "A prefix prepended to the `address` value to form the UNIX-domain socket location.",
             },
         ),
     }

ipi/utils/inputvalue.py

@@ -829,12 +829,15 @@ def help_rst(self, name="", indent="", level=0, stop_level=None, standalone=True
             # For classes such as InputCell, self._default is not the value,
             # instead it is an object that is stored, putting the default value in
             # self.value. For this reason we print out self.value at this stage,
-            # and not self._default
+            # and not self._default. We also escape underscores that might appear
+            # in the default string value.
             rstr += (
                 "\n"
                 + indent
                 + "*default*: "
-                + self.pprint(self.value, indent=indent, latex=False)
+                + self.pprint(self.value, indent=indent, latex=False).replace(
+                    "_", r"\_"
+                )
                 + "\n"
             )