with-editor-sleeping-editor: document csh complications

Closes #9.

1 files changed, 20 insertions, 1 deletions

diff --git a/with-editor.org b/with-editor.org
index edf0134..7fb73fc 100644
--- a/with-editor.org
+++ b/with-editor.org
@@ -127,7 +127,26 @@ it receives a signal.
   not a complete substitute for a proper Emacsclient, it can only
   be used as ~$EDITOR~ of child process of the current Emacs instance.
 
-  It is unlikely that you should ever have to customize this option.
+  Some shells do not execute traps immediately when waiting for a
+  child process, but by default we do use such a blocking child
+  process.
+
+  If you use such a shell (e.g. ~csh~ on FreeBSD, but not Debian), then
+  you have to edit this option.  You can either replace ~sh~ with ~bash~
+  (and install that), or you can use the older, less performant
+  implementation:
+
+  #+BEGIN_SRC emacs-lisp
+    "sh -c '\
+    echo \"WITH-EDITOR: $$ OPEN $0\"; \
+    trap \"exit 0\" USR1; \
+    trap \"exit 1\" USR2; \
+    while true; do sleep 1; done'"
+  #+END_SRC
+
+  This leads to a delay of up to a second.  The delay can be shortened
+  by replacing ~sleep 1~ with ~sleep 0.01~, or if your implementation does
+  not support floats, then by using ~nanosleep 0.01~ instead.
 
 ** Using With-Editor commands