From 42ee9e7c8560ebdc9ef79c46a1b0f3ffb33eb926 Mon Sep 17 00:00:00 2001
From: Sean Whitton <spwhitton@spwhitton.name>
Date: Sun, 25 Sep 2022 22:34:09 -0700
Subject: add --socket-name support to emacsclient(1) wrapper

---
 bin/emacsclient | 50 +++++++++++++++++++++++++++++++-------------------
 1 file changed, 31 insertions(+), 19 deletions(-)

(limited to 'bin/emacsclient')

diff --git a/bin/emacsclient b/bin/emacsclient
index e11cbe9c..0e6ab7a6 100755
--- a/bin/emacsclient
+++ b/bin/emacsclient
@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 
 # Copyright (C) 2022  Sean Whitton
 #
@@ -20,25 +20,38 @@
 # emacsclient(1) wrapper to handle updating the environment of existing
 # daemons and choosing between installed and in-tree builds of Emacs.
 
+min_arg=0
+
 for arg do
     shift
     case "$arg" in
 	'--spw/installed') mode=--spw/installed ;;
 	'--spw/update-environment') update=true ;;
+	'-s'|'--socket-name') min_arg=2; daemon_name="$1"        ;;&
+	'-s'?*)               min_arg=1; daemon_name="${arg:2}"  ;;&
+	'--socket-name='?*)   min_arg=1; daemon_name="${arg:14}" ;;&
 	*) set -- "$@" "$arg" ;;
     esac
 done
 
-processes=$(ps -o exe -u "$LOGNAME" -U "$LOGNAME")
-echo "$processes" | grep -q "$HOME/src/emacs/src/emacs" && devel_running=true
-echo "$processes" | grep -q $(command -v emacs) && installed_running=true
+command -v ss >/dev/null || exit 1
+socket="/run/user/$(id -u)/emacs/${daemon_name:-server}"
+listener="$(ss -Hplx src $socket | perl -wne'/pid=(\d+)/ and print $1')"
+
+if [ -z "$listener" -a -e "$socket" ]; then
+    # Nothing is listening: remove dangling socket.
+    rm "$socket"
+elif [ -n "$listener" ]; then
+    case "$(ps h -o exe $listener | sed -e 's/ (deleted)$//')" in
+	"$HOME/src/emacs/src/emacs")       devel_running=true     ;;
+	"$(realpath $(command -v emacs))") installed_running=true ;;
+	*) echo >&2 "Unknown Emacs listening on $socket"; exit 1  ;;
+    esac
+fi
 
 if [ "$devel_running" = true -a "$mode" = --spw/installed ]; then
-    pgrep --full "$HOME/src/emacs/src/emacs" | while read pid; do
-	kill $pid
-    done
-    socket="/run/user/$(id -u)/emacs/server"
-    [ -e $socket ] && inotifywait -qqt 2 -e delete $socket
+    kill "$listener"
+    [ -e "$socket" ] && inotifywait -qqt 2 -e delete "$socket"
     devel_running=false
 fi
 
@@ -65,9 +78,7 @@ fi
 # allows us to have the Emacs daemon survive restarts of the graphical desktop
 # environment, and to update Emacs on a remote host when there is a new
 # forwarded SSH agent socket.  See 'upenv' in .bash_defns.
-if [ "$update" = true \
-	       -a \( "$devel_running" = true \
-	             -o "$installed_running" = true \) ]; then
+if [ "$update" = true -a -n "$listener" ]; then
     for var in DISPLAY WAYLAND_DISPLAY \
 		       XAUTHORITY WINDOWID \
 		       XDG_SESSION_TYPE XDG_CURRENT_DESKTOP \
@@ -81,15 +92,16 @@ if [ "$update" = true \
 	fi
     done
     [ -n "$args" ] \
-	&& "$emacsclient" --eval "(spw/update-environment$args))"
+	&& "$emacsclient" -s"${daemon_name:-server}" \
+			  --eval "(spw/update-environment$args))"
 fi
 
 # emacsclient(1) requires an argument.  As a special case, if there are no
-# arguments and no daemon is running, just start one.  And if there were no
-# arguments but we were requested just to update env vars, exit peacefully.
-if [ "$#" -eq 0 \
-	  -a "$devel_running" != true -a "$installed_running" != true ]; then
-    exec "$emacs" --daemon
-elif ! [ "$#" -eq 0 -a "$update" = true ]; then
+# arguments except -s/--socket-name, and no daemon is running, just start one.
+# And if there were no arguments but we were requested just to update env
+# vars, exit peacefully.
+if [ "$#" -eq "$min_arg" -a -z "$listener" ]; then
+    exec "$emacs" --daemon"${daemon_name:+=$daemon_name}"
+elif ! [ "$#" -eq "$min_arg" -a "$update" = true ]; then
     exec "$emacsclient" -a "" "$@"
 fi
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