findsock

tiny/GNUmakefile

@@ -17,6 +17,7 @@ install: \
 	$(BINDIR)/psg \
 	$(BINDIR)/save \
 	$(BINDIR)/savedate \
+	$(BINDIR)/findsock \
 
 fnp: fnp.sh
 fnpa: fnpa.sh

tiny/findsock

@@ -0,0 +1,19 @@
+#!/bin/sh
+#
+# Stupid little program to find the socket of stdin of the parent
+# of the specified process. Normally this is used for the 
+# login shell to determine to which of several virtual hosts the
+# user connected.
+
+if [ $# -eq 0 ]
+then
+	echo "Usage: $0 <pid of login shell>" >&2
+	exit 1
+fi
+
+pid=$1
+
+ppid=`ps -ef | awk -v pid=$pid '$2 == pid { print $3 }'`
+
+sock=`lsof -p $ppid 2>/dev/null | awk '$4 == "0u" && $5 == "inet" { print $9 }'`
+echo $sock