sst: Reliable SSH connections using tmux

sst

#!/bin/sh

# SST: SSH, but reliable, using tmux.
# When you lose connection, the connection will be re-tried, and you will get back where you
# left off.
# An aggressive heartbeat setting is used to detect network issues much more reliably than
# SSH's default settings would.
# 
# Usage:
#   sst <host>:           Create a temporary tmux session, which will be killed when it hasn't
#                         been used in a while
#   sst <host> <session>: Connect to an existing tmux session

if [ -z "$1" ]; then
	echo "Usage: $0 <server> [tmux session]"
fi

server="$1"
if [ -n "$2" ]; then
	tmux="$2"
	temporary=0
else
	id="sstemp-$RANDOM"
	tmux="$id"
	temporary=1
fi

if [ "$temporary" = 1 ]; then
	tempfile="/tmp/$USER-$id"
	cmd="([ -n \"\$BASH_VERSION\" ] && shopt -s huponexit); "
	cmd="${cmd}([ ! -e $tempfile ] && nohup >$tempfile.nohup 2>&1 sh -c \"while :; do sleep 100; if ! [ -e $tempfile ]; then tmux kill-session -t $tmux; break; fi; rm -f $tempfile; done\") & "
	cmd="${cmd}if [ -e $tempfile ]; then NEWSESSION=0; else NEWSESSION=1; fi; "
	cmd="${cmd}(while :; do touch $tempfile; sleep 10; done) & "
	cmd="${cmd}if [ \$NEWSESSION = 0 ]; then tmux attach -t $tmux; else tmux new -s $tmux; fi"
else
	cmd="tmux attach -t $tmux"
fi

while :; do
	ssh -t -o 'ServerAliveInterval 2' -o 'ServerAliveCountMax 2' "$server" "$cmd" && break
	sleep 2
done