Rediscovering screen and discovering tmux
“Day 9: A long relationship with text terminals”
I never used a VT52, but I did use VT52 compatible terminals, and I used genuine VT100s. Later I used VT220s. At university these were connected onto VAXen either directly or via Gandalf switches, then once I started work they hung off GEC4000 series machines. Later we would put SPIF boards onto our Sun boxes (Serial and Parallel InterFace) and for some years I worked at a desk with a VT220 directly onto a Sun box.
This was when I first used GNU Screen. On the big screens on the Sun workstations there was a window manager running, so you would have multiple windows open for your different working contexts. On a terminal I used GNU Emacs as a quasi window system – buffers for editing source files, buffers for running make, or running grep, or running a shell. Hell, for years I used Emacs RMail mode as my email client.
But tools were moving on. My email was on a remote IMAP server, and I defected to PINE. And my colleague introduced me to GNU Screen – a session manager for terminal windows. Its USP for me was the ability to run multiple sessions on a single terminal and switch between them using a Control sequence (as an Emacs user I quickly changed the escape character from Ctrl-a to Ctrl-z).
I hadn't thought about GNU Screen for years and years until today. Almost everything we do lives in its own window, and you can start another context at the click of a mouse. At times you will end up with many PuTTY windows open, and have to do beat them into submission, but that's just how it is. Then I was watching a video signposted by Kev Quirk about git (which I strongly recommend – you'll learn what git does and then how to use it). The instructor was moving freely between contexts in a full screen terminal session, and it turns out that not only is Screen still a thing, there is a new emulator “tmux”.
This is day one of using tmux. It solves a specific annoyance: having multiple PuTTY windows open onto the same host for different purposes, and finding you're in the wrong context. So, for example, you can have a window as your regular user and another windows as root. You can have a window open in the config file directory where you're hacking, and another window open in the logfile directory. But tmux goes further than that: you can divide the window into panes, so you can have a pane running “tail -f .log” while you restart a service in another pane. All within the same PuTTY session. And tmux retains the ability of Screen to detach and reattach a session: apart from anything else, this means that if your connection gets dropped for some reason you haven't lost your context.
I'll need some weeks of usage to settle into my modus operandi with tmux, but it's clear that from now my UserData for new instances is going to include “yum install -y tmux” immediately after “yum install -y emacs”.