No one told me about this!

[brownbetty]

pixel's post below reminded me that I have meant to post this for a while: Screen! Screen seems sort of like the secret weapon of command-line users; somehow it takes one ages to discover it, and if one is not far enough along in one's command-line usage, it just ends up seeming sort of mean-spirited and baffling. It's documented, but it's such a swiss-army knife that it's easy to get lost in the maze of documentation. However, at a certain level of usage, it suddenly becomes the most useful program ever.

So I wanted to ask people their favourite things to do with screen, and to share their .screenrc files, where they've modified them in interesting ways.

I still remember that happy day when I discovered that screen could monitor a background window, and tell me when it changed or stopped changing. The latter was the revolutionary one, for me; I could start something enormous compiling, and then neglect it, secure in the conviction screen would let me know when it finished. If your keybindings are standard, "ctrl-a, _" will monitor for silence, and "ctrl-a, m" will monitor for change/movement.

My screenrc is very lightly customized, a relic of my old machine which would barf and die if asked to update screen too often, but I like it. The interesting entry is

caption always "%{= kw} %-Lw [%n-%f %t] %+Lw %?@%u%?%? [%h]%?"

This gives me a strip at the bottom of the session which lists my windows by name and number, ferrinstance, at this moment:

[0-$ bash]   1$ newsbeuter  2-$ mutt  3$ rtorrent 

where the active window is in square brackets. Mutt has a hyphen after the window because it's the last active window, and the one I'd go to if I used "ctrl-a a" to return to my previous. If one of my windows had produced an alert, I'd get a "!".

You can do some really crazy stuff with the caption command, although the syntax is so arcane it requires years of study. I'm pretty sure most people copy someone else's and fiddle with it to get what they want, rather than attempt to write one from scrap.

Comments

[kerravonsen]

Nifty thing to do with screen: controlling curses apps.
I use "randomplay" to play music (randomly, naturally). Unfortunately, it isn't one of those command-line apps where you can send commands to the daemon by typing a new command. It's a curses app, where you type commands in the terminal it's running in. However, I discovered a little-known thing about screen: one can pipe characters to its command buffer. Which means that one can write a script to send commands to a curses app which is running inside screen. Which means that one can use something like "xbindkeys" to bind a function key to call a script to send commands to a curses app running in screen! Yes, it all sounds a bit like "The House that Jack Built", but it means that I can use my nice multimedia keyboard to control my music-playing, rather than having to grovel around with multiple mouse-clicks when I want to pause my music because the phone rings.

This is the screen session for randomplay:

source $HOME/.byobu/profile
sessionname play
screen -t play 1 randomplay

This is the "sendplay" script:

#!/bin/zsh
# send commands to the "play" screen session
COMMAND=$1
shift
CMD_BUFFER=/tmp/screen-exchange
SESS=play
WIND=1

case $COMMAND in
next|fore*)
        echo -n f >$CMD_BUFFER
        ;;
prev|back*)
        echo -n b >$CMD_BUFFER
        ;;
*pause|*play)
        echo -n p >$CMD_BUFFER
        ;;
help)
        echo -n h >$CMD_BUFFER
        ;;
more|plus)
        echo -n + >$CMD_BUFFER
        ;;
less|minus)
        echo -n - >$CMD_BUFFER
        ;;
stop|quit)
        echo -n q >$CMD_BUFFER
        ;;
start)
        screen -d -m -c $HOME/.byobu/play
        exit
esac

screen -S $SESS -X select $WIND
screen -S $SESS -X readbuf
screen -S $SESS -X paste .
screen -S $SESS -X redisplay

And here are the relevant bindings in my .xbindkeysrc:

"sendplay prev; omessage '<< prev'"
  XF86AudioPrev

"sendplay less; omessage 'weight--'"
  Control + XF86AudioPrev

"sendplay next; omessage 'next >>'"
  XF86AudioNext

"sendplay more; omessage 'weight++'"
  Control + XF86AudioNext

"sendplay stop; omessage 'stop |#|'"
  XF86AudioStop

"sendplay toggleplay; omessage 'P/P >||'"
  XF86AudioPlay

"sendplay start; omessage 'play >'"
  Control + XF86AudioPlay

[pixel]

This is very cool. If I used something besides Pandora/Slacker I'd be all over it.

[brownbetty]

This is crazy! I feel like I am only remotely grasping the possibilities.