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📟 Screen – Virtual Terminal Manager

Screen multiplexes a physical terminal between several processes (typically interactive shells). Each virtual terminal emulates a DEC VT100 and provides scrollback history, copy/paste, and detach/reattach capabilities.

🚀 Quick Reference

Use Case	Command / Keystroke	Description
Start a new session	screen	Create a window with a shell
Create a new window	C-a c	Start a new shell window
Detach session	C-a d	Detach and leave processes running
Reattach session	screen -r	Reattach to a detached session
List windows	C-a w	Show all windows with numbers/titles
Select window by number	C-a 0…9	Jump to window n
Next / Previous window	C-a n / C-a p	Cycle through windows
Kill current window	C-a k	Destroy window (and its process)
Split region horizontally	C-a S	Split the display
Split region vertically	C-a |	Vertical split
Enter copy/scrollback mode	C-a [	Copy text from scrollback
Paste buffer	C-a ]	Paste copied text
Lock screen	C-a x	Lock terminal (requires lock program)
Quit screen	C-a \	Kill all windows and exit
Show help (key bindings)	C-a ?	Display all bound commands

📋 Overview

Screen creates a single window with a shell (or a specified command) and gets out of your way. At any time you can create new windows, switch between them, kill windows, view a list, turn on logging, copy/paste text, and detach the whole session. All windows run independently; processes continue even when their window is not visible or when the session is detached.

Everything you type goes to the current window except the command prefix (default C-a). Commands are two strokes: one to initiate, one to act. The command character and all key bindings are fully customisable.

New windows are created with C-a c. You can also launch new windows from a shell inside an existing window: screen emacs prog.c.

If /run/utmp is writable, screen adds entries for each window (useful for talk, shutdown, etc.).

⚙️ Invoking Screen

Command‑line options (abbreviated):

• -a – include all capabilities in window’s termcap (even if redraw needed).
• -A – adapt all window sizes to the display size on attach.
• -c file – use file instead of $HOME/.screenrc.
• -d / -D [pid.sessionname] – detach a session running elsewhere. Combine with -r/-R for powerful reattach.
• -e xy – set command character to x and literal command character to y. Default ^Aa.
• -f / -fn / -fa – flow control: on, off, auto.
• -h num – set scrollback history lines.
• -i – make interrupt key (C-c) interrupt display immediately when flow control is on (discouraged).
• -l / -ln – turn login mode on/off (utmp recording).
• -ls / -list [match] – list session IDs and statuses.
• -L – turn on automatic output logging for windows.
• -Logfile file – set logfile name (default screenlog.0).
• -m – ignore $STY; always create a new session.
• -O – use a more optimal output mode (affects auto‑margin terminals without LP).
• -p name_or_number – preselect a window. Special: - (blank), = (windowlist), + (new).
• -q – suppress error messages; set exit values for -ls / -r.
• -Q – query commands from a remote session (e.g., screen -Q windows).
• -r [pid.sessionname] – resume a detached session.
• -R – reattach if unambiguous, else list sessions.
• -RR – resume most‑recently created detached session, or start new.
• -s program – default shell program.
• -S sessionname – set a name for the session.
• -t name – set title for default shell or specified program.
• -T term – set $TERM value.
• -U – run in UTF‑8 mode.
• -v – print version.
• -wipe [match] – list sessions and remove destroyed ones.
• -x – attach to a session already attached elsewhere (multi‑display mode).
• -X – send a command to a running session.

🔧 Customisation (.screenrc)

Default settings can be modified via a personal .screenrc file and/or /etc/screenrc. Environment variables $SYSSCREENRC, $SCREENRC, and $HOME/.screenrc are searched. Option -c overrides.

📁 Startup Files

Commands are one per line; empty lines ignored. Arguments separated by tabs/spaces, may be quoted. # starts a comment (except in quotes). Variable substitution: $VAR or ${VAR}.

📜 Source

• source file – read and execute commands from a file. Nested up to 10 levels. Note that termcap/terminfo commands only work at startup/reattach time.

📝 Colon (online customisation)

• colon (C-a :) – enter .screenrc commands interactively. Set commands no longer require set; use def… for defaults.

📖 Commands

A command may be bound to a key, used in screenrc, or typed at the colon prompt. All commands can be bound to keys (since v3.3).

🧩 Default Key Bindings

Keystroke	Command	Description
C-a '	select	Prompt for window identifier and switch
C-a "	windowlist -b	Present list of all windows
C-a 0…9, -	select	Switch to window number or blank
C-a Tab	focus	Switch focus to next region
C-a C-a	other	Toggle to previously displayed window
C-a a	meta	Send the command character (C-a) to window
C-a A	title	Enter a title for current window
C-a b, C-b	break	Send a break to the tty
C-a B	pow_break	Close and reopen tty line
C-a c, C-c	screen	Create new window with shell
C-a C	clear	Clear screen
C-a d, C-d	detach	Detach from terminal
C-a D D	pow_detach	Detach and logout
C-a f, C-f	flow	Cycle flow control on/off/auto
C-a F	fit	Resize window to region size
C-a C-g	vbell	Toggle visual bell
C-a h	hardcopy	Write hardcopy to file
C-a H	log	Toggle logging
C-a i, C-i	info	Show info about current window
C-a k, C-k	kill	Destroy current window
C-a l, C-l	redisplay	Refresh current window
C-a L	login	Toggle window’s login state
C-a m, C-m	lastmsg	Repeat last message
C-a M	monitor	Toggle activity monitoring
C-a SPC, n, C-n	next	Switch to next window
C-a N	number	Show current window number / title
C-a p, C-p, C-h, Backspace	prev	Switch to previous window
C-a q, C-q	xon	Send ^Q (XON) to current window
C-a Q	only	Delete all regions but current
C-a r, C-r	wrap	Toggle line‑wrap
C-a s, C-s	xoff	Send ^S (XOFF)
C-a S	split	Split region horizontally
C-a t, C-t	time	Show load average and time
C-a v	version	Display version
C-a C-v	digraph	Enter digraph sequence
C-a w, C-w	windows	List active windows
C-a W	width	Toggle between 80 and 132 columns
C-a x, C-x	lockscreen	Lock terminal
C-a X	remove	Kill current region
C-a z, C-z	suspend	Suspend screen
C-a Z	reset	Reset virtual terminal to power‑on
C-a .	dumptermcap	Write .termcap file
C-a ?	help	Show key bindings
C-a \	quit	Kill all windows and exit
C-a :	colon	Enter command line
C-a [, C-[, ESC	copy	Enter copy/scrollback mode
C-a ], C-]	paste .	Write paste buffer to stdin of current window
C-a {, C-a }	history	Copy/paste previous (command) line
C-a >	writebuf	Write paste buffer to screen‑exchange file
C-a <	readbuf	Read screen‑exchange file into paste buffer
C-a =	removebuf	Delete screen‑exchange file
C-a _	silence	Monitor window for inactivity
C-a |	split -v	Split region vertically
C-a ,	license	Show copyright page
C-a *	displays	Show listing of attached displays

📚 Command Summary

All commands (abridged):

• acladd usernames – allow other users in this session.
• aclchg usernames permbits list – change a user’s permissions.
• acldel username – disallow other user.
• aclgrp usrname [groupname] – inherit permissions from group leader.
• aclumask [users]+/-bits ... – predefine access to new windows.
• activity message – set activity notification message.
• addacl usernames – synonym to acladd.
• allpartial state – set all windows to partial refresh.
• altscreen state – enable “alternate screen” support.
• at [ident][#|*|%] command [args] – execute command at other displays/windows.
• attrcolor attrib [attribute/color-modifier] – map attributes to colors.
• autodetach state – automatically detach session on SIGHUP.
• autonuke state – enable clear screen to discard unwritten output.
• backtick id lifespan autorefresh command [args] – define a command for the backtick string escape.
• bce [state] – change background‑color‑erase.
• bell_msg [message] – set bell notification message.
• bind [-c class] key [command [args]] – bind a command to a key.
• bindkey [opts] [string [cmd args]] – bind a string to a series of keystrokes.
• blanker – activate screen blanker.
• blankerprg – define a blanker program.
• break [duration] – send break signal to current window.
• breaktype [TCSENDBREAK | TCSBRK | TIOCSBRK] – specify how to generate breaks.
• bufferfile [exchange-file] – select screen‑exchange file.
• bumpleft – swap window with previous one on window list.
• bumpright – swap window with next one on window list.
• c1 [state] – change c1 code processing.
• caption mode [string] – change caption mode and string.
• chacl usernames permbits list – synonym to aclchg.
• charset set – change character set slot designation.
• chdir [directory] – change current directory for future windows.
• cjkwidth – treat ambiguous width characters as full/half width.
• clear – clear window screen.
• collapse – reorder window list, removing number gaps.
• colon – enter a screen command.
• command [-c class] – simulate the screen escape key.
• compacthist [state] – select compaction of trailing empty lines.
• console [state] – grab or ungrab console output.
• copy – enter copy mode.
• copy_reg [key] – (removed) use paste instead.
• crlf state – select line break behavior for copying.
• debug state – suppress/allow debugging output.
• … (many more – full list in original manual)

🪟 New Window

📁 Chdir

chdir [directory] – change default directory for new windows. If omitted, $HOME.

🆕 Screen Command

screen [opts] [n] [cmd [args] | //group] – create a new window. Options: -f flow, -fn, -fa, -t title, -l/-ln login, -T term, -a, -h num, -M (monitoring), -L (logging). If //group, creates a container window.

🌍 Setenv

setenv var string – set environment variable for new windows. unsetenv var – unset it.

🐚 Shell

shell command / defshell command – command to create new shell. Overrides $SHELL. shelltitle title – default title for shells.

🖥️ Term

term term – set $TERM for new windows (discouraged for non‑default; use screen -T term instead).

🧩 Window Types

• Normal: shell or command.
• TTY: connected to a serial device (e.g., /dev/ttya). Optional comma‑separated flags: baud rate, cs8/cs7, ixon/-ixon, ixoff/-ixoff, istrip/-istrip.
• Telnet: //telnet host [port]. Flags shown in info: BINARY, ECHO, SGA, TTYPE, NAWS, LFLOW.

🗂️ Window Groups

Create a container with screen //group. Use group [grouptitle] to show/move windows between groups. Combines well with layouts.

🔎 Selecting a Window

⬅️➡️ Next and Previous

next (C-a SPC, n, C-n) – cycle forward. prev (C-a p, C-p, C-h, Backspace) – cycle backward.

🔄 Other Window

other (C-a C-a) – toggle between current and last window.

🎯 Select

select [n|-|.] (C-a N, C-a ') – switch to window number, blank (-), or current (.).

📋 Windowlist

windowlist [-b] [-m] [-g] (C-a ") – interactive list with navigation (j/k, search, etc.). Custom format via string / title.

🔌 Session Management

✂️ Detach

detach (C-a d) – disconnect and put session in background. autodetach state (default on) – auto‑detach on hangup. password [crypted_pw] – set reattach password.

⚡ Power Detach

pow_detach (C-a D D) – detach and SIGHUP parent process. pow_detach_msg [message] – custom message.

🔒 Lock

lockscreen (C-a x) – run a lock program. $LOCKPRG or builtin.

👥 Multiuser Session

(requires compile‑time support) multiuser state – toggle multi‑user mode. Use acladd, aclchg, acldel, aclgrp, displays, umask, wall, writelock, su.

🏷️ Session Name

sessionname [name] – rename session (caution: old name stays in existing shells). Prefer -S option.

💤 Suspend

suspend (C-a z) – put screen in background.

❌ Quit

quit (C-a \) – kill all windows and exit.

📌 Regions

✂️ Split

split [-v] (C-a S, C-a |) – create a new region. Use focus to toggle.

🎯 Focus

focus [ next|prev|up|down|left|right|top|bottom ] (C-a Tab) – move input focus.

👁️ Only

only (C-a Q) – kill all regions but current one.

🗑️ Remove

remove (C-a X) – kill current region.

📏 Resize

resize [opts] [ [+|-]N[%] | = | max | min | _ | 0 ] – grow/shrink region.

📝 Caption

caption always|splitonly [string] – control caption display and content (default %3n %t).

📐 Fit

fit (C-a F) – resize window to region size.

🔳 Focusminsize

focusminsize [ (width|max|_) (height|max|_) ] – enforce minimum region size.

🗃️ Layout

Subcommands: layout new [title], remove, next, prev, select, show, title, number, attach, save, autosave, dump.

⚙️ Window Settings

📛 Naming Windows

title [windowtitle] (C-a A) – set window name. Dynamic titles: set name as search|name and embed null title escape in prompt.

🖥️ Console

console [state] – grab/release console output (needs TIOCCONS).

💀 Kill

kill (C-a k) – destroy window. Caution: rebind if you use Emacs.

🔑 Login

login [state] (C-a L) – toggle utmp entry. deflogin state sets default.

🔒 Mode

defmode mode – octal pty permissions (default 0622 logged, 0600 others).

👀 Monitor

monitor [state] (C-a M) – watch for activity. silence [state|sec] (C-a _) – watch for silence. activity message, bell_msg message customise notifications.

🪟 Windows

windows [string] (C-a w) – list all windows with status markers: * current, - previous, $ logged in, ! bell, @ activity, (L) logging, &/&& shared, Z zombie. Custom format via string escapes.

📊 Hardstatus

hstatus status – set current window’s hardstatus line. defhstatus [status] – default for new windows.

💻 Virtual Terminal

📜 Control Sequences

Full VT100 emulation plus many ANSI/ISO sequences. (See manual for complete table.)

⌨️ Input Translation

Default key mappings for cursor keys, function keys, keypad, etc. (table in original).

🔡 Digraph

digraph [preset [unicode-value]] (C-a C-v) – enter digraph sequences (e.g., a" → ä). Built‑in table for Latin‑1 etc.

🔔 Bell

vbell [state] (C-a C-g) – toggle visual bell. vbell_msg [message], vbellwait sec.

🧹 Clear

clear (C-a C) – clear and save to scrollback.

ℹ️ Info

info (C-a i) – show cursor position, window size, scrollback, flow, wrap, mode flags, charsets, etc. dinfo – show terminal capabilities.

🔄 Redisplay

redisplay (C-a l) – full redraw. partial state – partial refresh on switch. allpartial state – global override. altscreen state – alternate screen support.

↩️ Wrap

wrap [on|off] (C-a r) – toggle line‑wrap. defwrap state.

🔄 Reset

reset (C-a Z) – reset terminal to power‑on values.

📏 Window Size

width [-w|-d] [cols [lines]] (C-a W) – toggle 80/132 columns. height [-w|-d] [lines [cols]] – set height.

🔣 Character Processing

c1 state, gr state, bce state, encoding enc [denc], charset set, utf8 [state], and their def… counterparts. cjkwidth [state].

📋 Copy and Paste

📑 Copy

copy (C-a [) – enter copy/scrollback mode with vi‑like keys. Features: mark, repeat, search (/, ?, C-s, C-r), yank, append, rectangular blocks. ignorecase [on|off].

📥 Paste

paste [registers [destination]] (C-a ]) – paste from registers/paste buffer. stuff [string] – insert string directly.

💾 Registers

register [-e encoding] key string, readreg [-e encoding] [register [filename]], process [key].

📬 Screen Exchange

bufferfile [exchange-file], readbuf (C-a <), writebuf (C-a >), removebuf (C-a =).

🕰️ History

history (C-a {, C-a }}) – recall command lines based on first letter.

🚀 Subprocess Execution

exec [[fdpat] newcommand [args ...]] – run a filter in the current window. Abbreviations: ! for exec, | for !..|. Examples: /bin/sh, |less, !:sed -n s/.*Error.*/\007/p.

⌨️ Key Binding

bind [-c class] key [command [args]] – define or remove a binding. bindkey for input translation tables. escape xy / defescape xy – set command character. meta (C-a a) – send literal command char. command [-c class] – simulate escape key. help (C-a ?) – show bindings.

🌊 Flow Control

flow [fstate] (C-a f) – on/off/auto. defflow for default. xon (C-a q) / xoff (C-a s) – send ^Q/^S directly. interrupt option flushes output on interrupt.

🧾 Termcap

Windows get screen termcap; can be tweaked. dumptermcap writes a .termcap file. Commands: termcap, terminfo, termcapinfo. Special capabilities: LP, Z0/Z1, WS, NF, G0, etc. Autonuke (autonuke), output buffer limit (obuflimit), character translation (XC).

💬 Message Line

Non‑status terminals: last line used. ANSI Privacy Message can display text. hardstatus configures hardware status line. lastmsg (C-a m) repeats last message. msgminwait, msgwait control timing.

📝 Logging

hardcopy [-h] [file] (C-a h) – dump screen image. log [state] (C-a H) – log window output to screenlog.N. logfile, logtstamp, hardcopydir.

🏁 Startup

echo [-n] message, sleep num, startup_message state – control .screenrc startup.

🧩 Miscellaneous

at, break, pow_break, breaktype, defbreaktype, bumpleft, bumpright, collapse, debug, license, nethack, nonblock, defnonblock, number, time, verbose, version, zombie, zombie_timeout, printcmd, rendition, sorendition, attrcolor, setsid, eval, maxwin, backtick, idle, blanker, blankerprg, zmodem, mousetrack.

🔣 String Escapes

Format strings for captions, hardstatus, windowlist, etc. Escapes: %n (window number), %t (title), %f (flags), %w (window list), %h (hardstatus), %c/%C (time), %H (host), %l (load), %S (session), %{…} (attributes/colors), %?…%:…%? (conditional), %=, %> (truncation/padding), %` (backtick output).

🌍 Environment Variables

COLUMNS, LINES HOME LOCKPRG NETHACKOPTIONS PATH SCREENCAP SCREENDIR SCREENRC SHELL STY SYSSCREENRC TERM TERMCAP WINDOW

📁 Files Referenced

$SYSSCREENRC, /etc/screenrc
$SCREENRC, $HOME/.screenrc
$SCREENDIR/S-<login>
/run/screen/S-<login>
/tmp/screens/screen-exchange
screenlog.[0-9]
hardcopy.[0-9]
.termcap
/usr/lib/terminfo/?/*, /etc/termcap
/run/utmp

🙏 Credits

Originally by Oliver Laumann; maintained by Juergen Weigert, Michael Schroeder, Micah Cowan, Sadrul Habib Chowdhury; since 2015 by Amadeusz Slawinski & Alexander Naumov. Many contributors.

🐛 Bugs

• dm / xs ignored; xn treated as magic margin.
• No double‑high/wide characters support.
• Cannot change $TERMCAP on reattach with different terminal.
• Limited terminfo support.
• No hardware tabs.
• Must be setuid‑root on many systems.
• Utmp entries not removed on SIGKILL.
• Warning when tty has no utmp entry.
• May not auto‑detach on modem hangup unless HUP received.
• Password doesn’t protect -d/-D.
• breaktype affects all windows, not just current.
• Attaching multiuser doesn’t source .screenrc.
• Weird imagination most useful…

Report bugs to screen-devel AT gnu.org. Recompile with -DDEBUG for debug output.

📦 Installation

Requires pseudo‑ttys, select, Unix‑domain sockets. Run ./configure then make. Socket directory defaults to $HOME/.screen or /run/screen.

See INSTALLATION file in distribution.

📟 Screen – Virtual Terminal Manager 🚀 Quick Reference 📋 Overview ⚙️ Invoking Screen 🔧 Customisation (.screenrc) 📖 Commands 🪟 New Window 🔎 Selecting a Window 🔌 Session Management 📌 Regions ⚙️ Window Settings 💻 Virtual Terminal 📋 Copy and Paste 🚀 Subprocess Execution ⌨️ Key Binding 🌊 Flow Control 🧾 Termcap 💬 Message Line 📝 Logging 🏁 Startup 🧩 Miscellaneous 🔣 String Escapes 🌍 Environment Variables 📁 Files Referenced 🙏 Credits 🐛 Bugs 📦 Installation