screen(1)
NAME
screen - screen manager with VT100/ANSI terminal emulation
SYNOPSIS
screen [ -options ] [ cmd [ args ] ]
screen -r [ [pid.]tty[.host] ]
DESCRIPTION
Screen is a full-screen window manager that multiplexes a physical
terminal between several processes (typically interactive shells). Each
virtual terminal provides the functions of the DEC VT100 terminal and, in
addition, several control functions from the ANSI X3.64 (ISO 6429) and
ISO 2022 standards (e.g. insert/delete line and support for multiple
character sets). There is a scrollback history buffer for each virtual
terminal and a copy-and-paste mechanism that allows moving text regions
between windows.
The name of this program was changed to iScreen to be able to distinguish
it from Oliver Laumann's original screen program. Despite that fact, this
manual will continue to use the name screen. This is, because often the
binary is installed as 'screen'.
When screen is called, it creates a single window with a shell in it (or
the specified command) and then gets out of your way so that you can use
the program as you normally would. Then, at any time, you can create new
(full-screen) windows with other programs in them (including more
shells), kill existing windows, view a list of the current windows, turn
output logging on and off, copy-and-paste text between windows, view the
scrollback history, switch between windows in whatever manner you wish,
etc. When a program terminates, screen kills the window that contained
it. If this window was in the foreground, the display switches to the
previous window; if none are left, screen exits.
Everything you type is sent to the program running in the current window.
The only exception to this is the one keystroke that is used to initiate
a command to the window manager. By default, each command begins with a
control-a (abbreviated C-a from now on), and is followed by one other
keystroke. The command character and all the key bindings can be fully
customized to be anything you like, though they are always two characters
in length.
The standard way to create a new window is to type "C-a c". This creates
a new window running a shell and switches to that window immediately,
regardless of the state of the process running in the current window.
Similarly, you can create a new window with a custom command in it by
first binding the command to a keystroke (in your .screenrc file) and
then using it just like the "C-a c" command. In addition, new windows
can be created by running a command like:
screen emacs prog.c
from a shell prompt within a previously created window. This will not
run another copy of screen, but will instead supply the command name and
its arguments to the window manager who will use it to create the new
window. The above example would start the emacs editor (editing prog.c)
and switch to its window.
If "/etc/utmp" is writable by screen, an appropriate record will be
written to this file for each window, and removed when the window is
terminated. This is useful for working with "talk", "script",
"shutdown", "rsend", "sccs" and other similar programs that use the utmp
file to determine who you are. As long as screen is active on your
terminal, the terminals own record is removed from the utmp file. See
also "C-a L".
GETTING STARTED
Before you begin to use screen you'll need to make sure you have
correctly selected your terminal type, just as you would for any other
termcap/terminfo program. (You can do this by using tset or stty, for
example.)
If you're impatient and want to get started without doing a lot more
reading, you should remember this one command: "C-a ?". Typing these
two characters will display a list of the available screen commands and
their bindings. Each keystroke is discussed in the section "COMMAND
KEYS". The manual section "CUSTOMIZATION" deals with the contents of your
.screenrc.
If possible, choose a version of your terminal's termcap that has
automatic margins turned off. This will ensure an accurate and optimal
update of the screen in all circumstances. The next best thing is an
auto-margin terminal that allows the last position on the screen to be
updated without scrolling the screen (such as a vt100). This also allows
the entire screen to be updated. Lastly, if all you've got is a "true"
auto-margin terminal screen will be content to use it, but updating a
character put into the last position on the screen may not be possible
until the screen scrolls or the character is moved into a safe position
in some other way. This delay can be shortened by using a terminal with
insert-character capability.
If your terminal is of the second type (firm-margined `am'), you will
want to let screen know about this, since a normal termcap doesn't
distinguish this type of automatic margins from a "true" `am' terminal.
You do this by specifying the `LP' capability in your termcap (see the
"termcap" .screenrc command), or by using the -L command-line option.
Screen needs this information to correctly update the screen.
If you are using a "true" auto-margin terminal (no `LP') at low baud
rates, you may want to turn on a more optimal output mode by including
the flag `OP' in your termcap entry, or by specifying the -O command-line
option. The trade-off is that screen will no-longer accurately emulate
the vt100's line-end quirks (e.g. the screen will scroll after putting
one character in the last screen position).
COMMAND KEYS
As mentioned, each screen command consists of a "C-a" followed by one
other character. For your convenience, all commands that are bound to
lower-case letters are also bound to their control character counterparts
(with the exception of "C-a a"; see below), thus, "C-a c" as well as "C-a
C-c" can be used to create a window.
The following keystroke commands are available:
C-a 0 - C-a 9 (select0 - select9)
Switch to the window with the number 0 through 9. When a new window
is established, the first available number from the range 0..9 is
assigned to this window. Thus, the first window can be activated by
"C-a 0" (there can be no more than 10 windows present at any one
time).
C-a C-a (other)
Switch to the window displayed previously. Note that this function
defaults to the command character typed twice, unless overridden;
for instance, if you use the option "-e]x", this function becomes
"]]", not "]C-a".
C-a a
Send the command character (C-a) to the processes in the current
window.
C-a A (aka)
Allow the user to enter an a.k.a (also-known-as). for the current
window.
C-a c or C-a C-c (shell)
Create a new window with a shell and switch to that window.
C-a C (clear)
Clear the screen (saves image to scrollback buffer).
C-a d or C-a C-d (detach)
Detach screen (disconnect it from the terminal and put it into the
background). A detached screen can be resumed by invoking screen
with the -r option. (See also section "COMMAND-LINE OPTIONS".)
C-a D (pow_detach)
Power detach. Mainly the same as above, but also sends a HANGUP
signal to the parent process of screen. CAUTION: This will result
in a logout, when screen was started from your login shell.
C-a f or C-a C-f (flow)
Cycles the current window's flow-control setting from "automatic" to
"on" to "off", see the section titled FLOW-CONTROL for details.
C-a C-g (vbell)
Toggles screen's visual bell mode. If your terminal does not support
a visual bell, a `vbell-message' is displayed in the status line.
C-a h or C-a C-h (hardcopy)
Write a hardcopy of the current window to the file "hardcopy.n" in
the window's default directory, where n is the number of the current
window.
C-a H (log)
Begins/ends logging of the current window to the file "screenlog.n"
in the window's default directory, where n is the number of the
current window. The session log is appended to the previous
contents of the file if it already exists. The current contents and
the contents of the scrollback history are not included in the
session log.
C-a i or C-a C-i (info)
Uses the message line to display some information about the current
window: the cursor position in the form "(column,row)" starting
with "(1,1)", the terminal width and height plus the size of the
scrollback buffer in lines, like in "(80,24)+50", various flag
settings (flow-control, insert mode, origin mode, wrap mode,
application-keypad mode, output logging, activity monitoring, and
redraw (`+' indicates enabled, `-' not)), the currently active
character set (G0, G1, G2, or G3), and in square brackets the
terminal character sets that are currently designated as G0 through
G3. For system information use "C-a t".
C-a k or C-a C-k (kill)
Kill the current window and switch to the previously displayed
window. Note: Emacs users should keep this command in mind, when
killing a line. It is recommended not to use "C-a" as the screen
escape key or that kill is rebound to "C-a K".
C-a l or C-a C-l (redisplay)
Redisplay the current window.
C-a L (login)
Adds or removes the entry in /etc/utmp file for the current window.
This controls if the window is `logged in'. See also above.
Additionally to that toggle, it is convenient having a `log in' and
a `log out' key. E.g. `bind I set login on' and `bind O set login
off' will map these keys to be C-a I and C-a O.
C-a m or C-a C-m (lastmsg)
Repeat the last message displayed in the message line. Useful if
you're typing when a message appears, because (unless your terminal
has a status line) the message goes away when you press a key.
C-a M (monitor)
Toggles monitoring of the current window. When monitoring is turned
on and the affected window is switched into the background, you will
receive the activity notification message in the status line at the
first sign of output and the window will also be marked with an `@'
in the window-status display. Monitoring is initially off for all
windows.
C-a space or C-a n or C-a C-n (next)
Switch to the next window. This function can be used repeatedly to
cycle through the list of windows. (Some terminals require you to
release the control key before pressing space.)
C-a p or C-a C-p (prev)
Switch to the previous window (the opposite of C-a n).
C-a q or C-a C-q (xon)
Send a control-q to the program in the current window.
C-a r or C-a C-r (wrap)
Toggle the current window's line-wrap setting (turn the current
window's automatic margins on and off).
C-a s or C-a C-s (xoff)
Send a control-s to the program in the current window.
C-a t or C-a C-t (time)
Uses the message line to display the time of day, the host name, and
the load averages over 1, 5, and 15 minutes (if this is available on
your system). For window specific information use "C-a i".
C-a v or C-a C-v (version)
Display the version and compilation date.
C-a w or C-a C-w (windows)
Uses the message line to display a list of all the windows. Each
window is listed by number with the name of process that has been
started in the window (or its a.k.a.); the current window is marked
with a `*'; the previous window is marked with a `-'; all the
windows that are "logged in" are marked with a `$'; a background
window that has received a bell is marked with a `!'; a background
window that is being monitored and has had activity occur is marked
with an `@'; a window which has output logging turned on is marked
with `(L)'.
C-a W (width)
Toggle the window width between 80 and 132 columns. As this command
became a toggle, "C-a N" is no longer supported. This requires a
capable terminal and the termcap entries "Z0" and "Z1". See the
"termcap" command in section "CUSTOMIZATION" for more information.
C-a x or C-a C-x (lock)
Call a screenlock program (/local/bin/lck or /usr/bin/lock or a
builtin, if no other is available). Screen does not accept any
command keys until this program terminates. Meanwhile processes in
the windows may continue, as the windows are in the `detached'
state. The screenlock program may be changed through the environment
variable $LOCKPRG (which must be set in the shell from which screen
is started) and is executed with the user's uid and gid.
C-a z or C-a C-z (suspend)
Suspend screen. The windows are in the `detached' state, while
screen is suspended.
C-a Z (reset)
Reset the virtual terminal to its "power-on" values.
C-a . (termcap)
Write the termcap entry for the virtual terminal of the currently
active window to the file ".termcap" in the user's "$HOME/.screen"
directory (or wherever screen stores its sockets. See the "FILES"
section below). This termcap entry is identical to the value of the
environment variable $TERMCAP that is set up by screen for each
window. For terminfo based systems you will need to run a converter
like captoinfo and then compile the entry with tic.
C-a ? (help)
Displays a help screen showing you all the key bindings. The first
pages list all the internal commands followed by their bindings.
Subsequent pages will display the custom commands, one command per
key. Press space when you're done reading each page, or return to
exit early. All other characters are ignored, except for the
command character, which will exit the help display and begin a
command.
C-a C-\ (quit)
Kill all windows and terminate screen. Note that on vt100-style
terminals the keys C-4 and C-\ are identical. So be careful not to
write C-a C-4 when selecting window no. 4. Use the empty bind
command (as in "bind '^'") to remove a key binding.
C-a : (colon)
Allows you to enter ".screenrc" command lines as well as names of
key-bound-functions. Useful for on-the-fly modification of key
bindings, specific window creation and changing settings. Settings
of the current window can be changed by prepending the command (if
appropriate) with the keyword "set". If you consider this as the
`Ex command mode' of screen, you may regard "C-a esc" as its `Vi
command mode'.
C-a [ or C-a C-[ or C-a esc (copy)
Enter copy/scrollback mode. This allows you to copy text from the
current window and its history into the paste buffer. In this mode a
vi-like `full screen editor' is active:
Movement keys:
h, j, k, l move the cursor line by line or column by column.
0, ^ and $ move to the leftmost column, to the first or last non-
whitespace character on the line.
H, M and L move the cursor to the leftmost column of the top, center
or bottom line of the window.
+ and - positions one line up and down.
G moves to the specified absolute line (default: end of buffer).
| moves to the specified absolute column.
w, b, e move the cursor word by word.
C-u and C-d scroll the display up/down by the specified amount of
lines while preserving the cursor position. (Default: half
screenfull).
C-b and C-f scroll the display up/down a full screen.
g moves to the beginning of the buffer, whereas
% jumps to the specified percentage.
Note: Emacs style movement keys can be customized by a .screenrc
command. (E.g. markkeys "h=^B:l=^F:$=^E") There is no simple method
for a full emacs-style keymap, as this involves multi-character
codes.
Marking:
The copy range is specified by setting two marks. The text between
these marks will be highlighted. Press space to set the first or
second mark respectively.
Y and y can be used to mark one whole line or to mark from start of
line.
W marks exactly one word.
Repeat count:
Any of these commands can be prefixed with a number (by pressing
digits 0..9) which is taken as a repeat count. Example: "C-a C-[ H
10 j 5 Y" will copy lines 11 to 15 into the pastebuffer.
Specials:
There are however some keys that act differently here and in vi. Vi
does not allow to yank rectangular blocks of text, but screen does.
Press
c or C to set the left or right margin respectively. If no repeat
count is given, both default to the current cursor position. Try
this on a rather full text screen as an example: "C-A [ S-M 20 l
SPACE c 10 l 5 j S-C SPACE".
J joins lines. It toggles between 3 modes: lines separated by a
newline character (012), lines glued seamless, lines separated by a
single whitespace. Note that you can prepend the newline character
with a carriage return character, by issuing a "set crlf on".
v is for all the vi users with ":set numbers" - it toggles the left
margin between column 9 and 1.
Press a before the final space key to toggle in append mode. Thus
the contents of the pastebuffer will not be overwritten, but
appended to.
A toggles in append mode and sets a (second) mark.
> sets the (second) mark and writes the contents of the copybuffer
to the screen-exchange file (/tmp/screen-exchange per default) once
copy-mode is finished. This example demonstrates how to dump the
whole scrollback buffer to that file: "C-A [ g SPACE G $ >".
? gives information about the current line and column.
C-a ] or C-a C-] (paste)
Paste. Write the contents of the paste buffer to the stdin queue of
the current window.
C-a { (history)
Usually users work with a shell that allows easy access to previous
commands. E.g. csh has the command "!!" to repeat the last command
executed. Screen allows you to have a primitive way of re-calling
"the command that started ...": You just type the first letter of
that command, then hit `C-a {' and screen tries to find a previous
line that matches with the `prompt character' to the left of the
cursor. This line is pasted into this window's input queue. Thus
you have a crude command history (made up by the visible window and
its scrollback buffer).
C-a > (write_buffer)
Writes the contents of the paste buffer to a public accessible
screen-exchange file. This is thought of as a primitive means of
communication between screen users on the same host. See also "C-a
esc".
C-a < (read_buffer)
Reads the screen-exchange file into the pastebuffer. See also "C-a
]".
C-a = (kill_buffer)
Removes the exchange file used by "C-a <" and "C-a >".
COMMAND-LINE OPTIONS
Screen has the following command-line options:
-a include all capabilities (with some minor exceptions) in each
window's termcap, even if screen must redraw parts of the display in
order to implement a function.
-A Adapt the sizes of all windows to the size of the display. By
default, screen may try to restore its old window sizes.
-c file
override the default configuration file from "$HOME/.screenrc" to
file.
-d|-D [pid.tty.host]
does not start screen, but detach the elsewhere running screen
session. It has the same effect as typing "C-a d" from screen's
controlling terminal. -D is the equivalent to the power detach key.
If no session can be detached, this option is ignored. The
combination "screen -D -r" can be used to `transport' the elsewhere
running session to this terminal and logout there. Note: It is a
good idea to have the status of your sessions checked by means of
"screen -list".
-e xy
specifies the command character to be x and the character generating
a literal command character to y (when typed after the command
character). The default is "C-a" and `a', which can be specified as
"-e^Aa". See the "escape" .screenrc command for more details.
-f, -fn, and -fa
turns flow-control on, off, or "automatic switching mode". This can
also be defined through the "flow" .screenrc command.
-h num
Specifies the history scrollback buffer to be num lines high.
-i will cause the interrupt key (usually C-c) to interrupt the display
immediately when flow-control is on. See the "flow" .screenrc
command for details.
-l and -ln
turns login mode on or off (for /etc/utmp updating). This can also
be defined through the "login" .screenrc command.
-ls and -list
does not start screen, but prints a list of pid.tty.host strings
identifying your screen sessions. Sessions marked `detached' can be
resumed with "screen -r". Those marked `attached' are running and
have a controlling terminal. Sessions marked as `dead' should be
thoroughly checked and removed. Ask your system administrator if you
are not sure. Remove sessions with the -wipe option.
5 -m disables looking in environment variable $STY for an alternate
socket name.
-t name or -k name
sets the title (a.k.a.) for the default shell or specified program.
See also the "shellaka" .screenrc command.
-wipe
does the same as "screen -ls", but removes destroyed sessions
instead of marking them as `dead'.
-L tells screen your auto-margin terminal has a writable last-position
on the screen. This can also be set in your .screenrc by specifying
`LP' in a "termcap" command.
-O selects a more optimal output mode for your terminal rather than
true vt100 emulation (only affects auto-margin terminals without
`LP'). This can also be set in your .screenrc by specifying `OP' in
a "termcap" command.
-r [pid.tty.host]
resumes a detached screen session. No other options (except "-d -r"
or "-D -r") may be specified, though an optional prefix of
[pid.]tty.host may be needed to distinguish between multiple
detached screen sessions.
-R attempts to resume the first detached screen session it finds. If
successful, all other command-line options are ignored. If no
detached session exists, starts a new session using the specified
options, just as if -R were not specified.
-s sets the default shell to the program specified, instead of the
value in the environment variable $SHELL (or "/bin/sh" if not
defined). This can also be defined through the "shell" .screenrc
command.
CUSTOMIZATION
The "socket directory" defaults either to $HOME/.screen or preferably to
/local/screens. If screen is installed setuid-root, then the
administrator should compile screen with an adequate (not NFS mounted)
SOCKDIR. If screen is not running setuid-root, the user can specify any
mode 777 directory in the environment variable $SCREENDIR.
When screen is invoked, it executes initialization commands from the
files "/local/etc/screenrc" and ".screenrc" in the user's home directory.
These are the "programmer's defaults" that can be overridden in the
following ways: For the global screenrc file screen searches for the
environment variable $SYSSCREENRC. The user specific screenrc file is
searchend in $ISCREENRC, then $SCREENRC, then $HOME/.iscreenrc and
finally defaults to $HOME/.screenrc. The command line option -c takes
precedence over the user specific screenrc file. Commands in these files
are used to set options, bind functions to keys, and to automatically
establish one or more extra windows at the beginning of your screen
session. Commands are listed one per line, with empty lines being
ignored. A command's arguments are separated by tabs or spaces, and may
be surrounded by single or double quotes. A `#' turns the rest of the
line into a comment, except in quotes. Unintelligible lines are warned
about and ignored. Commands may contain references to environment
variables. The syntax is the shell-like "$VAR " or "${VAR}". Note that
this causes incompatibilities with previous screen versions, as now the
'$'-sign has to be protected with '' if no variable substitution shall be
performed.
Customization can also be done 'on-line'. To enter the command mode type
`C-a :'. Setting flags (like scrollback, login, etc.) on-line may not
have the desired effect, as e.g. the command "C-a : login on" will affect
only the settings for the creation of new windows (just like within
.screenrc). If you intend to change flags of the current window, then
prepend the command with the keyword "set". E.g. "C-a : set login on"
will log this window in.
The following initialization commands are available:
activity message
When any activity occurs in a background window that is being monitored,
screen displays a notification in the message line. The notification
message can be re-defined by means of the "activity" command. Each
occurrence of `%' in message is replaced by the number of the window in
which activity has occurred, and each occurrence of `~' is replaced by
the definition for bell in your termcap (usually an audible bell). The
default message is
'Activity in window %'
Note that monitoring is off for all windows by default, but can be
altered by use of the "monitor" command (C-a M).
autodetach on|off
Sets whether screen will automatically detach upon hangup, which saves
all your running programs until they are resumed with a screen -r
command. When turned off, a hangup signal will terminate screen and all
the processes it contains. Autodetach is on by default.
bell message
When a bell character is sent to a background window, screen displays a
notification in the message line. The notification message can be re-
defined by means of the "bell" command. Each occurrence of `%' in
message is replaced by the number of the window to which a bell has been
sent, and each occurrence of `~' is replaced by the definition for bell
in your termcap (usually an audible bell). The default message is
'Bell in window %'
An empty message can be supplied to the "bell" command to suppress output
of a message line (bell "").
bind key [function [args]]
Bind a function to a key. By default, each function provided by screen
is bound to one or more keys as indicated by the above table, e.g. the
function to create a new window is bound to "C-c" and "c". The "bind"
command can be used to redefine the key bindings and to define new
bindings. The key argument is either a single character, a two-character
sequence of the form "^x" (meaning "C-x"), a backslash followed by an
octal number (specifying the ASCII code of the character), or a backslash
followed by a second character, such as "\^" or "\\". The argument can
also be quoted, if you like. If no further argument is given, any
previously established binding for this key is removed. The function
argument can be one of the following keywords:
select0 Switch to window #0
...
select9 Switch to window #9
aka Change the current window's a.k.a.
clear Clear the screen
colon Enter one ".screenrc" command on-the-fly.
copy Select a piece of text.
detach Detach screen
flow Toggle the current window's flow-control setting
hardcopy Make hardcopy of current window
history Use cut&paste to fetch a recently displayed line.
help Display a list of the key bindings in effect
info Display the current window's status information
kill Kill the current window
lastmsg Redisplay the last message line
lock Run a screenlock program.
log Begin/end logging of the current window's output
login Toggle the window's "login" setting (/etc/utmp
entry)
monitor Toggle activity monitoring of the current window
next Switch to the next window
other Switch to the window displayed previously
paste Paste in a selected piece of text.
pow_detach Detach screen and logout.
prev Switch to the previous window
quit Kill all windows and terminate
readbuffer Take text from the exchange file.
redisplay Redisplay current window
reset Reset the window to its "power-on" settings
screen Create a new window with the specified command
shell Create a new window with a shell
suspend Suspend screen
termcap Write screen's termcap entry to $HOME/.screencap
vbell Toggle the window's "vbell" setting.
version Display the version numbers and date last modified
width Toggle the terminal width between 80 and 132 columns
windows Display a list of all windows
wrap Toggle the current window's line-wrap setting
writebuffer Store the selected text in the exchange file.
xoff Send a control-s to the current program
xon Send a control-q to the current program
Some examples:
bind ' ' windows
bind ^f screen telnet foobar
bind \033 screen -ln -t root -h 1000 9 su
would bind the space key to the function that displays a list of windows
(so that the function usually invoked by "C-a C-w" would also be
available as "C-a space"), bind "C-f" to the function "create a window
with a TELNET connection to foobar", and bind "escape" to the function
that creates an non-login window with a.k.a. "root" in slot #9, with a
super-user shell and a scrollbackbuffer of 1000 lines.
bufferfile exchange-file
Change the filename used for reading and writing with the copybuffer.
The default is "/tmp/screen-exchange". The following example will paste
the system's password file into the screen window:
C-a : bufferfile /etc/passwd
C-a < C-a ]
chdir [directory]
Change the current directory of screen to the specified directory or, if
called without an argument, to your home directory (the value of the
environment variable $HOME). All windows that are created by means of
the "screen" command from within ".screenrc" or by means of "C-a : screen
..." or "C-a c" use this as their default directory. Without a chdir
command, this would be the directory from which screen was invoked.
Hardcopy and log files are always written to the window's default
directory, not the current directory of the process running in the
window. You can use this command multiple times in your .screenrc to
start various windows in different default directories, but the last
chdir value will affect all the windows you create interactively.
crlf on|off
This affects the copying of text regions with the `C-a [' command. If it
is set to `on', lines will be separated by the two character sequence
`CR' - `LF'. Otherwise only `LF' is used.
echo [-n] message
The echo command may be used to annoy screen users with a 'message of the
day'. Typically installed in a global /local/etc/screenrc. See also
"sleep". Echo is also useful for online checking of environment
variables.
escape xy
Set the command character to x and the character generating a literal
command character to y (just like in the -e option). Each argument is
either a single character, a two-character sequence of the form "^x"
(meaning "C-x"), a backslash followed by an octal number (specifying the
ASCII code of the character), or a backslash followed by a second
character, such as "\^" or "\\". The default is "^Aa", but "``" is
recommended by one of the authors.
flow on|off|auto [interrupt]
Sets the default flow-control mode for new windows. Specifying "flow
auto interrupt" is the same as the command-line options -fa and -i. See
the discussion on FLOW-CONTROL later on in this document for full details
and note, that this is subject to change in future releases.
hardcopy_append on|off
If set to "on", screen will append to the "hardcopy.n" files created by
the command "C-a h", otherwise these files are overwritten each time.
hardstatus on|off
Toggles the use of the terminals hardware status line. If "on", screen
will use this facility to display one line messages. Otherwise these
messages are overlayed in reverse video mode at the display line. Note
that the hardstatus feature should only be used, if the termcap/terminfo
capabilities "hs", "ts", "fs" and "ds" are set properly.
login on|off
Sets the login flag which determines if new windows should have /etc/utmp
entries added for them. The login state is also changeable on-the-fly by
using the bindable version of the "login" command (C-a L) of by means of
"C-a : set login on|off". The default should be "on" for a screen that
runs under suid-root.
markkeys string
This is a method of changing the keymap used for copy/history mode. The
string is made up of oldchar=newchar pairs which are separated by `:'.
Example: The string "B=^B:F=^F" will change the keys `C-b' and `C-f' from
their (original emacs-style bindings) to the vi style binding (scroll
up/down full page), which is the default meaning of `B' and `F'.
mode mode
The mode of each newly allocated pseudo-tty is set to mode. Mode is an
octal number. When no "mode" command is given, mode 0622 is used.
monitor on|off
Toggles activity monitoring of windows. When monitoring is turned on and
an affected window is switched into the background, you will receive the
activity notification message in the status line at the first sign of
output and the window will also be marked with an `@' in the window-
status display. Monitoring is initially off for all windows.
msgminwait sec
Defines the time screen delays all activity after a message was
dispayled. The default is 1 second.
msgwait sec
Defines the time a message is displayed, if screen is not disturbed by
other activity. The default is 5 seconds.
nethack on|off
Changes the kind of error messages used by screen. When you are familiar
with the game "nethack", you may enjoy the nethack-style messages which
will often blur the facts a little, but are much funnier to read. Anyway,
standard messages often tend to be unclear as well.
This option is only available if screen was compiled with the NETHACK
flag defined. The default setting is then determined by the presence of
the environment variable $NETHACKOPTIONS.
password [crypted_pw]
Present a crypted password in your ".screenrc" file and screen will ask
for it, whenever a detached session is tried to be resumed. This is
useful, if you have privileged programs running under screen and you want
to protect your session from reattach attempts by users that managed to
have your uid. (I.e. any superuser.)
pow_detach_msg message
The message specified here is output whenever a `Power detach' was
performed. It may be used as a replacement for a logout message or to
reset baud rate, etc.
screen [-opts] [n] [cmd [args]]
Establish a new window. The flow-control options (-f, -fn and -fa),
title (a.k.a.) option (-t), login options (-l and -ln) , terminal type
option (-T <term>) and scrollback option (-h <num>) may be specified for
each command. If an optional number n in the range 0..9 is given, the
window number n is assigned to the newly created window (or, if this
number is already in-use, the next available number). If a command is
specified after "screen", this command (with the given arguments) is
started in the window; otherwise, a shell is created. Thus, if your
".screenrc" contains the lines
# example for .screenrc:
screen 1
screen -fn -t foobar 2 telnet foobar
screen creates a shell window (in window #1) and a window with a TELNET
connection to the machine foobar (with no flow-control using the a.k.a.
"foobar" in window #2). If you do not include any screen commands in
your ".screenrc" file, then screen defaults to creating a single shell
window, number zero. When the initialization is completed, screen
switches to the last window specified in your .screenrc file or, if none,
it opens default window #0.
scrollback num
Set the size of the scrollback buffer for new windows to num lines. The
default scrollback is 50 lines. Use "C-a : set scrollback num" to change
the scrollback size of the current window and use "C-a i" to view the
current setting.
redraw on|off
Define whether the display should be refreshed (as done with "C-a l")
after switching to the current window. As usual when the "set" keyword is
given, this command only affects the current window. But unlike other
commands, "redraw off" (without "set") affects all windows, the window
specific settings come into effect again when "redraw on" (without "set")
is entered.
shell command
Set the command to be used to create a new shell. This overrides the
value of the environment variable $SHELL, or "/bin/sh" if undefined.
This is useful if you'd like to run a tty-enhancer which is expecting to
execute the program specified in $SHELL.
shellaka a.k.a.
Set the a.k.a. for all shells created during startup or by the C-A C-c
command. For details about what a.k.a.'s are, see the discussion
entitled ALSO KNOWN AS.
sleep num This command will pause the execution of a .screenrc file for
num seconds. It may be used to give users a chance to read the messages
output by "echo".
slowpaste usec
Define the speed text is inserted by the paste ("C-a ]") command. For
each 80 characters (IOSIZE) pasted screen will make a pause of usec
milliseconds to allow the application the processing of input. Use that,
if you have to fear that your underlying system chokes on large pastes.
startup_message on|off
Select whether to display the copyright notice when screen starts up.
term term
In each window's environment screen opens, it sets the $TERM variable to
"screen" by default, unless no description for "screen" is installed in
the local termcap or terminfo data base. In that case it pretends that
the terminal emulator is "vt100". This won't do much harm, as screen is
VT100/ANSI compatible. The use of the "term" command is discouraged for
non-default purpose. That is, one may want to specify special $TERM
settings (e.g. vt100) for the next "screen rlogin othermachine" command.
Use the command "screen -T vt100 rlogin othermachine" rather than setting
("term vt100") and resetting ("term screen") the default before and after
the "screen" command.
termcap term terminal-tweaks [window-tweaks]
terminfo term terminal-tweaks [window-tweaks]
Use this command to modify your terminal's termcap entry without going
through all the hassles involved in creating a custom termcap entry.
Plus, you can optionally customize the termcap generated for the windows.
If your system works with terminfo-database rather than with termcap
screen will understand the `terminfo' command which has the same effects
as the `termcap' command. Thus users can write one .screenrc file that
handles both cases, although terminfo syntax is slightly different from
termcap syntax.
The first argument specifies which terminal(s) should be affected by this
definition. You can specify multiple terminal names by separating them
with `|'s. Use `*' to match all terminals and `vt*' to match all
terminals that begin with "vt".
Each tweak argument contains one or more termcap defines (separated by
`:'s) to be inserted at the start of the appropriate termcap entry,
enhancing it or overriding existing values. The first tweak modifies
your terminal's termcap, and contains definitions that your terminal uses
to perform certain functions. Specify a null string to leave this
unchanged (e.g. ''). The second (optional) tweak modifies all the window
termcaps, and should contain definitions that screen understands (see the
"VIRTUAL TERMINAL" section).
Some examples:
termcap xterm* LP:hs@
Informs screen that all terminals that begin with `xterm' have firm auto-
margins that allow the last position on the screen to be updated (LP),
but they don't really have a status line (no 'hs' -- append `@' to turn
entries off). Note that we assume `LP' for all terminal names that start
with "vt", but only if you don't specify a termcap command for that
terminal.
termcap vt* LP
termcap vt102|vt220 Z0=\E[?3h:Z1=\E[?3l
Specifies the firm-margined `LP' capability for all terminals that begin
with `vt', and the second line will also add the escape-sequences to
switch into (Z0) and back out of (Z1) 132-character-per-line mode if this
is a vt102 or vt220. (You must specify Z0 and Z1 in your termcap to use
the width-changing commands.)
termcap vt100 "" l0=PF1:l1=PF2:l2=PF3:l3=PF4
This leaves your vt100 termcap alone and adds the function key labels to
each window's termcap entry.
termcap h19|z19 am@:im=\E@:ei=\EO dc=\E[P
Takes a h19 or z19 termcap and turns off auto-margins (am@) and enables
the insert mode (im) and end-insert (ei) capabilities (the `@' in the
`im' string is after the `=', so it is part of the string). Having the
`im' and `ei' definitions put into your terminal's termcap will cause
screen to automatically advertise the character-insert capability in each
window's termcap. Each window will also get the delete-character
capability (dc) added to its termcap, which screen will translate into a
line-update for the terminal (we're pretending it doesn't support
character deletion).
If you would like to fully specify each window's termcap entry, you
should instead set the $SCREENCAP variable prior to running screen. See
the discussion on the "VIRTUAL TERMINAL" in this manual, and the
termcap(5) man page for more information on termcap definitions.
vbell on|off
Sets the visual bell setting for new windows. If your terminal does not
support a visual bell a message is printed to the status line. The
default message is "Wuff, Wuff!!".
vbell_msg message
Sets the visual bell message. message is printed to the status line if
the window receives a bell character (^G) and vbell is set to "on".
vbellwait sec
Define a delay in seconds after each display of screen 's visual bell
message. The default is 0 seconds.
wrap on|off
Sets the line-wrap setting for new windows. When line-wrap is on, the
second consecutive printable character output at the last column of a
line will wrap to the start of the following line. As an added feature,
backspace (^H) will also wrap through the left margin to the previous
line. Line-wrap is on by default and can be toggled with the "wrap"
command ("C-a r") or by means of "C-a : set wrap on|off".
THE MESSAGE LINE
Screen displays informational messages and other diagnostics in a message
line at the bottom of the screen. If your terminal has a status line
defined in its termcap, screen will use this for displaying its messages,
otherwise the last line of the screen will be temporarily overwritten and
output will be momentarily interrupted. The message line is
automatically removed after a few seconds delay, but it can also be
removed early (on terminals without a status line) by beginning to type.
The message line facility can be used by an application running in the
current window by means of the ANSI Privacy message control sequence.
For instance, from within the shell, try something like:
echo '<esc>^Hello world<esc>\\'
where '<esc>' is an escape, '^' is a literal up-arrow, and '\\' turns
into a single backslash.
FLOW-CONTROL
Each window has a flow-control setting that determines how screen deals
with the XON and XOFF characters (and perhaps the interrupt character).
When flow-control is turned off, screen ignores the XON and XOFF
characters, which allows the user to send them to the current program by
simply typing them (useful for the emacs editor, for instance). The
trade-off is that it will take longer for output from a "normal" program
to pause in response to an XOFF. With flow-control turned on, XON and
XOFF characters are used to immediately pause the output of the current
window. You can still send these characters to the current program, but
you must use the appropriate two-character screen commands (typically "C-
a q" (xon) and "C-a s" (xoff)). The xon/xoff commands are also useful
for typing C-s and C-q past a terminal that intercepts these characters.
Each window has an initial flow-control value set with either the -f
option or the "flow" .screenrc command. Per default the windows are set
to automatic flow-switching. It can then be toggled between the three
states 'fixed on', 'fixed off' and 'automatic' interactively with the
"flow" command bound to "C-a f".
The automatic flow-switching mode deals with flow control using the
TIOCPKT mode (like "rlogin" does). If the tty driver does not support
TIOCPKT, screen tries to find out the right mode based on the current
setting of the application keypad -- when it is enabled, flow-control is
turned off and visa versa. Of course, you can still manipulate flow-
control manually when needed.
If you're running with flow-control enabled and find that pressing the
interrupt key (usually C-c) does not interrupt the display until another
6-8 lines have scrolled by, try running screen with the "interrupt"
option (add the "interrupt" flag to the "flow" command in your .screenrc,
or use the -i command-line option). This causes the output that screen
has accumulated from the interrupted program to be flushed. One
disadvantage is that the virtual terminal's memory contains the non-
flushed version of the output, which in rare cases can cause minor
inaccuracies in the output. For example, if you switch screens and
return, or update the screen with "C-a l" you would see the version of
the output you would have gotten without "interrupt" being on. Also, you
might need to turn off flow-control (or use auto-flow mode to turn it off
automatically) when running a program that expects you to type the
interrupt character as input, as it is possible to interrupt the output
of the virtual terminal to your physical terminal when flow-control is
enabled. If this happens, a simple refresh of the screen with "C-a l"
will restore it. Give each mode a try, and use whichever mode you find
more comfortable.
ALSO KNOWN AS (A.K.A.s)
You can customize each window's name in the window display (viewed with
the "windows" command (C-a w)) by setting it with one of the a.k.a.
commands. Normally the name displayed is the actual command name of the
program created in the window. However, it is sometimes useful to
distinguish various programs of the same name or to change the name on-
the-fly to reflect the current state of the window.
The default name for all shell windows can be set with the "shellaka"
command in the .screenrc file, while all other windows are created with a
"screen" command and thus can have their name set with the -t option.
Interactively, there is the AKA-string escape-sequence (<esc>kname<esc>\)
and the "aka" command (C-a A). The former can be output from an
application to control the window's name under software control, and the
latter will prompt for a name when typed. You can also bind pre-defined
names to keys with the "aka" command to set things quickly without
prompting.
Finally, screen has a shell-specific heuristic that is enabled by setting
the window's name to "search|name" and arranging to have a null aka
escape-sequence output as a part of your prompt. The search portion
specifies an end-of-prompt search string, while the name portion
specifies the default shell name for the window. If the name ends in a
`:' screen will add what it believes to be the current command running
in the window to the end of the window's shell name (e.g. "name:cmd").
Otherwise the current command name supersedes the shell name while it is
running.
Here's how it works: you must modify your shell prompt to output a null
aka escape-sequence (<esc>k<esc>\) as a part of your prompt. The last
part of your prompt must be the same as the string you specified for the
search portion of the a.k.a. Once this is set up, screen will use the
aka escape-sequence to clear the previous command name and get ready for
the next command. Then, when a newline is received from the shell, a
search is made for the end of the prompt. If found, it will grab the
first word after the matched string and use it as the command name. If
the command name begins with either '!', '%', or '^' screen will use the
first word on the following line (if found) in preference to the just-
found name. This helps csh users get better command names when using job
control or history recall commands.
Here's some .screenrc examples:
screen -t top 2 nice top
Adding this line to your .screenrc would start a niced version of the
"top" command in window 2 name "top" rather than "nice".
shellaka '> |csh'
screen 1
This file would start a shell using the given shellaka. The a.k.a.
specified is an auto-aka that would expect the prompt and the typed
command to look something like the following:
/usr/joe/src/dir> trn
(it looks after the '> ' for the command name). The window status would
show the name "trn" while the command was running, and revert to "csh"
upon completion.
bind R screen -t '% |root:' su
Having this command in your .screenrc would bind the key sequence "C-a R"
to the "su" command and give it an auto-aka name of "root:". For this
auto-aka to work, the screen could look something like this:
% !em
emacs file.c
Here the user typed the csh history command "!em" which ran the
previously entered "emacs" command. The window status would show
"root:emacs" during the execution of the command, and revert to simply
"root:" at its completion.
bind o aka
bind E aka ""
bind u aka (unknown)
The first binding doesn't have any arguments, so it would prompt you for
an a.k.a. when you type "C-a o". The second binding would clear an auto-
aka's current setting (C-a E). The third binding would set the current
window's a.k.a. to "(unknown)" (C-a u).
One thing to keep in mind when adding a null aka escape-sequence to your
prompt is that some shells (like the csh) count all the non-control
characters as part of the prompt's length. If these invisible characters
aren't a multiple of 8 then backspacing over a tab will result in an
incorrect display. One way to get around this is to use a prompt like
this:
set prompt='^[[0000m^[k^[\% '
The escape-sequence "<esc>[0000m" not only normalizes the character
attributes, but all the zeros round the length of the invisible
characters up to 8. Bash users will probably want to echo the escape
sequence in the PROMPT_COMMAND:
PROMPT_COMMAND='echo -n -e "\033k\033\134"'
(I used "134" to output a `\' because of a bug in v1.04).
THE VIRTUAL TERMINAL
Usually screen tries to emulate as much of the VT100/ANSI standard as
possible. But if your terminal lacks certain capabilities the emulation
may not be complete. In these cases screen has to tell the applications
that some of the features are missing. This is no problem on machines
using termcap, because screen can use the $TERMCAP variable to customize
the standard screen termcap.
But if you do a rlogin on another machine or your machine supports only
terminfo this method fails. Because of this screen offers a way to deal
with these cases. Here is how it works:
When screen tries to figure out a terminal name for itself, it first
looks for an entry named "screen.<term>", where <term> is the contents of
your $TERM variable. If no such entry exists, screen tries "screen" (or
"screen-w", if the terminal is wide (132 cols or more)). If even this
entry cannot be found, "vt100" is used as a substitute.
The idea is that if you have a terminal which doesn't support an
important feature (e.g. delete char or clear to EOS) you can build a new
termcap/terminfo entry for screen (named "screen.<dumbterm>") in which
this capability has been disabled. If this entry is installed on your
machines you are able to do a rlogin and still keep the correct
termcap/terminfo entry. The terminal name is put in the $TERM variable
of all new windows. Screen also sets the $TERMCAP variable reflecting
the capabilities of the virtual terminal emulated. Notice that, however,
on machines using the terminfo database this variable has no effect.
Furthermore, the variable $WINDOW is set to the window number of each
window.
The actual set of capabilities supported by the virtual terminal depends
on the capabilities supported by the physical terminal. If, for
instance, the physical terminal does not support underscore mode, screen
does not put the `us' and `ue' capabilities into the window's $TERMCAP
variable, accordingly. However, a minimum number of capabilities must be
supported by a terminal in order to run screen; namely scrolling, clear
screen, and direct cursor addressing (in addition, screen does not run on
hardcopy terminals or on terminals that over-strike).
Also, you can customize the $TERMCAP value used by screen by using the
"termcap" .screenrc command, or by defining the variable $SCREENCAP prior
to startup. When the latter defined, its value will be copied verbatim
into each window's $TERMCAP variable. This can either be the full
terminal definition, or a filename where the terminal "screen" (and/or
"screen-w") is defined.
Note that screen honors the "terminfo" .screenrc command if the system
uses the terminfo database rather than termcap.
When the boolean `G0' capability is present in the termcap entry for the
terminal on which screen has been called, the terminal emulation of
screen supports multiple character sets. This allows an application to
make use of, for instance, the VT100 graphics character set or national
character sets. The following control functions from ISO 2022 are
supported: lock shift G0 (SI), lock shift G1 (SO), lock shift G2, lock
shift G3, single shift G2, and single shift G3. When a virtual terminal
is created or reset, the ASCII character set is designated as G0 through
G3. When the `G0' capability is present, screen evaluates the
capabilities `S0', `E0', and `C0' if present. `S0' is the sequence the
terminal uses to enable and start the graphics character set rather than
SI. `E0' is the corresponding replacement for SO. `C0' gives a character
by character translation string that is used during semi-graphics mode.
This string is built like the `acsc' terminfo capability.
When the `po' and `pf' capabilities are present in the terminal's termcap
entry, applications running in a screen window can send output to the
printer port of the terminal. This allows a user to have an application
in one window sending output to a printer connected to the terminal,
while all other windows are still active (the printer port is enabled and
disabled again for each chunk of output). As a side-effect, programs
running in different windows can send output to the printer
simultaneously. Data sent to the printer is not displayed in the window.
Some capabilities are only put into the $TERMCAP variable of the virtual
terminal if they can be efficiently implemented by the physical terminal.
For instance, `dl' (delete line) is only put into the $TERMCAP variable
if the terminal supports either delete line itself or scrolling regions.
Note that this may provoke confusion, when the session is reattached on a
different terminal, as the value of $TERMCAP cannot be modified by parent
processes.
The following is a list of control sequences recognized by screen. "(V)"
and "(A)" indicate VT100-specific and ANSI- or ISO-specific functions,
respectively.
ESC E
Next Line
ESC D
Index
ESC M
Reverse Index
ESC H
Horizontal Tab Set
ESC 7 (V) Save Cursor and Attributes
ESC 8 (V) Restore Cursor and Attributes
ESC [s (A) Save Cursor and Attributes
ESC [u (A) Restore Cursor and Attributes
ESC c
Reset to Initial State
ESC = (V) Application Keypad Mode
ESC > (V) Numeric Keypad Mode
ESC # 8 (V) Fill Screen with E's
ESC \ (A) String Terminator
ESC ^ (A) Privacy Message String (Message Line)
ESC k
A.k.a. Definition String
ESC P (A) Device Control String
Outputs a string directly to the host
terminal without interpretation.
ESC _ (A) Application Program Command (not used)
ESC ] (A) Operating System Command (not used)
Control-N (A) Lock Shift G1 (SO)
Control-O (A) Lock Shift G0 (SI)
ESC n (A) Lock Shift G2
ESC o (A) Lock Shift G3
ESC N (A) Single Shift G2
ESC O (A) Single Shift G3
ESC ( Pcs (A) Designate character set as G0
ESC ) Pcs (A) Designate character set as G1
ESC * Pcs (A) Designate character set as G2
ESC + Pcs (A) Designate character set as G3
ESC [ Pn ; Pn H
Direct Cursor Addressing
ESC [ Pn ; Pn f
Direct Cursor Addressing
ESC [ Pn J
Erase in Display
Pn = None or 0
From Cursor to End of Screen
1
From Beginning of Screen to Cursor
2
Entire Screen
ESC [ Pn K
Erase in Line
Pn = None or 0
From Cursor to End of Line
1
From Beginning of Line to Cursor
2
Entire Line
ESC [ Pn A
Cursor Up
ESC [ Pn B
Cursor Down
ESC [ Pn C
Cursor Right
ESC [ Pn D
Cursor Left
ESC [ Ps ;...; Ps m
Select Graphic Rendition
Ps = None or 0
Default Rendition
1
Bold
2 (A) Faint
3 (A) Standout Mode (ANSI: Italicized)
4
Underlined
5
Blinking
7
Negative Image
22 (A) Normal Intensity
23 (A) Standout Mode off (ANSI: Italicized off)
24 (A) Not Underlined
25 (A) Not Blinking
27 (A) Positive Image
ESC [ Pn g
Tab Clear
Pn = None or 0
Clear Tab at Current Position
3
Clear All Tabs
ESC [ Pn ; Pn r (V) Set Scrolling Region
ESC [ Pn I (A) Horizontal Tab
ESC [ Pn Z (A) Backward Tab
ESC [ Pn L (A) Insert Line
ESC [ Pn M (A) Delete Line
ESC [ Pn @ (A) Insert Character
ESC [ Pn P (A) Delete Character
ESC [ Ps ;...; Ps h
Set Mode
ESC [ Ps ;...; Ps l
Reset Mode
Ps = 4 (A) Insert Mode
?3 (V) Change Terminal Width
?5 (V) Visible Bell (On followed by Off)
?6 (V) Origin Mode
?7 (V) Wrap Mode
ESC [ 5 i (A) Start relay to printer (ANSI Media Copy)
ESC [ 4 i (A) Stop relay to printer (ANSI Media Copy)
ENVIRONMENT
COLUMNS Number of columns on the terminal (overrides termcap
entry).
HOME Directory in which to look for .screenrc.
ISCREENRC Alternate user screenrc file.
LINES Number of lines on the terminal (overrides termcap
entry).
LOCKPRG Screen lock program.
NETHACKOPTIONS Turns on nethack option.
PATH Used for locating programs to run.
SCREENCAP For customizing a terminal's TERMCAP value.
SCREENDIR Alternate socket directory.
SCREENRC Alternate user screenrc file.
SHELL Default shell program for opening windows (default
"/bin/sh").
STY Alternate socket name.
SYSSCREENRC Alternate system screenrc file.
TERM Terminal name.
TERMCAP Terminal description.
FILES
$SYSSCREENRC
/local/etc/screenrc screen initialization commands
$ISCREENRC
$SCREENRC
$HOME/.iscreenrc
$HOME/.screenrc Read in after /local/etc/screenrc
$ISCREENDIR/S-<login>
$SCREENDIR/S-<login>
/local/screens/S-<login> Socket directories (default)
/usr/tmp/screens/S-<login> Alternate socket directories.
<socket directory>/.termcap Written by the "termcap" output function
/usr/tmp/screens/screen-exchange or
/tmp/screen-exchange screen `interprocess communication buffer'
hardcopy.[0-9] Screen images created by the hardcopy function
screenlog.[0-9] Output log files created by the log function
/usr/lib/terminfo/?/* or
/etc/termcap Terminal capability databases
/etc/utmp Login records
$LOCKPRG Program that locks a terminal.
SEE ALSO
termcap(5), utmp(5), vi(1), captoinfo(1), tic(1)
AUTHORS
Originally created by Oliver Laumann, this latest version was produced by
Wayne Davison, Juergen Weigert and Michael Schroeder.
CONTRIBUTORS
Allan Ball, Bart Schaefer, Doug Siebert, Howard Chu, Jay Vassos-Libove,
John Kraft, Larry Virden, Marc Boucher, Nathan Glasser, Patrick Wolfe,
Rudolf Koenig. Toerless Eckert,
VERSION
This is version 3.2. It's roots are a merge of a custom version 2.3PR7 by
Wayne Davison and several enhancements to Oliver Laumann's version 2.0.
Note that all versions numbered 2.x are copyright by Oliver Laumann.
BUGS
`dm' (delete mode), `xn', and `xs' are not handled correctly (they are
ignored).
The GR set of ISO 2022 is not supported.
There is no keyboard input translation to VT100 sequences.
It is not possible to change the environment variable $TERMCAP when
reattaching under a different terminal type.
The support of terminfo based systems is very limited. Adding extra
capabilities to $TERMCAP may not have any effects.
Screen does not make use of hardware tabs.
Screen must be installed as set-uid with owner root in order to be able
to correctly change the owner of the tty device file for each window.
Special permission may also be required to write the file "/etc/utmp".
Entries in "/etc/utmp" are not removed when screen is killed with
SIGKILL. This will cause some programs (like "w" or "rwho") to advertise
that a user is logged on who really isn't.