screen

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SCREEN(1) SCREEN(1)






NAME

screen - screen manager with VT100/ANSI terminal emulation






SYNOPSIS
screen [ -options ] [ cmd [ args ] ]
screen -r [[pid.]tty[.host]]
screen -r sessionowner/[[pid.]tty[.host]]






DESCRIPTION

Screen is a full-screen window manager that multiplexes a physical ter-
minal between several processes (typically interactive shells). Each
virtual terminal provides the functions of a DEC VT100 terminal and, in
addition, several control functions from the ISO 6429 (ECMA 48, ANSI
X3.64) 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.


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 windows, turn out-
put logging on and off, copy-and-paste text between windows, view the
scrollback history, switch between windows in whatever manner you wish,
etc. All windows run their programs completely independent of each
other. Programs continue to run when their window is currently not vis-
ible and even when the whole screen session is detached from the user"s
terminal. When a program terminates, screen (per default) 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 win-
dow. 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.


Screen does not understand the prefix "C-" to mean control. Please use
the caret notation ("^A" instead of "C-a") as arguments to e.g. the
escape command or the -e option. Screen will also print out control
characters in caret notation.


The standard way to create a new window is to type "C-a c". This cre-
ates a new window running a shell and switches to that window immedi-
ately, 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 or at the "C-a :" command line) 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 (specified in the $STY environ-
ment variable) 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 "/var/run/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", "shut-
down", "rsend", "sccs" and other similar programs that use the utmp
file to determine who you are. As long as screen is active on your ter-
minal, the terminal"s 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 cor-
rectly selected your terminal type, just as you would for any other
termcap/terminfo program. (You can do this by using tset 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 "DEFAULT KEY
BINDINGS". The manual section "CUSTOMIZATION" deals with the contents
of your .screenrc.


If your terminal is a "true" auto-margin terminal (it doesn"t allow the
last position on the screen to be updated without scrolling the screen)
consider using 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. Most terminals nowadays have "magic"
margins (automatic margins plus usable last column). This is the VT100
style type and perfectly suited for screen. 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.






COMMAND-LINE OPTIONS
Screen has the following command-line options:


-a include all capabilities (with some minor exceptions) in each win-
dow"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 current termi-
nal. By default, screen tries to restore its old window sizes
when attaching to resizable terminals (those with "WS" in its
description, e.g. suncmd or some xterm).


-c file
override the default configuration file from "$HOME/.screenrc" to
file.


-d|-D [pid.tty.host]
does not start screen, but detaches 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. In
combination with the -r/-R option more powerful effects can be
achieved:


-d -r Reattach a session and if necessary detach it first.


-d -R Reattach a session and if necessary detach or even create it
first.


-d -RR Reattach a session and if necessary detach or create it. Use
the first session if more than one session is available.


-D -r Reattach a session. If necessary detach and logout remotely
first.


-D -R Attach here and now. In detail this means: If a session is run-
ning, then reattach. If necessary detach and logout remotely
first. If it was not running create it and notify the user.
This is the author"s favorite.


-D -RR Attach here and now. Whatever that means, just do it.


Note: It is always a good idea to check the status of your ses-
sions by means of "screen -list".


-e xy
specifies the command character to be x and the character generat-
ing 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". When creating a screen session, this option sets the
default command character. In a multiuser session all users added
will start off with this command character. But when attaching to
an already running session, this option changes only the command
character of the attaching user. This option is equivalent to
either the commands "defescape" or "escape" respectively.


-f, -fn, and -fa
turns flow-control on, off, or "automatic switching mode". This
can also be defined through the "defflow" .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 dis-
play immediately when flow-control is on. See the "defflow"
.screenrc command for details. The use of this option is discour-
aged.


-l and -ln
turns login mode on or off (for /var/run/utmp updating). This can
also be defined through the "deflogin" .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. If the session runs in multiuser
mode, it is marked "multi". Sessions marked as "unreachable"
either live on a different host or are "dead". An unreachable
session is considered dead, when its name matches either the name
of the local host, or the specified parameter, if any. See the -r
flag for a description how to construct matches. Sessions marked
as "dead" should be thoroughly checked and removed. Ask your sys-
tem administrator if you are not sure. Remove sessions with the
-wipe option.


-L tells screen to turn on automatic output logging for the windows.


-m causes screen to ignore the $STY environment variable. With
"screen -m" creation of a new session is enforced, regardless
whether screen is called from within another screen session or
not. This flag has a special meaning in connection with the "-d"
option:


-d -m Start screen in "detached" mode. This creates a new session but
doesn"t attach to it. This is useful for system startup
scripts.


-D -m This also starts screen in "detached" mode, but doesn"t fork a
new process. The command exits if the session terminates.


-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.


-p number_or_name
Preselect a window. This is usefull when you want to reattach to a
specific windor or you want to send a command via the "-X" option
to a specific window. As with screen"s select commant, "-" selects
the blank window. As a special case for reattach, "=" brings up
the windowlist on the blank window.


-q Suppress printing of error messages. In combination with "-ls" the
exit value is as follows: 9 indicates a directory without ses-
sions. 10 indicates a directory with running but not attachable
sessions. 11 (or more) indicates 1 (or more) usable sessions. In
combination with "-r" the exit value is as follows: 10 indicates
that there is no session to resume. 12 (or more) indicates that
there are 2 (or more) sessions to resume and you should specify
which one to choose. In all other cases "-q" has no effect.


-r [pid.tty.host]
-r sessionowner/[pid.tty.host]
resumes a detached screen session. No other options (except com-
binations with -d/-D) may be specified, though an optional prefix
of [pid.]tty.host may be needed to distinguish between multiple
detached screen sessions. The second form is used to connect to
another user"s screen session which runs in multiuser mode. This
indicates that screen should look for sessions in another user"s
directory. This requires setuid-root.


-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 had not been specified. The option is set
by default if screen is run as a login-shell (actually screen uses
"-xRR" in that case). For combinations with the -d/-D option see
there.


-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.


-S sessionname
When creating a new session, this option can be used to specify a
meaningful name for the session. This name identifies the session
for "screen -list" and "screen -r" actions. It substitutes the
default [tty.host] suffix.


-t name
sets the title (a.k.a.) for the default shell or specified pro-
gram. See also the "shelltitle" .screenrc command.


-U Run screen in UTF-8 mode. This option tells screen that your ter-
minal sends and understands UTF-8 encoded characters. It also sets
the default encoding for new windows to "utf8".


-v Print version number.


-wipe [match]
does the same as "screen -ls", but removes destroyed sessions
instead of marking them as "dead". An unreachable session is con-
sidered dead, when its name matches either the name of the local
host, or the explicitly given parameter, if any. See the -r flag
for a description how to construct matches.


-x Attach to a not detached screen session. (Multi display mode).


-X Send the specified command to a running screen session. You can
use the -d or -r option to tell screen to look only for attached
or detached screen sessions. Note that this command doesn"t work
if the session is password protected.






DEFAULT KEY BINDINGS
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 counter-
parts (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. See section "CUSTOMIZA-
TION" for a description of the command.




The following table shows the default key bindings:


C-a " (select) Prompt for a window name or number to switch
to.


C-a " (windowlist -b)
Present a list of all windows for selection.


C-a 0 (select 0)
... ...
C-a 9 (select 9)
C-a - (select -) Switch to window number 0 - 9, or to the
blank window.


C-a tab (focus) Switch the input focus to the next region.


C-a C-a (other) Toggle to the window displayed previously.
Note that this binding defaults to the com-
mand character typed twice, unless overrid-
den. For instance, if you use the option
"-e]x", this command becomes "]]".


C-a a (meta) Send the command character (C-a) to window.
See escape command.


C-a A (title) Allow the user to enter a name for the cur-
rent window.


C-a b
C-a C-b (break) Send a break to window.


C-a B (pow_break) Reopen the terminal line and send a break.


C-a c
C-a C-c (screen) Create a new window with a shell and switch
to that window.


C-a C (clear) Clear the screen.


C-a d
C-a C-d (detach) Detach screen from this terminal.


C-a D D (pow_detach) Detach and logout.


C-a f
C-a C-f (flow) Toggle flow on, off or auto.


C-a F (fit) Resize the window to the current region size.


C-a C-g (vbell) Toggles screen"s visual bell mode.


C-a h (hardcopy) Write a hardcopy of the current window to the
file "hardcopy.n".


C-a H (log) Begins/ends logging of the current window to
the file "screenlog.n".


C-a i
C-a C-i (info) Show info about this window.


C-a k
C-a C-k (kill) Destroy current window.


C-a l
C-a C-l (redisplay) Fully refresh current window.


C-a L (login) Toggle this windows login slot. Available
only if screen is configured to update the
utmp database.


C-a m
C-a C-m (lastmsg) Repeat the last message displayed in the mes-
sage line.


C-a M (monitor) Toggles monitoring of the current window.


C-a space
C-a n
C-a C-n (next) Switch to the next window.


C-a N (number) Show the number (and title) of the current
window.


C-a backspace
C-a h
C-a p
C-a C-p (prev) Switch to the previous window (opposite of C-
a n).


C-a q
C-a C-q (xon) Send a control-q to the current window.


C-a Q (only) Delete all regions but the current one.


C-a r
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
C-a C-s (xoff) Send a control-s to the current window.


C-a S (split) Split the current region into two new ones.


C-a t
C-a C-t (time) Show system information.


C-a v (version) Display the version and compilation date.


C-a C-v (digraph) Enter digraph.


C-a w
C-a C-w (windows) Show a list of window.


C-a W (width) Toggle 80/132 columns.


C-a x
C-a C-x (lockscreen) Lock this terminal.


C-a X (remove) Kill the current region.


C-a z
C-a C-z (suspend) Suspend screen. Your system must support
BSD-style job-control.


C-a Z (reset) Reset the virtual terminal to its "power-on"
values.


C-a . (dumptermcap) Write out a ".termcap" file.


C-a ? (help) Show key bindings.


C-a C- (quit) Kill all windows and terminate screen.


C-a : (colon) Enter command line mode.


C-a [
C-a C-[
C-a esc (copy) Enter copy/scrollback mode.


C-a ] (paste .) Write the contents of the paste buffer to the
stdin queue of the current window.


C-a {
C-a } (history) Copy and paste a previous (command) line.


C-a > (writebuf) Write paste buffer to a file.


C-a < (readbuf) Reads the screen-exchange file into the paste
buffer.


C-a = (removebuf) Removes the file used by C-a < and C-a >.


C-a , (license) Shows where screen comes from, where it went
to and why you can use it.


C-a _ (silence) Start/stop monitoring the current window for
inactivity.


C-a * (displays) Show a listing of all currently attached dis-
plays.






CUSTOMIZATION
The "socket directory" defaults either to $HOME/.screen or simply to
/tmp/screens or preferably to /var/run/screen chosen at compile-time.
If screen is installed setuid-root, then the administrator should com-
pile screen with an adequate (not NFS mounted) socket directory. If
screen is not running setuid-root, the user can specify any mode 700
directory in the environment variable $SCREENDIR.


When screen is invoked, it executes initialization commands from the
files "/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 (this override feature may be dis-
abled at compile-time). The user specific screenrc file is searched in
$SCREENRC, then $HOME/.screenrc. The command line option -c takes
precedence over the above user screenrc files.


Commands in these files are used to set options, bind functions to
keys, and to automatically establish one or more windows at the begin-
ning 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. Unintel-
ligible lines are warned about and ignored. Commands may contain ref-
erences to environment variables. The syntax is the shell-like "$VAR "
or "${VAR}". Note that this causes incompatibility with previous screen
versions, as now the "$"-character has to be protected with "" if no
variable substitution shall be performed. A string in single-quotes is
also protected from variable substitution.


Two configuration files are shipped as examples with your screen dis-
tribution: "etc/screenrc" and "etc/etcscreenrc". They contain a number
of useful examples for various commands.


Customization can also be done "on-line". To enter the command mode
type "C-a :". Note that commands starting with "def" change default
values, while others change current settings.


The following commands are available:


acladd usernames [crypted-pw]
addacl usernames


Enable users to fully access this screen session. Usernames can be one
user or a comma separated list of users. This command enables to attach
to the screen session and performs the equivalent of "aclchg usernames
+rwx "#?"". executed. To add a user with restricted access, use the
"aclchg" command below. If an optional second parameter is supplied,
it should be a crypted password for the named user(s). "Addacl" is a
synonym to "acladd". Multi user mode only.


aclchg usernames permbits list
chacl usernames permbits list


Change permissions for a comma separated list of users. Permission bits
are represented as "r", "w" and "x". Prefixing "+" grants the permis-
sion, "-" removes it. The third parameter is a comma separated list of
commands and/or windows (specified either by number or title). The spe-
cial list "#" refers to all windows, "?" to all commands. if usernames
consists of a single "*", all known users are affected. A command can
be executed when the user has the "x" bit for it. The user can type
input to a window when he has its "w" bit set and no other user obtains
a writelock for this window. Other bits are currently ignored. To
withdraw the writelock from another user in window 2: "aclchg username
-w+w 2". To allow read-only access to the session: "aclchg username -w
"#"". As soon as a user"s name is known to screen he can attach to the
session and (per default) has full permissions for all command and win-
dows. Execution permission for the acl commands, "at" and others should
also be removed or the user may be able to regain write permission.
Rights of the special username nobody cannot be changed (see the "su"
command). "Chacl" is a synonym to "aclchg". Multi user mode only.


acldel username


Remove a user from screen"s access control list. If currently attached,
all the user"s displays are detached from the session. He cannot attach
again. Multi user mode only.


aclgrp username [groupname]


Creates groups of users that share common access rights. The name of
the group is the username of the group leader. Each member of the group
inherits the permissions that are granted to the group leader. That
means, if a user fails an access check, another check is made for the
group leader. A user is removed from all groups the special value
"none" is used for groupname. If the second parameter is omitted all
groups the user is in are listed.


aclumask [[users]+bits |[users]-bits .... ]
umask [[users]+bits |[users]-bits .... ]


This specifies the access other users have to windows that will be cre-
ated by the caller of the command. Users may be no, one or a comma
separated list of known usernames. If no users are specified, a list of
all currently known users is assumed. Bits is any combination of
access control bits allowed defined with the "aclchg" command. The spe-
cial username "?" predefines the access that not yet known users will
be granted to any window initially. The special username "??" prede-
fines the access that not yet known users are granted to any command.
Rights of the special username nobody cannot be changed (see the "su"
command). "Umask" is a synonym to "aclumask".


activity message


When any activity occurs in a background window that is being moni-
tored, screen displays a notification in the message line. The notifi-
cation message can be re-defined by means of the "activity" command.
Each occurrence of "%" in message is replaced by the number of the win-
dow in which activity has occurred, and each occurrence of "^G" is
replaced by the definition for bell in your termcap (usually an audible
bell). The default message is


"Activity in window %n"


Note that monitoring is off for all windows by default, but can be
altered by use of the "monitor" command (C-a M).


allpartial on|off


If set to on, only the current cursor line is refreshed on window
change. This affects all windows and is useful for slow terminal
lines. The previous setting of full/partial refresh for each window is
restored with "allpartial off". This is a global flag that immediately
takes effect on all windows overriding the "partial" settings. It does
not change the default redraw behavior of newly created windows.


altscreen on|off


If set to on, "alternate screen" support is enabled in virtual termi-
nals, just like in xterm. Initial setting is "off".


at [identifier][#|*|%] command [args ... ]


Execute a command at other displays or windows as if it had been
entered there. "At" changes the context (the "current window" or "cur-
rent display" setting) of the command. If the first parameter describes
a non-unique context, the command will be executed multiple times. If
the first parameter is of the form "identifier*" then identifier is
matched against user names. The command is executed once for each dis-
play of the selected user(s). If the first parameter is of the form
"identifier%" identifier is matched against displays. Displays are
named after the ttys they attach. The prefix "/dev/" or "/dev/tty" may
be omitted from the identifier. If identifier has a "#" or nothing
appended it is matched against window numbers and titles. Omitting an
identifier in front of the "#", "*" or "%"-character selects all users,
displays or windows because a prefix-match is performed. Note that on
the affected display(s) a short message will describe what happened.
Permission is checked for initiator of the "at" command, not for the
owners of the affected display(s). Note that the "#" character works
as a comment introducer when it is preceded by whitespace. This can be
escaped by prefixing a "". Permission is checked for the initiator of
the "at" command, not for the owners of the affected display(s).
Caveat: When matching against windows, the command is executed at least
once per window. Commands that change the internal arrangement of win-
dows (like "other") may be called again. In shared windows the command
will be repeated for each attached display. Beware, when issuing toggle
commands like "login"! Some commands (e.g. "process") require that a
display is associated with the target windows. These commands may not
work correctly under "at" looping over windows.


attrcolor attrib [attribute/color-modifier]


This command can be used to highlight attributes by changing the color
of the text. If the attribute attrib is in use, the specified
attribute/color modifier is also applied. If no modifier is given, the
current one is deleted. See the "STRING ESCAPES" chapter for the syntax
of the modifier. Screen understands two pseudo-attributes, "i" stands
for high-intensity foreground color and "I" for high-intensity back-
ground color.


Examples:


attrcolor b "R"


Change the color to bright red if bold text is to be printed.


attrcolor u "-u b"


Use blue text instead of underline.


attrcolor b ".I"


Use bright colors for bold text. Most terminal emulators do this
already.


attrcolor i "+b"


Make bright colored text also bold.


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 com-
mand. When turned off, a hangup signal will terminate screen and all
the processes it contains. Autodetach is on by default.


autonuke on|off


Sets whether a clear screen sequence should nuke all the output that
has not been written to the terminal. See also "obuflimit".


backtick id lifespan autorefresh cmd args...
backtick id


Program the backtick command with the numerical id id. The output of
such a command is used for substitution of the "%"" string escape. The
specified lifespan is the number of seconds the output is considered
valid. After this time, the command is run again if a corresponding
string escape is encountered. The autorefresh parameter triggers an
automatic refresh for caption and hardstatus strings after the speci-
fied number of seconds. Only the last line of output is used for sub-
stitution.
If both the lifespan and the autorefresh parameters are zero, the back-
tick program is expected to stay in the background and generate output
once in a while. In this case, the command is executed right away and
screen stores the last line of output. If a new line gets printed
screen will automatically refresh the hardstatus or the captions.
The second form of the command deletes the backtick command with the
numerical id id.


bce [on|off]


Change background-color-erase setting. If "bce" is set to on, all char-
acters cleared by an erase/insert/scroll/clear operation will be dis-
played in the current background color. Otherwise the default back-
ground color is used.


bell_msg [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 this 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 "^G" is replaced by the definition for bell in your term-
cap (usually an audible bell). The default message is


"Bell in window %n"


An empty message can be supplied to the "bell_msg" command to suppress
output of a message line (bell_msg ""). Without parameter, the current
message is shown.


bind [-c class] key [command [args]]


Bind a command to a key. By default, most of the commands provided by
screen are bound to one or more keys as indicated in the "DEFAULT KEY
BINDINGS" section, e.g. the command 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 sin-
gle 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 command argument can be any command listed in this
section.


If a command class is specified via the "-c" option, the key is bound
for the specified class. Use the "command" command to activate a class.
Command classes can be used to create multiple command keys or multi-
character bindings.


Some examples:


bind " " windows
bind ^k
bind k
bind K kill
bind ^f screen telnet foobar
bind 33 screen -ln -t root -h 1000 9 su


would bind the space key to the command that displays a list of windows
(so that the command usually invoked by "C-a C-w" would also be avail-
able as "C-a space"). The next three lines remove the default kill
binding from "C-a C-k" and "C-a k". "C-a K" is then bound to the kill
command. Then it binds "C-f" to the command "create a window with a
TELNET connection to foobar", and bind "escape" to the command that
creates an non-login window with a.k.a. "root" in slot #9, with a supe-
ruser shell and a scrollback buffer of 1000 lines.


bind -c demo1 0 select 10
bind -c demo1 1 select 11
bind -c demo1 2 select 12
bindkey "^B" command -c demo1


makes "C-b 0" select window 10, "C-b 1" window 11, etc.


bind -c demo2 0 select 10
bind -c demo2 1 select 11
bind -c demo2 2 select 12
bind - command -c demo2


makes "C-a - 0" select window 10, "C-a - 1" window 11, etc.


bindkey [-d] [-m] [-a] [[-k|-t] string [cmd args]]


This command manages screen"s input translation tables. Every entry in
one of the tables tells screen how to react if a certain sequence of
characters is encountered. There are three tables: one that should con-
tain actions programmed by the user, one for the default actions used
for terminal emulation and one for screen"s copy mode to do cursor
movement. See section "INPUT TRANSLATION" for a list of default key
bindings.
If the -d option is given, bindkey modifies the default table, -m
changes the copy mode table and with neither option the user table is
selected. The argument string is the sequence of characters to which
an action is bound. This can either be a fixed string or a termcap key-
board capability name (selectable with the -k option).
Some keys on a VT100 terminal can send a different string if applica-
tion mode is turned on (e.g the cursor keys). Such keys have two
entries in the translation table. You can select the application mode
entry by specifying the -a option.
The -t option tells screen not to do inter-character timing. One cannot
turn off the timing if a termcap capability is used.
Cmd can be any of screen"s commands with an arbitrary number of args.
If cmd is omitted the key-binding is removed from the table.
Here are some examples of keyboard bindings:


bindkey -d
Show all of the default key bindings. The application mode entries are
marked with [A].


bindkey -k k1 select 1
Make the "F1" key switch to window one.


bindkey -t foo stuff barfoo
Make "foo" an abbreviation of the word "barfoo". Timeout is disabled so
that users can type slowly.


bindkey "24" mapdefault
This key-binding makes "^T" an escape character for key-bindings. If
you did the above "stuff barfoo" binding, you can enter the word "foo"
by typing "^Tfoo". If you want to insert a "^T" you have to press the
key twice (i.e. escape the escape binding).


bindkey -k F1 command
Make the F11 (not F1!) key an alternative screen escape (besides ^A).


break [duration]


Send a break signal for duration*0.25 seconds to this window. For non-
Posix systems the time interval may be rounded up to full seconds.
Most useful if a character device is attached to the window rather than
a shell process (See also chapter "WINDOW TYPES"). The maximum duration
of a break signal is limited to 15 seconds.


blanker


Activate the screen blanker. First the screen is cleared. If no blanker
program is defined, the cursor is turned off, otherwise, the program is
started and it"s output is written to the screen. The screen blanker
is killed with the first keypress, the read key is discarded.
This command is normally used together with the "idle" command.


blankerprg [program args]


Defines a blanker program. Disables the blanker program if no arguments
are given.


breaktype [tcsendbreak|TIOCSBRK |TCSBRK]


Choose one of the available methods of generating a break signal for
terminal devices. This command should affect the current window only.
But it still behaves identical to "defbreaktype". This will be changed
in the future. Calling "breaktype" with no parameter displays the
break method for the current window.


bufferfile [exchange-file]


Change the filename used for reading and writing with the paste buffer.
If the optional argument to the "bufferfile" command is omitted, the
default setting ("/tmp/screen-exchange") is reactivated. The following
example will paste the system"s password file into the screen window
(using the paste buffer, where a copy remains):


C-a : bufferfile /etc/passwd
C-a < C-a ]
C-a : bufferfile


c1 [on|off]


Change c1 code processing. "C1 on" tells screen to treat the input
characters between 128 and 159 as control functions. Such an 8-bit
code is normally the same as ESC followed by the corresponding 7-bit
code. The default setting is to process c1 codes and can be changed
with the "defc1" command. Users with fonts that have usable characters
in the c1 positions may want to turn this off.


caption always|splitonly [string]
caption string [string]


This command controls the display of the window captions. Normally a
caption is only used if more than one window is shown on the display
(split screen mode). But if the type is set to always screen shows a
caption even if only one window is displayed. The default is splitonly.


The second form changes the text used for the caption. You can use all
escapes from the "STRING ESCAPES" chapter. Screen uses a default of
"%3n %t".


You can mix both forms by providing a string as an additional argument.


charset set


Change the current character set slot designation and charset mapping.
The first four character of set are treated as charset designators
while the fifth and sixth character must be in range "0" to "3" and set
the GL/GR charset mapping. On every position a "." may be used to indi-
cate that the corresponding charset/mapping should not be changed (set
is padded to six characters internally by appending "." chars). New
windows have "BBBB02" as default charset, unless a "encoding" command
is active.
The current setting can be viewed with the "info" command.


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.


clear


Clears the current window and saves its image to the scrollback buffer.


colon [prefix]


Allows you to enter ".screenrc" command lines. Useful for on-the-fly
modification of key bindings, specific window creation and changing
settings. Note that the "set" keyword no longer exists! Usually com-
mands affect the current window rather than default settings for future
windows. Change defaults with commands starting with "def...".


If you consider this as the "Ex command mode" of screen, you may regard
"C-a esc" (copy mode) as its "Vi command mode".


command [-c class]


This command has the same effect as typing the screen escape character
(^A). It is probably only useful for key bindings. If the "-c" option
is given, select the specified command class. See also "bind" and
"bindkey".


compacthist [on|off]


This tells screen whether to suppress trailing blank lines when
scrolling up text into the history buffer.


console [on|off]


Grabs or un-grabs the machines console output to a window. Note: Only
the owner of /dev/console can grab the console output. This command is
only available if the machine supports the ioctl TIOCCONS.


copy


Enter copy/scrollback mode. This allows you to copy text from the cur-
rent 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.
B, E move the cursor WORD by WORD (as in vi).
C-u and C-d scroll the display up/down by the specified amount of
lines while preserving the cursor position. (Default: half screen-
full).
C-b and C-f scroll the display up/down a full screen.
g moves to the beginning of the buffer.
% jumps to the specified percentage of the buffer.


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 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 repeat count 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
paste buffer.
Searching:
/ Vi-like search forward.
? Vi-like search backward.
C-a s Emacs style incremental search forward.
C-r Emacs style reverse i-search.
Specials:
There are however some keys that act differently than in vi. Vi
does not allow one 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.
Example: Try this on a rather full text screen: "C-a [ M 20 l SPACE
c 10 l 5 j C SPACE".


This moves one to the middle line of the screen, moves in 20
columns left, marks the beginning of the paste buffer, sets the
left column, moves 5 columns down, sets the right column, and then
marks the end of the paste buffer. Now try:
"C-a [ M 20 l SPACE 10 l 5 j SPACE"


and notice the difference in the amount of text copied.
J joins lines. It toggles between 4 modes: lines separated by a new-
line character (012), lines glued seamless, lines separated by a
single whitespace and comma separated lines. Note that you can
prepend the newline character with a carriage return character, by
issuing a "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 con-
tents of the paste buffer will not be overwritten, but is appended
to.
A toggles in append mode and sets a (second) mark.
> sets the (second) mark and writes the contents of the paste buffer
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 $ >".
C-g gives information about the current line and column.
x exchanges the first mark and the current cursor position. You can
use this to adjust an already placed mark.
@ does nothing. Does not even exit copy mode.
All keys not described here exit copy mode.


copy_reg [key]


No longer exists, use "readreg" instead.


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 (default) only "LF" is used. When no
parameter is given, the state is toggled.


debug on|off


Turns runtime debugging on or off. If screen has been compiled with
option -DDEBUG debugging available and is turned on per default. Note
that this command only affects debugging output from the main "SCREEN"
process correctly. Debug output from attacher processes can only be
turned off once and forever.


defc1 on|off


Same as the c1 command except that the default setting for new windows
is changed. Initial setting is "on".


defautonuke on|off


Same as the autonuke command except that the default setting for new
displays is changed. Initial setting is "off". Note that you can use
the special "AN" terminal capability if you want to have a dependency
on the terminal type.


defbce on|off


Same as the bce command except that the default setting for new windows
is changed. Initial setting is "off".


defbreaktype [tcsendbreak|TIOCSBRK |TCSBRK]


Choose one of the available methods of generating a break signal for
terminal devices. The preferred methods are tcsendbreak and TIOCSBRK.
The third, TCSBRK, blocks the complete screen session for the duration
of the break, but it may be the only way to generate long breaks.
Tcsendbreak and TIOCSBRK may or may not produce long breaks with spikes
(e.g. 4 per second). This is not only system dependant, this also dif-
fers between serial board drivers. Calling "defbreaktype" with no
parameter displays the current setting.


defcharset [set]


Like the charset command except that the default setting for new win-
dows is changed. Shows current default if called without argument.


defescape xy


Set the default command characters. This is equivalent to the "escape"
except that it is useful multiuser sessions only. In a multiuser ses-
sion "escape" changes the command character of the calling user, where
"defescape" changes the default command characters for users that will
be added later.


defflow on|off|auto [interrupt]


Same as the flow command except that the default setting for new win-
dows is changed. Initial setting is "auto". Specifying "defflow auto
interrupt" is the same as the command-line options -fa and -i.


defgr on|off


Same as the gr command except that the default setting for new windows
is changed. Initial setting is "off".


defhstatus [status]


The hardstatus line that all new windows will get is set to status.
This command is useful to make the hardstatus of every window display
the window number or title or the like. Status may contain the same
directives as in the window messages, but the directive escape charac-
ter is "^E" (octal 005) instead of "%". This was done to make a misin-
terpretation of program generated hardstatus lines impossible. If the
parameter status is omitted, the current default string is displayed.
Per default the hardstatus line of new windows is empty.


defencoding enc


Same as the encoding command except that the default setting for new
windows is changed. Initial setting is the encoding taken from the ter-
minal.


deflog on|off


Same as the log command except that the default setting for new windows
is changed. Initial setting is "off".


deflogin on|off


Same as the login command except that the default setting for new win-
dows is changed. This is initialized with "on" as distributed (see con-
fig.h.in).


defmode mode


The mode of each newly allocated pseudo-tty is set to mode. Mode is an
octal number. When no "defmode" command is given, mode 0622 is used.


defmonitor on|off


Same as the monitor command except that the default setting for new
windows is changed. Initial setting is "off".


defnonblock on|off|numsecs


Same as the nonblock command except that the default setting for dis-
plays is changed. Initial setting is "off".


defobuflimit limit


Same as the obuflimit command except that the default setting for new
displays is changed. Initial setting is 256 bytes. Note that you can
use the special "OL" terminal capability if you want to have a depen-
dency on the terminal type.


defscrollback num


Same as the scrollback command except that the default setting for new
windows is changed. Initial setting is 100.


defshell command


Synonym to the shell command. See there.


defsilence on|off


Same as the silence command except that the default setting for new
windows is changed. Initial setting is "off".


defslowpaste msec"


Same as the slowpaste command except that the default setting for new
windows is changed. Initial setting is 0 milliseconds, meaning "off".


defutf8 on|off


Same as the utf8 command except that the default setting for new win-
dows is changed. Initial setting is "on" if screen was started with
"-U", otherwise "off".


defwrap on|off


Same as the wrap command except that the default setting for new win-
dows is changed. Initially line-wrap is on and can be toggled with the
"wrap" command ("C-a r") or by means of "C-a : wrap on|off".


defwritelock on|off|auto


Same as the writelock command except that the default setting for new
windows is changed. Initially writelocks will off.


defzombie [keys]


Synonym to the zombie command. Both currently change the default. See
there.


detach [-h]


Detach the screen session (disconnect it from the terminal and put it
into the background). This returns you to the shell where you invoked
screen. A detached screen can be resumed by invoking screen with the
-r option (see also section "COMMAND-LINE OPTIONS"). The -h option
tells screen to immediately close the connection to the terminal
("hangup").


dinfo


Show what screen thinks about your terminal. Useful if you want to know
why features like color or the alternate charset don"t work.


displays


Shows a tabular listing of all currently connected user front-ends
(displays). This is most useful for multiuser sessions.


digraph [preset]


This command prompts the user for a digraph sequence. The next two
characters typed are looked up in a builtin table and the resulting
character is inserted in the input stream. For example, if the user
enters "a"", an a-umlaut will be inserted. If the first character
entered is a 0 (zero), screen will treat the following characters (up
to three) as an octal number instead. The optional argument preset is
treated as user input, thus one can create an "umlaut" key. For exam-
ple the command "bindkey ^K digraph """" enables the user to generate
an a-umlaut by typing CTRL-K a.


dumptermcap


Write the termcap entry for the virtual terminal optimized for the cur-
rently 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 con-
verter like captoinfo and then compile the entry with tic.


echo [-n] message


The echo command may be used to annoy screen users with a "message of
the day". Typically installed in a global /etc/screenrc. The option
"-n" may be used to suppress the line feed. See also "sleep". Echo is
also useful for online checking of environment variables.


encoding enc [enc]


Tell screen how to interpret the input/output. The first argument sets
the encoding of the current window. Each window can emulate a different
encoding. The optional second parameter overwrites the encoding of the
connected terminal. It should never be needed as screen uses the locale
setting to detect the encoding. There is also a way to select a termi-
nal encoding depending on the terminal type by using the "KJ" termcap
entry.


Supported encodings are eucJP, SJIS, eucKR, eucCN, Big5, GBK, KOI8-R,
CP1251, UTF-8, ISO8859-2, ISO8859-3, ISO8859-4, ISO8859-5, ISO8859-6,
ISO8859-7, ISO8859-8, ISO8859-9, ISO8859-10, ISO8859-15, jis.


See also "defencoding", which changes the default setting of a new win-
dow.


escape xy


Set the command character to x and the character generating a literal
command character (by triggering the "meta" command) to y (similar to
the -e option). Each argument is either a single character, a two-
character sequence of the form "^x" (meaning "C-x"), a backslash fol-
lowed 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".


eval command1 [command2 ...]


Parses and executes each argument as separate command.


exec [[fdpat] newcommand [args ...]]


Run a unix subprocess (specified by an executable path newcommand and
its optional arguments) in the current window. The flow of data between
newcommands stdin/stdout/stderr, the process originally started in the
window (let us call it "application-process") and screen itself (win-
dow) is controlled by the filedescriptor pattern fdpat. This pattern
is basically a three character sequence representing stdin, stdout and
stderr of newcommand. A dot (.) connects the file descriptor to screen.
An exclamation mark (!) causes the file descriptor to be connected to
the application-process. A colon (:) combines both. User input will go
to newcommand unless newcommand receives the application-process" out-
put (fdpats first character is "!" or ":") or a pipe symbol (|) is
added (as a fourth character) to the end of fdpat.
Invoking "exec" without arguments shows name and arguments of the cur-
rently running subprocess in this window. Only one subprocess a time
can be running in each window.
When a subprocess is running the "kill" command will affect it instead
of the windows process.
Refer to the postscript file "doc/fdpat.ps" for a confusing illustra-
tion of all 21 possible combinations. Each drawing shows the digits
2,1,0 representing the three file descriptors of newcommand. The box
marked "W" is the usual pty that has the application-process on its
slave side. The box marked "P" is the secondary pty that now has
screen at its master side.


Abbreviations:
Whitespace between the word "exec" and fdpat and the command can be
omitted. Trailing dots and a fdpat consisting only of dots can be omit-
ted. A simple "|" is synonymous for the pattern "!..|"; the word exec
can be omitted here and can always be replaced by "!".


Examples:


exec ... /bin/sh
exec /bin/sh
!/bin/sh


Creates another shell in the same window, while the original shell is
still running. Output of both shells is displayed and user input is
sent to the new /bin/sh.


exec !.. stty 19200
exec ! stty 19200
!!stty 19200
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