Man page for apt-get screen Command
This tutorial shows the man page for man screen in linux.
Open terminal with 'su' access and type the command as shown below:
man screen
Result of the Command Execution shown below:
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. Note that you cannot transport environment variables from the
invoking shell to the application (emacs in this case), because it is
forked from the parent screen process, not from the invoking shell.
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
and creation timestamps identifying your screen sessions. Ses
sions 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 param
eter, 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 system 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 useful when you want to reattach to a
specific window or you want to send a command via the " X" option
to a specific window. As with screen's select command, " " 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 youngest (in terms of creation time)
detached screen session it finds. If successful, all other com
mand 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. Note: Time
based session selection is a Debian addition.
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).
Screen refuses to attach from within itself. But when cascading
multiple screens, loops are not detected; take care.
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.
See also split, remove, only.
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. See
also split, remove, focus.
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 horizontally into
two new ones. See also only, remove, focus.
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. See also split,
only, focus.
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 | (split v) Split the current region vertically into two
new ones.
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 `
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