screen
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 a 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.
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 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 (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 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
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 environment 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 "/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
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 correctly 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 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. Note
that a `xv' together with an `am' flag effects like `LP'.
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-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
current terminal. By default, screen tries to restore
its old window sizes when attaching to resizeable
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. 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 "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 display immediately when flow-control is on. See
the "defflow" .screenrc command for details. The use
of this option is discouraged.
-l and -ln
turns login mode on or off (for /etc/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. 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 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.
-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.
-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
had not been specified. The option is set by default if
screen is run as a login-shell.
-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 program. See also the "shelltitle" .screenrc
command.
-v Print version number.
-wipe
does the same as "screen -ls", but removes destroyed
sessions instead of marking them as `dead'.
-x Attach to a not detached screen session. (Multi display
mode).
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 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. See section "CUSTOMIZATION"
for a description of the command.
The following table shows the default key bindings:
C-a '
C-a " (select) Prompt for a window name or number
to switch to.
C-a 0 (select 0)
... ...
C-a 9 (select 9) Switch to window number 0 - 9.
C-a C-a (other) Toggle to the window displayed
previously. Note that this
binding 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 (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 current 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 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 message 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 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 t
C-a C-t (time) Show system information.
C-a v
C-a C-v (version) Display the version and
compilation date.
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 z
C-a C-z (suspend) Suspend
screen.Yoursystemmustsupport
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 pastebuffer to a file.
C-a < (readbuf) Reads the screen-exchange file
into the pastebuffer.
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.
CUSTOMIZATION
The "socket directory" defaults either to $HOME/.screen or
simply to /tmp/screens or preferably to /usr/local/screens
chosen at compile-time. If screen is installed setuid-root,
then the administrator should compile screen with an
adequate (not NFS mounted) socket directory. 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 "/usr/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 (this override feature may be disabled
at compile-time). The user specific screenrc file is
searched in $ISCREENRC, then $SCREENRC, then
$HOME/.iscreenrc and finally defaults to $HOME/.screenrc.
The command line option -c takes precedence over the above
user screenrc files.
Commands in these files are used to set options, bind
functions to keys, and to automatically establish one or
more windows at the beginning of your screen session.
Commands are listed one per line, with empty lines being
ignored. A command's arguments are separated by tabs or
spaces, and may be surrounded by single or double quotes. A
`#' turns the rest of the line into a comment, except in
quotes. Unintelligible lines are warned about and ignored.
Commands may contain references to environment variables.
The syntax is the shell-like "$VAR " or "${VAR}". Note that
this causes incompatibility with previous screen versions,
as now the '$'-character has to be protected with '\' if no
variable substitution shall be performed. A string in
single-quotes is also protected from variable substitution.
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 username
Enable a user to (fully) access this screen session.
Necessary to allow other users to attach to this screen
session. Same as `aclchg username +rwx "#?"'. Multi user
mode only.
aclchg username permbits list
Change a users permissions. Permission bits are represented
as `r', `w' and `x'. Prefixing `+' grants the permission,
`-' removes it. The third parameter is a komma seperated
list of commands or windows (specified either by number or
title). The special list `#' refers to all windows, `?' to
all commands. 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.
Multi user mode only.
acldel username
Remove a user from screens access control list. If currently
attached, all the users displays are detached from the
session. He cannot attach again. Multi user mode only.
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).
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".
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 `current 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 display
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 ommited 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.
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.
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".
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 [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
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 command argument can be any
command listed in this section.
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 command that displays a list
of windows (so that the command usually invoked by "C-a C-w"
would also be available as "C-a space"), bind "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
super-user shell and a scrollback buffer of 1000 lines.
break [duration]
Send a break signal for duration*0.25 seconds to this
window. Most useful if a character device is attached to
the window rather than a shell process.
bufferfile [exchange-file]
Change the filename used for reading and writing with the
copybuffer. 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:
C-a : bufferfile /etc/passwd
C-a < C-a ]
C-a : bufferfile
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
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 commands 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'.
console [on|off]
Grabs or ungrabs the machines console output to a window.
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 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 pastebuffer.
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
copybuffer, sets the left column, moves 5 columns down,
sets the right column, and then marks the end of the
copybuffer. 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 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 "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 is 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 "C-A [ g SPACE G $ >".
C-g gives information about the current line and column.
@ does nothing. Does not even exit copy mode.
copy_reg [key]
Store the current copybuffer contents in a register
referenced by key. If the name is omitted you will be
prompted to press the key.
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.
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.
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.
defflow on|off|auto [interrupt]
Same as the flow command except that the default setting for
new windows is changed. Initial setting is `auto'.
Specifying "defflow auto interrupt" is the same as the
command-line options -fa and -i.
deflogin on|off
Same as the login command except that the default setting
for new windows is changed. This is initialised with `on' as
distributed (see config.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'.
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 dependency 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.
defwrap on|off
Same as the wrap command except that the default setting for
new windows 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".
detach
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".)
dumptermcap
Write the termcap entry for the virtual terminal optimized
for 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.
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".
exec [[fdpat] newcommand [args ...]]
Run a subprocess (newcommand) in the current window. The
flow of data between newcommands stdin/stdout/stderr, the
process already running (shell) and screen itself (window)
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 already
running process. A colon (:) combines both. User input will
go to newcommand unless newcommand requests the old process'
output (fdpats first character is `!' or `:') or a pipe (|)
is added to the end of fdpat.
Invoking `exec' without arguments shows name and arguments
of the currently running subprocess in this window.
When a subprocess is running the `kill' command will affect
it instead of the windows process.
Refer to the postscript file `fdpat.ips' for illustration of
all 21 possible combinations. Each drawing shows the numbers
210 representing the three file descriptors of newcommand.
The box marked `W' is usual pty that has the old process
(shell) 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 omitted. A simple `|' is synonymous for the
pattern `!..|'; the word exec can be ommitted 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 orignal
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
Set the speed of the windows tty. If your stty command
operates on stdout, then add another `!'.
exec !..| less
|less
This adds a pager to the window output. The special
character `|' is needed to give the user control over the
pager although it gets its input from the original process.
!:sed -n s/.*Error.*/\007/p
Sends window output to both, the user and the sed command.
The sed inserts an additional bell character (oct. 007) to
the window output seen by screen. This will cause "Bell in
window x" messages, whenever the string "Error" appears in
the window.
flow [on|off|auto]
Sets the flow-control mode for this window. Without
parameters it cycles the current window's flow-control
setting from "automatic" to "on" to "off". 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. Default is set by `defflow'.
hardcopy
Writes out the currently displayed image to a file
hardcopy.n in the window's default directory, where n is the
number of the current window. This either appends or
overwrites the file if it exists. See below.
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. Default is `off'.
hardcopydir directory
Defines a directory where hardcopy files will be placed. If
unset hardcopys are dumped in screens current working
directory.
hardstatus [on|off]
Toggles the use of the terminal's 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 can only be used if the termcap/terminfo
capabilities "hs", "ts", "fs" and "ds" are set properly.
Default is `on' whenever the "hs" capability is present.
height [lines]
Set the display height to a specified number of lines. When
no argument is given it toggles between 24 and 42 lines
display.
help
Not really a online help, but displays a help screen showing
you all the key bindings. The first pages list all the
internal commands followed by their current 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 allow
you to execute commands even when the help screen is still
visible. See also "DEFAULT KEY BINDINGS" section.
history
Usually users work with a shell that allows easy access to
previous commands. For example 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).
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 the "time" command.
ins_reg [key]
Paste contents of register key in current windows input
stream. See also the "copy_reg" and "register" commands.
kill
Kill current window.
If there is an `exec' command running then it is killed.
Otherwise the process (shell) running in the window receives
a HANGUP condition, the window structure is removed and
screen switches to the previously displayed window. When
the last window is destroyed, screen exits. 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 to rebind kill to "C-a K".
lastmsg
Redisplay the last contents of the message/status line.
Useful if you're typing when a message appears, because the
message goes away when you press a key (unless your terminal
has a hardware status line). Refer to the commands
"msgwait" and "msgminwait" for fine tuning.
license
Display the disclaimer page. This is done whenever screen is
started without options, which should be often enough. See
also the "startup_message" command.
lockscreen
Lock this display. 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 $LOCKPRG (which must be set in the
shell from which screen is started) and is executed with the
user's uid and gid.
log [on|off]
Start/stop writing output of the current window to a file
"screenlog.n" in the window's default directory, where n is
the number of the current window. If no parameter is given,
the state of logging is toggled. The session log is appended
to the previous contents of the file if it already exists.
The current contents and the contents of the scrollback
history are not included in the session log. Default is
`off'.
logdir directory
Defines a directory where logfiles will be placed. If unset
logfiles are written in screens current working directory.
login [on|off]
Adds or removes the entry in the utmp database file for the
current window. This controls if the window is `logged in'.
When no parameter is given, the login state of the window is
toggled. Additionally to that toggle, it is convenient
having a `log in' and a `log out' key. E.g. `bind I login
on' and `bind O login off' will map these keys to be C-a I
and C-a O. The default setting (in config.h.in) should be
"on" for a screen that runs under suid-root. Use the
"deflogin" command to change the default login state for new
windows. Both commands are only present when screen has been
compiled with utmp support.
markkeys string
This is a method of changing the keymap used for
copy/history mode. The string is made up of oldchar=newchar
pairs which are separated by `:'. Example: The string
"B=^B:F=^F" will change the keys `C-b' and `C-f' to the vi
style binding (scroll up/down fill page). This happens to
be the default binding for `B' and `F'. The command
"markkeys h=^B:l=^F:$=^E" would set the mode for an emacs-
style binding.
meta
Insert the command character (C-a) in the current window's
input stream.
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 a new message when one
message is currently displayed. 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.
multiuser on|off
Switch between singleuser and multiuser mode. Standard
screen operation is singleuser. In multiuser mode the
commands `acladd' and `acldel' can be used to enable (and
disable) other users to access this screen.
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.
next
Switch to the next window. This command can be used
repeatedly to cycle through the list of windows.
number [n]
Change the current windows number. If the given number n is
already used by another window, both windows exchange their
numbers. If no argument is specified, the current window
number (and title) is shown.
obuflimit [limit]
If the output buffer contains more bytes than the specified
limit, no more data will be read from the windows. The
default value is 256. If you have a fast display (like
xterm), you can set it to some higher value. If no argument
is specified, the current setting is displayed.
other
Switch to the window displayed previously.
partial on|off
Defines whether the display should be refreshed (as done
with "C-a l") after switching to the current window. This
command only affects the current window. To affect all
windows use the allpartial command. Default is `off', of
course.
password [crypted_pw]
Present a crypted password in your ".screenrc" file and
screen will ask for it, whenever someone attempts to resume
a detached. This is useful if you have privileged programs
running under screen and you want to protect your session
from reattach attempts by another user masquerading as your
uid (i.e. any superuser.) If no crypted password is
specified, screen prompts twice for typing a password and
places its encryption in the copybuffer. Default is `none',
this disables password checking.
paste [registers]
Write the contents of the specified registers to the stdin
queue of the current window. The register '.' is treated as
the paste buffer. If no parameter is given only the paste
buffer is used. It can be filled with the copy, history and
readbuf commands.
pow_break
Reopen the window's terminal line and send a break
condition. See `break'.
pow_detach
Power detach. Mainly the same as detach, 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.
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.
prev
Switch to the window with the next lower number. This
command can be used repeatedly to cycle through the list of
windows.
process [key]
Stuff the contents of the specified register into screen's
input queue. If no argument is given you are prompted for a
register name. The text is parsed as if it had been typed in
from the users keyboard. This command can be used to bind
multiple actions to a single key.
quit
Kill all windows and terminate screen. Note that on vt100-
style terminals the keys C-4 and C-\ are identical. This
makes the default bindings dangerous: Be careful not to type
C-a C-4 when selecting window no. 4. Use the empty bind
command (as in "bind '^\'") to remove a key binding.
readbuf
Reads the contents of the current screen-exchange file into
the copy buffer. See also "bufferfile" command.
redisplay
Redisplay the current window. Needed to get a full redisplay
when in partial redraw mode.
register key string
Save the specified string to the register key. See also the
"ins_reg" command.
removebuf
Unlinks the screen-exchange file used by the commands
"writebuf" and "readbuf".
reset
Reset the virtual terminal to its "power-on" values. Useful
when strange settings (like scroll regions or graphics
character set) are left over from an application.
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 title "foobar" in window #2). Note,
that unlike previous versions of screen no additional
default window is created when "screen" commands are
included in your ".screenrc" file. When the initialization
is completed, screen switches to the last window specified
in your .screenrc file or, if none, opens a default window
#0.
scrollback num
Set the size of the scrollback buffer for the current
windows to num lines. The default scrollback is 100 lines.
See also the "defscrollback" command and use "C-a i" to view
the current setting.
select [n]
Switch to the window with the number n. If no window number
is specified, you get prompted for an identifier. This can
be title (alphanumeric window name) or a number. When a new
window is established, the first available number is
assigned to this window. Thus, the first window can be
activated by "select 0" (there can be no more than 10
windows present simultaneously unless screen is compiled
with a higher MAXWIN setting).
sessionname [name]
Rename the current session. Note, that for "screen -list"
the name shows up with the process-id prepended. If the
argument "name" is omitted, the name of this session is
displayed. Caution: The $STY environment variables still
reflects the old name. This may result in confusion. The
default is constructed from the tty and host names.
setenv [var [string]]
Set the environment variable var to value string. If only
var is specified, the user will be prompted to enter a
value. If no parameters are specified, the user will be
prompted for both variable and value. The environment is
inherited by all subsequently forked shells.
shell command
Set the command to be used to create a new shell. This
overrides the value of the environment variable $SHELL.
This is useful if you'd like to run a tty-enhancer which is
expecting to execute the program specified in $SHELL. If the
command begins with a '-' character, the shell will be
started as a login-shell.
shelltitle title
Set the title for all shells created during startup or by
the C-A C-c command. For details about what a title is, see
the discussion entitled "TITLES (naming windows)".
silence [on|off|sec]
Toggles silence monitoring of windows. When silence is
turned on and an affected window is switched into the
background, you will receive the silence notification
message in the status line after a specified period of
inactivity (silence). The default timeout can be changed
with the `silencewait' command or by specifying a number of
seconds instead of `on' or `off'. Silence is initially off
for all windows.
silencewait sec
Define the time that all windows monitored for silence
should wait before displaying a message. Default 30 seconds.
sleep num
This command will pause the execution of a .screenrc file
for num seconds. Keyboard activity will end the sleep. It
may be used to give users a chance to read the messages
output by "echo".
slowpaste usec
Define the speed at which text is inserted by the paste
("C-a ]") command. If the slowpaste value is nonzero text is
written character by character. screen will make a pause of
usec milliseconds after each write to allow the application
to process its input. Only use slowpaste if your underlying
system exposes flow control problems while pasting large
amounts of text.
startup_message on|off
Select whether you want to see the copyright notice during
startup. Default is `on', as you propably noticed.
suspend
Suspend screen. The windows are in the `detached' state,
while screen is suspended. This feature relies on the shell
being able to do job control.
term term
In each window's environment screen opens, the $TERM
variable is set to "screen" by default. But when no
description for "screen" is installed in the local termcap
or terminfo data base, you set $TERM to - say - "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 $SCREENCAP variable prior
to running screen. See the discussion on the "VIRTUAL
TERMINAL" in this manual, and the termcap(5) man page for
more information on termcap definitions.
time
Uses the message line to display the time of day, the host
name, and the load averages over 1, 5, and 15 minutes (if
this is available on your system). For window specific
information use "info".
title [windowalias]
Set the name of the current window to windowalias. If no
name is specified, screen prompts for one. This command was
known as `aka' in previous releases.
unsetenv var
Unset an environment variable.
vbell on|off
If your terminal does not support a visual bell, a `vbell-
message' is displayed in the status line. Sets the visual
bell setting for this window. If your terminal does not
support a visual bell, a `vbell-message' is displayed in the
status line. Refer to the termcap variable `vb' (terminfo:
'flash').
vbell_msg message
Sets the visual bell message. message is printed to the
status line if the window receives a bell character (^G) and
vbell is set to "on". The default message is "Wuff,
Wuff!!".
vbellwait sec
Define a delay in seconds after each display of screen's
visual bell message. The default is 1 second.
version
Print the current version and the compile date in the status
line.
wall message ...
Write a message to all displays. The message will appear in
the terminals status line.
width [num]
Toggle the window width between 80 and 132 columns or set it
to num columns if an argument is specified. This requires a
capable terminal and the termcap entries "Z0" and "Z1". See
the "termcap" command for more information.
windows
Uses the message line to display a list of all the windows.
Each window is listed by number with the name of process
that has been started in the window (or its title); the
current window is marked with a `*'; the previous window is
marked with a `-'; all the windows that are "logged in" are
marked with a `$'; 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)'; windows occupied by other users are marked with `&';
windows in the zombie state are marked with `Z'. If this
list is too long to fit on the terminals status line only
the portion around the current window is displayed.
wrap [on|off]
Sets the line-wrap setting for the current window. 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.
Default is `on'.
writebuf
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. The filename can be set with the bufferfile
command and defaults to "/tmp/screen-exchange".
writelock [on|off|auto]
In addition to access control lists, not all users may be
able to write to the same window at once. Per default,
writelock is in `auto' mode and grants exclusive input
permission to the user who is the first to switch to the
particular window. When he leaves the window, other users
may obtain the writelock (automatically). The writelock of
the current window is disabled by the command "writelock
off". If the user issues the command "writelock on" he keeps
the exclusive write permission while switching to other
windows.
xoff
xon
Insert a CTRL-s / CTRL-q character to the stdin queue of the
current window.
zombie [key]
Per default screen windows are removed from the window list
as soon as the windows process (e.g. shell) exits. When a
key is specified to the zombie command a `dead' windows will
remain in the list until it is selected and this key is
pressed or the "kill" command is issued.
THE MESSAGE LINE
Screen displays informational messages and other diagnostics
in a message line. While this line is distributed to appear
at the bottom of the screen, it can be defined to appear at
the top of the screen during compilation. If your terminal
has a status line defined in its termcap, screen will use
this for displaying its messages, otherwise a line of the
current 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 from window '$WINDOW'<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 "defflow" .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
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.
TITLES (naming windows)
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 title 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
"shelltitle" 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 title-string escape-sequence (<esc>kname<esc>\)
and the "title" 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
"title" 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 title 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 title-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 title. Once this is set up, screen will use the title-
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 nice-d
version of the "top" command in window 2 name "top" rather
than "nice".
shelltitle '> |csh'
screen 1
These commands would start a shell with the given
shelltitle. The title specified is an auto-title 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-
title name of "root:". For this auto-title 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 title
bind E title ""
bind u title (unknown)
The first binding doesn't have any arguments, so it would
prompt you for a title. when you type "C-a o". The second
binding would clear an auto-title's current setting (C-a E).
The third binding would set the current window's title to
"(unknown)" (C-a u).
One thing to keep in mind when adding a null title-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 bash
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 is 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 Z Send VT100 Identification String
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 ! Global 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
?1 (V) Application Cursor Keys
?3 (V) Change Terminal Width to 132
columns
?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)
ESC [ 8 ; Ph ; Pw t Resize the window to `Ph' lines
and `Pw' columns (SunView
special)
ESC [ c Send VT100 Identification String
ESC [ 6 n Send Cursor Position Report
SPECIAL TERMINAL CAPABILITIES
The following table describes all terminal capabilities that
are recognized by screen and are not in the termcap(5)
manual.
LP (bool) Terminal has vt100 style margins (`magic
margins'). Note that this capability is
obsolete because screen uses 'xn' instead.
Z0 (str) Change width to 132 columns.
Z1 (str) Change width to 80 columns.
WS (str) Resize display. This capability has the desired
width and height as arguments. SunView(tm)
example: '\E[8;%d;%dt'.
B8 (str) Tell screen to look out for characters with 8th
bit set. If such a character is found screen
processes the specified string and than outputs
the character with the 8th bit stripped off.
Note that the string can contain any esc-
sequences known to screen, too. (Example:
Single Shift G2 = \EN.)
OP (bool) Don't do a full vt100 style margin emulation.
Same as the -O option.
NF (bool) Terminal doesn't need flow control. Send ^S and
^Q direct to the application. Same as 'flow
off'. The opposite of this capability is 'xo'.
G0 (bool) Terminal can deal with ISO2022 font selection
sequences.
S0 (str) Switch charset 'G0' to the specified charset.
Default is '\E(%d'.
E0 (str) Switch charset 'G0' back to standard charset.
Default is '\E(B'.
C0 (str) Use the string as a conversion table for font
'0'. See the 'ac' capability for more details.
CS (str) Switch cursorkeys to application mode.
CE (str) Switch cursorkeys back to normal mode.
AN (bool) Turn on autonuke. See the 'autonuke' command
for more details.
OL (num) Set the output buffer limit. See the
'obuflimit' command for more details.
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.
COPYLEFT
Copyright (C) 1993 Juergen Weigert
(jnweiger@immd4.informatik.uni-erlangen.de) Michael
Schroeder (mlschroe@immd4.informatik.uni-erlangen.de)
Copyright (C) 1987 Oliver Laumann
This program is free software; you can redistribute it
and/or modify it under the terms of the GNU General Public
License as published by the Free Software Foundation; either
version 2, or (at your option) any later version.
This program is distributed in the hope that it will be
useful, but WITHOUT ANY WARRANTY; without even the implied
warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
PURPOSE. See the GNU General Public License for more
details.
You should have received a copy of the GNU General Public
License along with this program (see the file COPYING); if
not, write to the Free Software Foundation, Inc., 675 Mass
Ave, Cambridge, MA 02139, USA.
CONTRIBUTORS
Ken Beal (kbeal@amber.ssd.csd.harris.com),
Rudolf Koenig (rfkoenig@immd4.informatik.uni-erlangen.de),
Toerless Eckert (eckert@immd4.informatik.uni-erlangen.de),
Wayne Davison (davison@borland.com),
Patrick Wolfe (pat@kai.com, kailand!pat),
Bart Schaefer (schaefer@cse.ogi.edu),
Nathan Glasser (nathan@brokaw.lcs.mit.edu),
Larry W. Virden (lvirden@cas.org),
Howard Chu (hyc@hanauma.jpl.nasa.gov),
Tim MacKenzie (tym@dibbler.cs.monash.edu.au),
Markku Jarvinen (mta@{cc,cs,ee}.tut.fi),
Marc Boucher (marc@CAM.ORG),
Doug Siebert (dsiebert@isca.uiowa.edu),
Ken Stillson (stillson@tsfsrv.mitre.org),
Ian Frechett (frechett@spot.Colorado.EDU),
Brian Koehmstedt (bpk@gnu.ai.mit.edu),
Don Smith (djs6015@ultb.isc.rit.edu),
Frank van der Linden (vdlinden@fwi.uva.nl),
Martin Schweikert (schweik@cpp.ob.open.de),
David Vrona (dave@sashimi.lcu.com),
E. Tye McQueen (tye%spillman.UUCP@uunet.uu.net),
Matthew Green (phone@coombs.anu.edu.au),
Christopher Williams (cgw@unt.edu),
Matt Mosley (mattm@access.digex.net),
Gregory Neil Shapiro (gshapiro@wpi.WPI.EDU).
VERSION
This is version 3.5.1. Its 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) and `xs' are not handled correctly
(they are ignored). `xn' is treated as a magic-margin
indicator.
+ 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.
+ Screen may give a strange warning when your tty has no
utmp entry.
+ Send bugreports, fixes, enhancements, t-shirts, money,
beer & pizza to screen@uni-erlangen.de.