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SCREEN (1)

screen manager with VT100/ANSI terminal emulation

SYNOPSIS

screen

-\fIoptions\fP

\fIcmd\fP

\fIargs\fP

screen -r

DESCRIPTION

Screen

When screen is called, it creates a single window with a shell in it (or the specified command) and then gets out of your way so that you can use the program as you normally would. Then, at any time, you can create new (full-screen) windows with other programs in them (including more shells), kill existing windows, view a list of 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. All windows run their programs completely independent of each other. Programs continue to run when their window is currently not visible 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 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.

Screen does not understand the prefix \*QC-\*U to mean control. Please use the caret notation (\*Q^A\*U instead of \*QC-a\*U) 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 \*QC-a c\*U. 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 \*QC-a :\*U command line) and then using it just like the \*QC-a c\*U command. In addition, new windows can be created by running a command like:

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 \*Q/etc/utmp\*U 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 \*Qtalk\*U, \*Qscript\*U, \*Qshutdown\*U, \*Qrsend\*U, \*Qsccs\*U 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 \*QC-a L\*U.

GETTING STARTED

screen

tset

If you're impatient and want to get started without doing a lot more reading, you should remember this one command: \*QC-a ?\*U. Typing these two characters will display a list of the available screen commands and their bindings. Each keystroke is discussed in the section \*QDEFAULT KEY BINDINGS\*U. The manual section \*QCUSTOMIZATION\*U deals with the contents of your .screenrc.

If your terminal is a \*Qtrue\*U auto-margin terminal (it doesn't allow the last position on the screen to be updated without scrolling the screen) consider to use 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 \*Qmagic\*U 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 \*Qtrue\*U 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

-a

screen

-A

screen

-c file

-d | -D [ \fIpid.tty.host ]

screen ,

screen

screen 's

-D

-r

-R

-d -r

-d -R

-d -RR

-D -r

-D -R

-D -RR

-e xy

screen

-f\fP , -fn , and -fa

-h num

-i

-l and -ln

-ls and -list

screen ,

pid.tty.host

screen

-r

-wipe

-L

screen

-m

screen

-m -d

screen

-m -D

-O

-q

-r [ \fIpid.tty.host ]

-r \fIsessionowner/[ \fIpid.tty.host ]

screen

-d

-D

screen

-R

screen

-R

screen

-d

-D

-s

-S sessionname

-t name

-v

-wipe [ \fImatch ]

-r

-x

screen

DEFAULT KEY BINDINGS

screen

The following table shows the default key bindings:

-e]x

screen

screen's

screen

C-a n

screen .

C-a <

screen

CUSTOMIZATION

screen

When screen is invoked, it executes initialization commands from the files \*Q/etc/screenrc\*U and \*Q.screenrc\*U in the user's home directory. These are the \*Qprogrammer's defaults\*U 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 $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 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 '\e' if no variable substitution shall be performed. A string in single-quotes is also protected from variable substitution.

Two configuration files are shipped as examples with your screen distribution: \*Qetc/screenrc\*U and \*Qetc/etcscreenrc\*U. They contain a number of useful examples for various commands.

Customization can also be done 'on-line'. To enter the command mode type `C-a :'. Note that commands starting with \*Qdef\*U change default values, while others change current settings.

The following commands are available: 3 acladd usernames [ crypted-pw ] addacl usernames

Enable users to fully access this screen session. Usernames can be one user or a comma separated list of users. This command enables to attach to the screen session and performs the equivalent of `aclchg usernames +rwx "#?"'. executed. To add a user with restricted access, use the `aclchg' command below. If an optional second parameter is supplied, it should be a crypted password for the named user(s). `Addacl' is a synonym to `acladd'. Multi user mode only. 3 aclchg usernames permbits list chacl usernames permbits list

Change permissions for a comma separated list of users. Permission bits are represented as `r', `w' and `x'. Prefixing `+' grants the permission, `-' removes it. The third parameter is a comma separated list of commands and/or windows (specified either by number or title). The special list `#' refers to all windows, `?' to all commands. if usernames consists of a single `*', all known users are affected. A command can be executed when the user has the `x' bit for it. The user can type input to a window when he has its `w' bit set and no other user obtains a writelock for this window. Other bits are currently ignored. To withdraw the writelock from another user in window 2: `aclchg username -w+w 2'. To allow read-only access to the session: `aclchg username -w "#"'. As soon as a user's name is known to screen he can attach to the session and (per default) has full permissions for all command and windows. Execution permission for the acl commands, `at' and others should also be removed or the user may be able to regain write permission. Rights of the special username nobody cannot be changed (see the \*Qsu\*U command). `Chacl' is a synonym to `aclchg'. Multi user mode only. 3 acldel username

Remove a user from screen 's access control list. If currently attached, all the user's displays are detached from the session. He cannot attach again. Multi user mode only. 3 aclgrp username [ groupname ]

Creates groups of users that share common access rights. The name of the group is the username of the group leader. Each member of the group inherits the permissions that are granted to the group leader. That means, if a user fails an access check, another check is made for the group leader. A user is removed from all groups the special value \*Qnone\*U is used for groupname . If the second parameter is omitted all groups the user is in are listed. 3 aclumask [[ users ] +bits |[ users ] -bits .... ] umask [[ users ] +bits |[ users ] -bits .... ]

This specifies the access other users have to windows that will be created by the caller of the command. Users may be no, one or a comma separated list of known usernames. If no users are specified, a list of all currently known users is assumed. Bits is any combination of access control bits allowed defined with the \*Qaclchg\*U command. The special username \*Q?\*U predefines the access that not yet known users will be granted to any window initially. The special username \*Q??\*U predefines the access that not yet known users are granted to any command. Rights of the special username nobody cannot be changed (see the \*Qsu\*U command). `Umask' is a synonym to `aclumask'. 3 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 \*Qactivity\*U command. Each occurrence of `%' in message is replaced by the number of the window in which activity has occurred, and each occurrence of `^G' is replaced by the definition for bell in your termcap (usually an audible bell). The default message is 'Activity in window %n' Note that monitoring is off for all windows by default, but can be altered by use of the \*Qmonitor\*U command (C-a M). 3 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 \*Qallpartial off\*U. This is a global flag that immediately takes effect on all windows overriding the \*Qpartial\*U settings. It does not change the default redraw behavior of newly created windows. 3 at [\fIidentifier\fP][ #\fP|\fP*\fP|\fP%\fP] command [ args ... ]

Execute a command at other displays or windows as if it had been entered there. \*QAt\*U 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 omitted from the identifier. If identifier has a `#' or nothing appended it is matched against window numbers and titles. Omitting an identifier in front of the `#', `*' or `%'-character selects all users, displays or windows because a prefix-match is performed. Note that on the affected display(s) a short message will describe what happened. Permission is checked for initiator of the \*Qat\*U command, not for the owners of the affected display(s). Note that the '#' character works as a comment introducer when it is preceded by whitespace. This can be escaped by prefixing a '\e'. Permission is checked for the initiator of the \*Qat\*U command, not for the owners of the affected display(s). Caveat: When matching against windows, the command is executed at least once per window. Commands that change the internal arrangement of windows (like \*Qother\*U) may be called again. In shared windows the command will be repeated for each attached display. Beware, when issuing toggle commands like \*Qlogin\*U! Some commands (e.g. \*Qstuff\*U, \*Qprocess\*U or \*Qpaste\*U) require that a display is associated with the target windows. These commands may not work correctly under \*Qat\*U looping over windows. 3 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. 3 autofixterm on | off

Sets whether screen will add missing capabilities to the termcap/info entry. It is on by default. 3 autonuke on | off

Sets whether a clear screen sequence should nuke all the output that has not been written to the terminal. See also \*Qobuflimit\*U. 3 bell_msg [ message ]

When a bell character is sent to a background window, screen displays a notification in the message line. The notification message can be re-defined by this command. Each occurrence of `%' in message is replaced by the number of the window to which a bell has been sent, and each occurrence of `^G' is replaced by the definition for bell in your termcap (usually an audible bell). The default message is 'Bell in window %n' An empty message can be supplied to the \*Qbell_msg\*U command to suppress output of a message line (bell_msg ""). Without parameter, the current message is shown. 3 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 \*QDEFAULT KEY BINDINGS\*U section, e.\|g. the command to create a new window is bound to \*QC-c\*U and \*Qc\*U. The \*Qbind\*U 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 \*Q^x\*U (meaning \*QC-x\*U), a backslash followed by an octal number (specifying the ASCII code of the character), or a backslash followed by a second character, such as \*Q\e^\*U or \*Q\e\e\*U. 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 ^k
        bind k
        bind K kill
        bind ^f screen telnet foobar
        bind \e033 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 \*QC-a C-w\*U would also be available as \*QC-a space\*U). The next three lines remove the default kill binding from \*QC-a C-k\*U and \*QC-a k\*U. \*QC-a K\*U is then bound to the kill command. Then it binds \*QC-f\*U to the command \*Qcreate a window with a TELNET connection to foobar\*U, and bind \*Qescape\*U to the command that creates an non-login window with a.\|k.\|a. \*Qroot\*U in slot #9, with a superuser shell and a scrollback buffer of 1000 lines. 3 bindkey [ -d ] [ -m ] [ -a ] [[ -k | -t ] string [ cmd args ]]

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

        bindkey -d

        bindkey -k k1 select 1

        bindkey -t foo stuff barfoo

        bindkey "\e024" mapdefault

        bindkey -k F1 command

break

[ duration ]

Send a break signal for duration*0.25 seconds to this window. For non-Posix systems the time interval may be rounded up to full seconds. Most useful if a character device is attached to the window rather than a shell process (See also chapter \*QWINDOW TYPES\*U). The maximum duration of a break signal is limited to 15 seconds. 3 breaktype [ tcsendbreak | TIOCSBRK | TCSBRK ]

Choose one of the available methods of generating a break signal for terminal devices. This command should affect the current window only. But it still behaves identical to \*Qdefbreaktype\*U. This will be changed in the future. Calling \*Qbreaktype\*U with no parameter displays the break method for the current window. 3 bufferfile [ exchange-file ]

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

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

c1 [ on | off ]

Change c1 code processing. \*QC1 on\*U tells screen to treat the input characters between 128 and 159 as control functions. Such an 8-bit code is normally the same as ESC followed by the corresponding 7-bit code. The default setting is to process c1 codes and can be changed with the \*Qdefc1\*U command. Users with fonts that have usable characters in the c1 positions may want to turn this off. 3 caption always | splitonly [ string ] caption string [ string ]

This command controls the display of the window captions. Normally a caption is only used if more than one window is shown on the display (split screen mode). But if the type is set to always screen shows a caption even if only one window is displayed. The default is splitonly . The second form changes the text used for the caption. You can use all escapes from the \*QSTRING ESCAPES\*U chapter. Screen uses a default of `%3n %t'. You can mix both forms by providing a string as an additional argument. 3 charset set

Change the current character set slot designation and charset mapping. The first four character of set are treated as charset designators while the fifth and sixth character must be in range '0' to '3' and set the GL/GR charset mapping. On every position a '.' may be used to indicate that the corresponding charset/mapping should not be changed (set is padded to six characters internally by appending '.' chars). New windows have "BBBB02" as default charset, unless a \*Qkanji\*U command is active. The current setting can be viewed with the \*Qinfo\*U command. 3 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 \*Qscreen\*U command from within \*Q.screenrc\*U or by means of \*QC-a : screen ...\*U or \*QC-a c\*U 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. 3 clear

Clears the current window and saves its image to the scrollback buffer. 3 colon [ prefix ]

Allows you to enter \*Q.screenrc\*U command lines. Useful for on-the-fly modification of key bindings, specific window creation and changing settings. Note that the \*Qset\*U 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 \*QC-a esc\*U (copy mode) as its `Vi command mode'. 3 command

This command has the same effect as typing the screen escape character (^A). It is probably only useful for key bindings. See also \*Qbindkey\*U. 3 compacthist [ on | off ]

This tells screen weather to suppress trailing blank lines when scrolling up text into the history buffer. 3 console [ on | off ]

Grabs or un-grabs the machines console output to a window. Note : Only the owner of /dev/console can grab the console output. This command is only available if the machine supports the ioctl TIOCCONS. 3 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 : +4n

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: \*QC-a C-[ H 10 j 5 Y\*U will copy lines 11 to 15 into the paste buffer.

Searching :

/ Vi-like search forward.

? Vi-like search backward.

C-a s Emacs style incremental search forward.

C-r Emacs style reverse i-search.

Specials : There are however some keys that act differently than in vi . Vi does not allow one to yank rectangular blocks of text, but screen does. Press

c or C to set the left or right margin respectively. If no repeat count is given, both default to the current cursor position. Example: Try this on a rather full text screen: \*QC-a [ M 20 l SPACE c 10 l 5 j C SPACE\*U.

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

and notice the difference in the amount of text copied.

J joins lines. It toggles between 4 modes: lines separated by a newline character (012), lines glued seamless, lines separated by a single whitespace and comma separated lines. Note that you can prepend the newline character with a carriage return character, by issuing a \*Qcrlf on\*U.

v is for all the vi users with \*Q:set numbers\*U - 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 paste buffer will not be overwritten, but is appended to.

A toggles in append mode and sets a (second) mark.

> sets the (second) mark and writes the contents of the paste buffer to the screen-exchange file (/tmp/screen-exchange per default) once copy-mode is finished. This example demonstrates how to dump the whole scrollback buffer to that file: \*QC-A [ g SPACE G $ >\*U.

C-g gives information about the current line and column.

x exchanges the first mark and the current cursor position. You can use this to adjust an already placed mark.

@ does nothing. Does not even exit copy mode.

All keys not described here exit copy mode. -4n 3 copy_reg [ key ]

No longer exists, use \*Qreadreg\*U instead. 3 crlf [ on | off ]

This affects the copying of text regions with the `C-a [' command. If it is set to `on', lines will be separated by the two character sequence `CR' - `LF'. Otherwise (default) only `LF' is used. When no parameter is given, the state is toggled. 3 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 \*QSCREEN\*U process correctly. Debug output from attacher processes can only be turned off once and forever. 3 defc1 on | off

Same as the c1 command except that the default setting for new windows is changed. Initial setting is `on'. 3 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. 3 defbreaktype [ tcsendbreak | TIOCSBRK | TCSBRK ]

Choose one of the available methods of generating a break signal for terminal devices. The preferred methods are tcsendbreak and TIOCSBRK . The third, TCSBRK , blocks the complete screen session for the duration of the break, but it may be the only way to generate long breaks. Tcsendbreak and TIOCSBRK may or may not produce long breaks with spikes (e.g. 4 per second). This is not only system dependant, this also differs between serial board drivers. Calling \*Qdefbreaktype\*U with no parameter displays the current setting. 3 defcharset [ \fIset ]

Like the charset command except that the default setting for new windows is changed. Shows current default if called without argument. 3 defescape xy

Set the default command characters. This is equivalent to the \*Qescape\*U except that it is useful multiuser sessions only. In a multiuser session \*Qescape\*U changes the command character of the calling user, where \*Qdefescape\*U changes the default command characters for users that will be added later. 3 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 \*Qdefflow auto interrupt\*U is the same as the command-line options -fa and -i . 3 defgr on | off

Same as the gr command except that the default setting for new windows is changed. Initial setting is `off'. 3 defhstatus [ \fIstatus ]

The hardstatus line that all new windows will get is set to status\fR. This command is useful to make the hardstatus of every window display the window number or title or the like. Status may contain the same directives as in the window messages, but the directive escape character is '^E' (octal 005) instead of '%'. This was done to make a misinterpretation of program generated hardstatus lines impossible. If the parameter status is omitted, the current default string is displayed. Per default the hardstatus line of new windows is empty. 3 defkanji jis | sjis | euc

Same as the kanji command except that the default setting for new windows is changed. Initial setting is `off', i.e. `jis'. 3 deflogin on | off

Same as the login command except that the default setting for new windows is changed. This is initialized with `on' as distributed (see config.h.in). 3 defmode mode

The mode of each newly allocated pseudo-tty is set to mode. Mode is an octal number. When no \*Qdefmode\*U command is given, mode 0622 is used. 3 defmonitor on | off

Same as the monitor command except that the default setting for new windows is changed. Initial setting is `off'. 3 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. 3 defscrollback num

Same as the scrollback command except that the default setting for new windows is changed. Initial setting is 100. 3 defshell command

Synonym to the shell command. See there. 3 defsilence on | off

Same as the silence command except that the default setting for new windows is changed. Initial setting is `off'. 3 defslowpaste msec"

Same as the slowpaste command except that the default setting for new windows is changed. Initial setting is 0 milliseconds, meaning `off'. 3 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 \*Qwrap\*U command (\*QC-a r\*U) or by means of "C-a : wrap on|off". 3 defwritelock on | off | auto

Same as the writelock command except that the default setting for new windows is changed. Initially writelocks will off. 3 defzombie [\fIkeys\fP]

Synonym to the zombie command. Both currently change the default. See there. 3 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 \*QCOMMAND-LINE OPTIONS\*U.) 3 displays

Shows a tabular listing of all currently connected user front-ends (displays). This is most useful for multiuser sessions. 3 digraph [ \fIpreset ]

This command prompts the user for a digraph sequence. The next two characters typed are looked up in a builtin table and the resulting character is inserted in the input stream. For example, if the user enters 'a"', an a-umlaut will be inserted. If the first character entered is a 0 (zero), screen will treat the following characters (up to three) as an octal number instead. The optional argument preset is treated as user input, thus one can create an \*Qumlaut\*U key. For example the command "bindkey ^K digraph '"'" enables the user to generate an a-umlaut by typing CTRL-K a. 3 dumptermcap

Write the termcap entry for the virtual terminal optimized for the currently active window to the file \*Q.termcap\*U in the user's \*Q$HOME/.screen\*U directory (or wherever screen stores its sockets. See the \*QFILES\*U 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 . 3 echo [ -n ] message

The echo command may be used to annoy screen users with a 'message of the day'. Typically installed in a global /etc/screenrc. The option \*Q-n\*U may be used to suppress the line feed. See also \*Qsleep\*U. Echo is also useful for online checking of environment variables. 3 escape xy

Set the command character to x and the character generating a literal command character (by triggering the \*Qmeta\*U command) to y (similar to the -e option). Each argument is either a single character, a two-character sequence of the form \*Q^x\*U (meaning \*QC-x\*U), a backslash followed by an octal number (specifying the ASCII code of the character), or a backslash followed by a second character, such as \*Q\e^\*U or \*Q\e\e\*U. The default is \*Q^Aa\*U. 3 exec [[ fdpat ] newcommand [ args ... ]]

Run a unix subprocess (specified by an executable path newcommand and its optional arguments) in the current window. The flow of data between newcommands stdin/stdout/stderr, the process originally started in the window (let us call it "application-process") and screen itself (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 application-process. A colon (:) combines both. User input will go to newcommand unless newcommand receives the application-process' output (fdpats first character is `!' or `:') or a pipe symbol (|) is added (as a fourth character) to the end of fdpat. Invoking `exec' without arguments shows name and arguments of the currently running subprocess in this window. Only one subprocess a time can be running in each window. When a subprocess is running the `kill' command will affect it instead of the windows process. Refer to the postscript file `doc/fdpat.ps' for a confusing illustration of all 21 possible combinations. Each drawing shows the digits 2,1,0 representing the three file descriptors of newcommand. The box marked `W' is the usual pty that has the application-process on its slave side. The box marked `P' is the secondary pty that now has screen at its master side. Abbreviations: Whitespace between the word `exec' and fdpat and the command can be omitted. Trailing dots and a fdpat consisting only of dots can be omitted. A simple `|' is synonymous for the pattern `!..|'; the word exec can be omitted here and can always be replaced by `!'. Examples:

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

Set the speed of the window's tty. If your stty command operates on stdout, then add another `!'.

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 window's process. This works, because less listens on stderr (a behavior that screen would not expect without the `|') when its stdin is not a tty. Less versions newer than 177 fail miserably here; good old pg still works.

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. 3 fit

Change the window size to the size of the current region. This command is needed because screen doesn't adapt the window size automatically if the window is displayed more than once. 3 flow [ on | off | auto\fR]\fP

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 \*QFLOW-CONTROL\*U later on in this document for full details and note, that this is subject to change in future releases. Default is set by `defflow'. 3 focus

Move the input focus to the next region. This is done in a cyclic way so that the top region is selected after the bottom one. 3 gr [ on | off ]

Turn GR charset switching on/off. Whenever screen sees an input character with the 8th bit set, it will use the charset stored in the GR slot and print the character with the 8th bit stripped. The default (see also \*Qdefgr\*U) is not to process GR switching because otherwise the ISO88591 charset would not work. 3 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. 3 hardcopy_append on | off

If set to "on", screen will append to the "hardcopy.n" files created by the command \*QC-a h\*U, otherwise these files are overwritten each time. Default is `off'. 3 hardcopydir directory

Defines a directory where hardcopy files will be placed. If unset, hardcopys are dumped in screen 's current working directory. 3 hardstatus [ on | off ] hardstatus \fR[\fBalways\fR]\fBlastline | message | ignore [ string ] hardstatus string [ string ]

This command configures the use and emulation of the terminal's hardstatus line. The first form toggles whether screen will use the hardware status line to display messages. If the flag is set to `off', these messages are overlaid in reverse video mode at the display line. The default setting is `on'. The second form tells screen what to do if the terminal doesn't have a hardstatus line (i.e. the termcap/terminfo capabilities "hs", "ts", "fs" and "ds" are not set). If the type \*Qlastline\*U is used, screen will reserve the last line of the display for the hardstatus. \*Qmessage\*U uses screen's message mechanism and \*Qignore\*U tells screen never to display the hardstatus. If you prepend the word \*Qalways\*U to the type, screen will use the type even if the terminal supports a hardstatus. The third form specifies the contents of the hardstatus line. '%h' is used as default string, i.e. the stored hardstatus of the current window (settable via \\E]0;^G or \\E_\\\\) is displayed. You can customize this to any string you like including the escapes from the \*QSTRING ESCAPES\*U chapter. If you leave out the argument string , the current string is displayed. You can mix the second and third form by providing the string as additional argument. 3 height [ \fIlines\fP ]

Set the display height to a specified number of lines. When no argument is given it toggles between 24 and 42 lines display. 3 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. See also \*QDEFAULT KEY BINDINGS\*U section. 3 history

Usually users work with a shell that allows easy access to previous commands. For example csh has the command \*Q!!\*U to repeat the last command executed. Screen allows you to have a primitive way of re-calling \*Qthe command that started ...\*U: 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). 3 hstatus status

Change the window's hardstatus line to the string status. 3 info

Uses the message line to display some information about the current window: the cursor position in the form \*Q(column,row)\*U starting with \*Q(1,1)\*U, the terminal width and height plus the size of the scrollback buffer in lines, like in \*Q(80,24)+50\*U, the current state of window XON/XOFF flow control is shown like this (See also section FLOW CONTROL):

  +flow     automatic flow control, currently on.
  -flow     automatic flow control, currently off.
  +(+)flow  flow control enabled. Agrees with automatic control.
  -(+)flow  flow control disabled. Disagrees with automatic control.
  +(-)flow  flow control enabled. Disagrees with automatic control.
  -(-)flow  flow control disabled. Agrees with automatic control.

The current line wrap setting (`+wrap' indicates enabled, `-wrap' not) is also shown. The flags `ins', `org', `app', `log', `mon' or `nored' are displayed when the window is in insert mode, origin mode, application-keypad mode, has output logging, insert mode, origin mode, application-keypad mode, output logging, activity monitoring or partial redraw enabled.

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 is shown.

Additional modes depending on the type of the window are displayed at the end of the status line (See also chapter \*QWINDOW TYPES\*U). If the state machine of the terminal emulator is in a non-default state, the info line is started with a string identifying the current state. For system information use the \*Qtime\*U command. 3 ins_reg [ \fIkey ]

No longer exists, use \*Qpaste\*U instead. 3 kanji jis | euc | sjis [ jis | euc | sjis\fR]

Tell screen how to process kanji input/output. The first argument sets the kanji type of the current window. Each window can emulate a different type. The optional second parameter tells screen how to write the kanji codes to the connected terminal. The preferred method of setting the display type is to use the \*QKJ\*U termcap entry. See also \*Qdefkanji\*U, which changes the default setting of a new window. 3 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 (your display) switches to another window. When the last window is destroyed, screen exits. After a kill screen switches to the previously displayed window. Note: Emacs users should keep this command in mind, when killing a line. It is recommended not to use \*QC-a\*U as the screen escape key or to rebind kill to \*QC-a K\*U. 3 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 \*Qmsgwait\*U and \*Qmsgminwait\*U for fine tuning. 3 license

Display the disclaimer page. This is done whenever screen is started without options, which should be often enough. See also the \*Qstartup_message\*U command. 3 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. Warning: When you leave other shells unlocked and you have no password set on screen , the lock is void: One could easily re-attach from an unlocked shell. This feature should rather be called `lockterminal'. 3 log [ on | off ]

Start/stop writing output of the current window to a file \*Qscreenlog.n\*U in the window's default directory, where n is the number of the current window. This filename can be changed with the `logfile' command. 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'. 3 logfile filename logfile flush secs

Defines the name the logfiles will get. The default is \*Qscreenlog.%n\*U. The second form changes the number of seconds screen will wait before flushing the logfile buffer to the file-system. The default value is 10 seconds. 3 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 \*Qon\*U for a screen that runs under suid-root. Use the \*Qdeflogin\*U command to change the default login state for new windows. Both commands are only present when screen has been compiled with utmp support. 3 logtstamp [ on | off ] logtstamp after [ secs ] logtstamp string [ string ]

This command controls logfile time-stamp mechanism of screen. If time-stamps are turned \*Qon\*U, screen adds a string containing the current time to the logfile after two minutes of inactivity. When output continues and more than another two minutes have passed, a second time-stamp is added to document the restart of the output. You can change this timeout with the second form of the command. The third form is used for customizing the time-stamp string (`-- %n:%t -- time-stamp -- %M/%d/%y %c:%s --\\n' by default). 3 mapdefault

Tell screen that the next input character should only be looked up in the default bindkey table. See also \*Qbindkey\*U. 3 mapnotnext

Like mapdefault, but don't even look in the default bindkey table. 3 maptimeout [ timo ]

Set the inter-character timer for input sequence detection to a timeout of timo ms. The default timeout is 300ms. Maptimeout with no arguments shows the current setting. See also \*Qbindkey\*U. 3 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 \*QB=^B:F=^F\*U 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 \*Qmarkkeys h=^B:l=^F:$=^E\*U would set the mode for an emacs-style binding. If your terminal sends characters, that cause you to abort copy mode, then this command may help by binding these characters to do nothing. The no-op character is `@' and is used like this: \*Qmarkkeys @=L=H\*U if you do not want to use the `H' or `L' commands any longer. As shown in this example, multiple keys can be assigned to one function in a single statement. 3 meta

Insert the command character (C-a) in the current window's input stream. 3 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. 3 msgminwait sec

Defines the time screen delays a new message when one message is currently displayed. The default is 1 second. 3 msgwait sec

Defines the time a message is displayed if screen is not disturbed by other activity. The default is 5 seconds. 3 multiuser on | off

Switch between singleuser and multiuser mode. Standard screen operation is singleuser. In multiuser mode the commands `acladd', `aclchg', `aclgrp' and `acldel' can be used to enable (and disable) other users accessing this screen session. 3 nethack on | off

Changes the kind of error messages used by screen . When you are familiar with the game \*Qnethack\*U, 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. 3 next

Switch to the next window. This command can be used repeatedly to cycle through the list of windows. 3 nonblock [ on | off ]

Enable or disable flow control for the current user interface (display). It is used to prevent a slow display from slowing down the processing of data output by a window. This command may be helpful when multiple displays show the same window. Nonblock is initially off for all displays. 3 number [ \fIn ]

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. 3 obuflimit [ \fIlimit ]

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. 3 only

Kill all regions but the current one. 3 other

Switch to the window displayed previously. If this window does no longer exist, other has the same effect as next. 3 partial on | off

Defines whether the display should be refreshed (as with redisplay) after switching to the current window. This command only affects the current window. To immediately affect all windows use the allpartial command. Default is `off', of course. This default is fixed, as there is currently no defpartial command. 3 password [ \fIcrypted_pw ]

Present a crypted password in your \*Q.screenrc\*U 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 paste buffer. Default is `none', this disables password checking. 3 paste [ registers [ dest_reg ]]

Write the (concatenated) 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 the user is prompted for a single register to paste. The paste buffer can be filled with the copy, history and readbuf commands. Other registers can be filled with the register, readreg and paste commands. If paste is called with a second argument, the contents of the specified registers is pasted into the named destination register rather than the window. If '.' is used as the second argument, the displays paste buffer is the destination. Note, that \*Qpaste\*U uses a wide variety of resources: Whenever a second argument is specified no current window is needed. When the source specification only contains registers (not the paste buffer) then there need not be a current display (terminal attached), as the registers are a global resource. The paste buffer exists once for every user. 3 pastefont [ on | off ]

Tell screen to include font information in the paste buffer. The default is not to do so. This command is especially useful for multi character fonts like kanji. 3 pow_break

Reopen the window's terminal line and send a break condition. See `break'. 3 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. 3 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. Without parameter, the current message is shown. 3 prev

Switch to the window with the next lower number. This command can be used repeatedly to cycle through the list of windows. 3 printcmd [ cmd ]

If cmd is not an empty string, screen will not use the terminal capabilities \*Qpo/pf\*U if it detects an ansi print sequence ESC [ 5 i but pipe the output into cmd . This should normally be a command like \*Qlpr\*U or \*Q'cat > /tmp/scrprint'\*U. printcmd without a command displays the current setting. The ansi sequence ESC \e ends printing and closes the pipe. Warning: Be careful with this command! If other user have write access to your terminal, they will be able to fire off print commands. 3 process [ \fIkey ]

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 user's keyboard. This command can be used to bind multiple actions to a single key. 3 quit

Kill all windows and terminate screen . Note that on VT100-style terminals the keys C-4 and C-\e 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 \*Qbind '^\e'\*U) to remove a key binding. 3 readbuf

Reads the contents of the current screen-exchange file into the paste buffer. See also \*Qbufferfile\*U command. 3 readreg [ register [ filename ]]

Does one of two things, dependent on number of arguments: with zero or one arguments it it duplicates the paste buffer contents into the register specified or entered at the prompt. With two arguments it reads the contents of the named file into the register, just as readbuf reads the screen-exchange file into the paste buffer. The following example will paste the system's password file into the screen window (using register p, where a copy remains):

        C-a : readreg p /etc/passwd
        C-a : paste p

redisplay

Redisplay the current window. Needed to get a full redisplay when in partial redraw mode. 3 register key string

Save the specified string to the register key. See also the \*Qpaste\*U command. 3 remove

Kill the current region. This is a no-op if there is only one region. 3 removebuf

Unlinks the screen-exchange file used by the commands \*Qwritebuf\*U and \*Qreadbuf\*U. 3 reset

Reset the virtual terminal to its \*Qpower-on\*U values. Useful when strange settings (like scroll regions or graphics character set) are left over from an application. 3 screen \fP[\fI-opts\fP] [\fIn\fP] [\fIcmd\fP [\fIargs\fP]]

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>), the all-capability-flag (-a) and scrollback option (-h <num>) may be specified with each command. The option (-M) turns monitoring on for this window. The option (-L) turns output logging on for this window. 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 \*Qscreen\*U, this command (with the given arguments) is started in the window; otherwise, a shell is created. Thus, if your \*Q.screenrc\*U contains the lines

        # example for .screenrc:
        screen 1
        screen -fn -t foobar -L 2 telnet foobar

screen

scrollback \fP\fInum\fP

Set the size of the scrollback buffer for the current windows to num lines. The default scrollback is 100 lines. See also the \*Qdefscrollback\*U command and use \*QC-a i\*U to view the current setting. 3 select [ \fIWindowID ]

Switch to the window identified by WindowID. This can be a prefix of a window title (alphanumeric window name) or a window number. The parameter is optional and if omitted, you get prompted for an identifier. When a new window is established, the first available number is assigned to this window. Thus, the first window can be activated by \*Qselect 0\*U. The number of windows is limited at compile-time by the MAXWIN configuration parameter. sessionname [ \fIname ]

Rename the current session. Note, that for \*Qscreen -list\*U the name shows up with the process-id prepended. If the argument \*Qname\*U 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. 3 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. 3 shell \fIcommand\fP

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. 3 shelltitle \fItitle\fP

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 \*QTITLES (naming windows)\*U. 3 silence [ on | off |\fIsec\fP]

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. 3 silencewait sec

Define the time that all windows monitored for silence should wait before displaying a message. Default 30 seconds. sleep \fP\fInum\fP

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 \*Qecho\*U. 3 slowpaste \fImsec\fP

Define the speed at which text is inserted into the current window by the paste ("C-a ]") command. If the slowpaste value is nonzero text is written character by character. screen will make a pause of msec milliseconds after each single character 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. 3 sorendition [ \fIattr\fR [ \fIcolor ]]

Change the way screen does highlighting for text marking and printing messages. Attr is a hexadecimal number and describes the attributes (inverse, underline, ...) the text will get. Color is a 2 digit number and changes the foreground/background of the highlighted text. Some knowledge of screen 's internal character representation is needed to make the characters appear in the desired way. The default is currently 10 99 (standout, default colors). 3 split

Split the current region into two new ones. All regions on the display are resized to make room for the new region. The blank window is displayed on the new region. 3 startup_message on\fP|\fBoff

Select whether you want to see the copyright notice during startup. Default is `on', as you probably noticed. 3 stuff string

Stuff the string string in the input buffer of the current window. This is like the \*Qpaste\*U command but with much less overhead. You cannot paste large buffers with the \*Qstuff\*U command. It is most useful for key bindings. See also \*Qbindkey\*U. 3 su [ username [ password [ password2 ]]

Substitute the user of a display. The command prompts for all parameters that are omitted. If passwords are specified as parameters, they have to be specified un-crypted. The first password is matched against the systems passwd database, the second password is matched against the screen password as set with the commands \*Qacladd\*U or \*Qpassword\*U. \*QSu\*U may be useful for the screen administrator to test multiuser setups.