This is screen.info, produced by makeinfo version 4.0 from
./screen.texinfo.
START-INFO-DIR-ENTRY
* Screen: (screen). Full-screen window manager.
END-INFO-DIR-ENTRY
This file documents the `Screen' virtual terminal manager.
Copyright (c) 1993-1995 Free Software Foundation, Inc.
Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.
Permission is granted to copy and distribute modified versions of
this manual under the conditions for verbatim copying, provided that
the entire resulting derived work is distributed under the terms of a
permission notice identical to this one.
Permission is granted to copy and distribute translations of this
manual into another language, under the above conditions for modified
versions, except that this permission notice may be stated in a
translation approved by the Foundation.
File: screen.info, Node: Window Size, Next: Character Processing, Prev: Reset, Up: Virtual Terminal
Window Size
===========
- Command: width [`-w'|`-d'] [cols [lines]]
(`C-a W')
Toggle the window width between 80 and 132 columns, or set it to
COLS columns if an argument is specified. This requires a capable
terminal and the termcap entries `Z0' and `Z1'. See the `termcap'
command (*note Termcap::), for more information. You can also
specify a height if you want to change both values. The `-w'
option tells screen to leave the display size unchanged and just
set the window size, `-d' vice versa.
- Command: height [`-w'|`-d'] [lines [cols]]
(none)
Set the display height to a specified number of lines. When no
argument is given it toggles between 24 and 42 lines display.
File: screen.info, Node: Character Processing, Prev: Window Size, Up: Virtual Terminal
Character Processing
====================
- Command: c1 [state]
(none)
Change c1 code processing. `c1 on' tells screen to treat the input
characters between 128 and 159 as control functions. Such an
8-bit code is normally the same as ESC followed by the
corresponding 7-bit code. The default setting is to process c1
codes and can be changed with the `defc1' command. Users with
fonts that have usable characters in the c1 positions may want to
turn this off.
- Command: gr [state]
(none)
Turn GR charset switching on/off. Whenever screen sees an input
char with an 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 `defgr') is not to process GR switching because
otherwise the ISO88591 charset would not work.
- Command: bce [state]
(none)
Change background-color-erase setting. If `bce' is set to on, all
characters cleared by an erase/insert/scroll/clear operation will
be displayed in the current background color. Otherwise the
default background color is used.
- Command: kanji wtype [dtype]
(none)
Tell screen how to process kanji input/output. WTYPE and DTYPE
must be one of the strings `jis', `euc' or `sjis'. 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 `KJ'
termcap entry. *Note Special Capabilities::. See also `defkanji',
which changes the default setting of a new window.
- Command: charset set
(none)
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 `kanji' command is active.
The current setting can be viewed with the *Note Info:: command.
- Command: utf8 [state [dstate]]
(none)
Change the encoding used in the current window. If utf8 is
enabled, the strings sent to the window will be UTF-8 encoded and
vice versa. Omitting the parameter toggles the setting. If a
second parameter is given, the display's encoding is also changed
(this should rather be done with screen's `-U' option). See also
`defutf8', which changes the default setting of a new window.
- Command: defc1 state
(none)
Same as the `c1' command except that the default setting for new
windows is changed. Initial setting is `on'.
- Command: defgr state
(none)
Same as the `gr' command except that the default setting for new
windows is changed. Initial setting is `off'.
- Command: defbce state
(none)
Same as the `bce' command except that the default setting for new
windows is changed. Initial setting is `off'.
- Command: defkanji wtype
(none)
Same as the `kanji' command except that the default setting for
new windows is changed. Initial setting is `off', i.e. `jis'.
- Command: defcharset [set]
Like the `charset' command except that the default setting for new
windows is changed. Shows current default if called without
argument.
- Command: defutf8 state
(none)
Same as the `utf8' command except that the default setting for new
windows is changed. Initial setting is `on' if screen was started
with `-U', otherwise `off'.
File: screen.info, Node: Copy and Paste, Next: Subprocess Execution, Prev: Virtual Terminal, Up: Top
Copy and Paste
**************
For those confined to a hardware terminal, these commands provide a
cut and paste facility more powerful than those provided by most
windowing systems.
* Menu:
* Copy:: Copy from scrollback to buffer
* Paste:: Paste from buffer into window
* Registers:: Longer-term storage
* Screen-Exchange:: Sharing data between screen users
* History:: Recalling previous input
File: screen.info, Node: Copy, Next: Paste, Up: Copy and Paste
Copying
=======
- Command: copy
(`C-a [', `C-a C-[', `C-a <ESC>')
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, with controls as
outlined below.
* Menu:
* Line Termination:: End copied lines with CR/LF
* Scrollback:: Set the size of the scrollback buffer
* Copy Mode Keys:: Remap keys in copy mode
* Movement:: Move around in the scrollback buffer
* Marking:: Select the text you want
* Repeat count:: Repeat a command
* Searching:: Find the text you want
* Specials:: Other random keys
File: screen.info, Node: Line Termination, Next: Scrollback, Up: Copy
CR/LF
-----
- Command: crlf [state]
(none)
This affects the copying of text regions with the `C-a [' command.
If it is set to `on', lines will be separated by the two character
sequence `CR'/`LF'. Otherwise only `LF' is used. `crlf' is off
by default. When no parameter is given, the state is toggled.
File: screen.info, Node: Scrollback, Next: Copy Mode Keys, Prev: Line Termination, Up: Copy
Scrollback
----------
- Command: defscrollback num
(none)
Same as the `scrollback' command except that the default setting
for new windows is changed. Defaults to 100.
- Command: scrollback num
(none)
Set the size of the scrollback buffer for the current window to
NUM lines. The default scrollback is 100 lines. Use `C-a i' to
view the current setting.
- Command: compacthist [state]
(none)
This tells screen weather to suppress trailing blank lines when
scrolling up text into the history buffer. Turn compacting `on' to
hold more useful lines in your scrollback buffer.
File: screen.info, Node: Copy Mode Keys, Next: Movement, Prev: Scrollback, Up: Copy
markkeys
--------
- Command: markkeys string
(none)
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 command `markkeys h=^B:l=^F:$=^E'
would set some keys to be more familiar to `emacs' users. If your
terminal sends characters, that cause you to abort copy mode, then
this command may help by binding these characters to do nothing.
The no-op character is `a'nd is used like this: `markkeys @=L=H'
if you do not want to use the `H' or `L' commands any longer. As
shown in this example, multiple keys can be assigned to one
function in a single statement.
File: screen.info, Node: Movement, Next: Marking, Prev: Copy Mode Keys, Up: Copy
Movement Keys
-------------
`h', `j', `k', `l' move the cursor line by line or column by column.
`0', `^' and `$' move to the leftmost column or 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 `-' move the cursor to the leftmost column of the next or
previous line.
`G' moves to the specified absolute line (default: end of buffer).
`|' moves to the specified absolute column.
`w', `b', `e' move the cursor word by word.
`C-u' and `C-d' scroll the display up/down by the specified amount of
lines while preserving the cursor position. (Default: half screenfull).
`C-b' and `C-f' move the cursor up/down a full screen.
`g' moves to the beginning of the buffer.
`%' jumps to the specified percentage of the buffer.
Note that Emacs-style movement keys can be specified by a .screenrc
command. (`markkeys "h=^B:l=^F:$=^E"') There is no simple method for a
full emacs-style keymap, however, as this involves multi-character
codes.
File: screen.info, Node: Marking, Next: Repeat count, Prev: Movement, Up: Copy
Marking
-------
The copy range is specified by setting two marks. The text between
these marks will be highlighted. Press `space' to set the first or
second mark respectively.
`Y' and `y' can be used to mark one whole line or to mark from start of
line.
`W' marks exactly one word.
File: screen.info, Node: Repeat count, Next: Searching, Prev: Marking, Up: Copy
Repeat Count
------------
Any command in copy mode can be prefixed with a number (by pressing
digits `0...9') which is taken as a repeat count. Example: `C-a C-[ H
10 j 5 Y' will copy lines 11 to 15 into the paste buffer.
File: screen.info, Node: Searching, Next: Specials, Prev: Repeat count, Up: Copy
Searching
---------
`/' `vi'-like search forward.
`?' `vi'-like search backward.
`C-a s' `emacs' style incremental search forward.
`C-r' `emacs' style reverse i-search.
File: screen.info, Node: Specials, Prev: Searching, Up: Copy
Specials
--------
There are, however, some keys that act differently here from in
`vi'. `Vi' does not allow to yank rectangular blocks of text, but
`screen' does. Press
`c' or `C' to set the left or right margin respectively. If no repeat
count is given, both default to the current cursor position.
Example: Try this on a rather full text screen: `C-a [ M 20 l SPACE c
10 l 5 j C SPACE'.
This moves one to the middle line of the screen, moves in 20 columns
left, marks the beginning of the paste buffer, sets the left column,
moves 5 columns down, sets the right column, and then marks the end of
the paste buffer. Now try:
`C-a [ M 20 l SPACE 10 l 5 j SPACE'
and notice the difference in the amount of text copied.
`J' joins lines. It toggles between 4 modes: lines separated by a
newline character (012), lines glued seamless, lines separated by a
single space or comma separated lines. Note that you can prepend the
newline character with a carriage return character, by issuing a `set
crlf on'.
`v' is for all the `vi' users who use `:set numbers' - it toggles the
left margin between column 9 and 1.
`a' before the final space key turns on append mode. Thus the contents
of the paste buffer will not be overwritten, but appended to.
`A' turns on 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. *Note Screen-Exchange::.
This example demonstrates how to dump the whole scrollback buffer to
that file:
`C-a [ g SPACE G $ >'.
`C-g' gives information about the current line and column.
`x' exchanges the first mark and the current cursor position. You can
use this to adjust an already placed mark.
`@' does nothing. Absolutely nothing. Does not even exit copy mode.
All keys not described here exit copy mode.
File: screen.info, Node: Paste, Next: Registers, Prev: Copy, Up: Copy and Paste
Paste
=====
- Command: paste [registers [destination]]
(`C-a ]', `C-a C-]')
Write the (concatenated) contents of the specified registers to
the stdin stream of the current window. The register `.' is
treated as the paste buffer. If no parameter is specified the user
is prompted to enter a single register. 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 display's paste buffer is the destination.
Note, that `paste' uses a wide variety of resources: Usually both,
a current window and a current display are required. But 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.
- Command: pastefont [state]
Tell screen to include font information in the paste buffer. The
default is not to do so. This command is especially usefull for
multi character fonts like kanji.
- Command: slowpaste msec
- Command: defslowpaste msec
(none)
Define the speed text is inserted in the current window by the
`paste' command. If the slowpaste value is nonzero text is written
character by character. `screen' will pause for MSEC milliseconds
after each write to allow the application to process the input.
only use `slowpaste' if your underlying system exposes flow
control problems while pasting large amounts of text.
`defslowpaste' specifies the default for new windows.
- Command: readreg [register [filename]]
(none)
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
File: screen.info, Node: Registers, Next: Screen-Exchange, Prev: Paste, Up: Copy and Paste
Registers
=========
- Command: copy_reg [key]
(none)
Removed. Use `readreg' instead.
- Command: ins_reg [key]
(none)
Removed. Use `paste' instead.
- Command: process [key]
(none)
Stuff the contents of the specified register into the `screen'
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.
- Command: register key string
(none)
Save the specified STRING to the register KEY.
- Command: stuff string
(none)
Stuff the string STRING in the input buffer of the current window.
This is like the `paste' command, but with much less overhead.
You cannot paste large buffers with the `stuff' command. It is most
useful for key bindings. *Note Bindkey::.
File: screen.info, Node: Screen-Exchange, Next: History, Prev: Registers, Up: Copy and Paste
Screen-Exchange
===============
- Command: bufferfile [exchange-file]
(none)
Change the filename used for reading and writing with the paste
buffer. If the EXCHANGE-FILE parameter is omitted, `screen'
reverts to the default of `/tmp/screen-exchange'. 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
- Command: readbuf [filename]
(`C-a <')
Reads the contents of the specified file into the paste buffer.
If no file is specified, the screen-exchange filename is used.
- Command: removebuf
(`C-a =')
Unlinks the screen-exchange file.
- Command: writebuf [filename]
(`C-a >')
Writes the contents of the paste buffer to the specified file, or
the public accessible screen-exchange file if no filename is given.
This is thought of as a primitive means of communication between
`screen' users on the same host. See also `C-a <ESC>' (*note
Copy::).
File: screen.info, Node: History, Prev: Screen-Exchange, Up: Copy and Paste
History
=======
- Command: history
(`C-a {')
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' provides a primitive way of
recalling "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).
File: screen.info, Node: Subprocess Execution, Next: Key Binding, Prev: Copy and Paste, Up: Top
Subprocess Execution
********************
Control Input or Output of a window by another filter process. Use
with care!
* Menu:
* Exec:: The `exec' command syntax.
* Using Exec:: Weird things that filters can do.
File: screen.info, Node: Exec, Next: Using Exec, Up: Subprocess Execution
Exec
====
- Command: exec [[FDPAT] NEWCOMMAND [ARGS ... ]]
(none)
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 (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 to the end of FDPAT.
Invoking `exec' without arguments shows name and arguments of the
currently running subprocess in this window. Only one subprocess
can be running per window.
When a subprocess is running the `kill' command will affect it
instead of the windows process. Only one subprocess a time can be
running in each window.
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 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.
File: screen.info, Node: Using Exec, Prev: Exec, Up: Subprocess Execution
Using Exec
==========
Abbreviations:
* Whitespace between the word `exec' and FDPAT and the command name
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 when the `|' abbreviation is used.
* The word `exec' can always be replaced by leading `!'.
Examples:
`!/bin/sh'
`exec /bin/sh'
`exec ... /bin/sh'
All of the above are equivalent. 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'.
`!!stty 19200'
`exec!stty 19200'
`exec !.. stty 19200'
All of the above are equivalent. Set the speed of the window's
tty. If your stty command operates on stdout, then add another
`!'. This is a useful command, when a screen window is directly
connected to a serial line that needs to be configured.
`|less'
`exec !..| less'
Both are equivalent. 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.
`!: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.
File: screen.info, Node: Key Binding, Next: Flow Control, Prev: Subprocess Execution, Up: Top
Key Binding
***********
You may disagree with some of the default bindings (I know I do).
The `bind' command allows you to redefine them to suit your preferences.
* Menu:
* Bind:: `bind' syntax.
* Bind Examples:: Using `bind'.
* Command Character:: The character used to start keyboard commands.
* Help:: Show current key bindings.
* Bindkey:: `bindkey' syntax.
* Bindkey Examples:: Some easy examples.
* Bindkey Control:: How to control the bindkey mechanism.
File: screen.info, Node: Bind, Next: Bind Examples, Up: Key Binding
The `bind' command
==================
- Command: bind key [command [args]]
(none)
Bind a command to a key. 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 (*note Command Index::).
By default, most suitable commands are bound to one or more keys
(*note Default Key Bindings::; for instance, 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.
File: screen.info, Node: Bind Examples, Next: Command Character, Prev: Bind, Up: Key Binding
Examples of the `bind' command
==============================
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 <ESC> to the command that
creates an non-login window with title `root' in slot #9, with a
superuser shell and a scrollback buffer of 1000 lines.
File: screen.info, Node: Command Character, Next: Help, Prev: Bind Examples, Up: Key Binding
Command Character
=================
- Command: escape xy
(none)
Set the command character to X and the character generating a
literal command character (by triggering the `meta' command) to Y
(similar to the `-e' option). Each argument is either a single
character, a two-character sequence of the form `^x' (meaning
`C-x'), a backslash followed by an octal number (specifying the
ASCII code of the character), or a backslash followed by a second
character, such as `\^' or `\\'. The default is `^Aa', but ```'
is recommended by one of the authors.
- Command: defescape xy
(none)
Set the default command characters. This is equivalent to the
command `escape' except that it is useful for multiuser sessions
only. In a multiuser session `escape' changes the command
character of the calling user, where `defescape' changes the
default command characters for users that will be added later.
- Command: meta
(`C-a a')
Send the command character (`C-a') to the process in the current
window. The keystroke for this command is the second parameter to
the `-e' command line switch (*note Invoking Screen::), or the
`escape' .screenrc directive.
- Command: command
(none)
This command has the same effect as typing the screen escape
character (`C-a'). It is probably only useful for key bindings.
*Note Bindkey::.
File: screen.info, Node: Help, Next: Bindkey, Prev: Command Character, Up: Key Binding
Help
====
- Command: help
(`C-a ?')
Displays a help screen showing you all the key bindings. The first
pages list all the internal commands followed by their bindings.
Subsequent pages will display the custom commands, one command per
key. Press space when you're done reading each page, or return to
exit early. All other characters are ignored. *Note Default Key
Bindings::.
File: screen.info, Node: Bindkey, Next: Bindkey Examples, Prev: Help, Up: Key Binding
Bindkey
=======
- Command: bindkey [OPTS] [STRING [CMD ARGS]]
(none)
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 *Note Input Translation:: for
a list of default key bindings.
If the `-d' option is given, bindkey modifies the default table,
`-m' changes the copy mode table and with neither option the user
table is selected. The argument `string' is the sequence of
characters to which an action is bound. This can either be a fixed
tring 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.
File: screen.info, Node: Bindkey Examples, Next: Bindkey Control, Prev: Bindkey, Up: Key Binding
Bindkey Examples
================
Here are some examples of keyboard bindings:
bindkey -d
Show all of the default key bindings. The application mode entries are
marked with [A].
bindkey -k k1 select 1
Make the "F1" key switch to window one.
bindkey -t foo stuff barfoo
Make `foo' an abbreviation of the word `barfoo'. Timeout is disabled so
that users can type slowly.
bindkey "\024" mapdefault
This key-binding makes `C-t' an escape character for key-bindings. If
you did the above `stuff barfoo' binding, you can enter the word `foo'
by typing `C-t foo'. If you want to insert a `C-t' you have to press
the key twice (i.e. escape the escape binding).
bindkey -k F1 command
Make the F11 (not F1!) key an alternative screen escape (besides `C-a').
File: screen.info, Node: Bindkey Control, Prev: Bindkey Examples, Up: Key Binding
Bindkey Control
===============
- Command: mapdefault
(none)
Tell screen that the next input character should only be looked up
in the default bindkey table.
- Command: mapnotnext
(none)
Like mapdefault, but don't even look in the default bindkey table.
- Command: maptimeout timo
(none)
Set the intercharacter timer for input sequence detection to a
timeout of TIMO ms. The default timeout is 300ms. Maptimeout with
no arguments shows the current setting.
File: screen.info, Node: Flow Control, Next: Termcap, Prev: Key Binding, Up: Top
Flow Control
************
`screen' can trap flow control characters or pass them to the
program, as you see fit. This is useful when your terminal wants to use
XON/XOFF flow control and you are running a program which wants to use
^S/^Q for other purposes (i.e. `emacs').
* Menu:
* Flow Control Summary:: The effect of `screen' flow control
* Flow:: Setting the flow control behavior
* XON/XOFF:: Sending XON or XOFF to the window
File: screen.info, Node: Flow Control Summary, Next: Flow, Up: Flow Control
About `screen' flow control settings
====================================
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' command. By default the windows are set
to automatic flow-switching. It can then be toggled between the three
states 'fixed on', 'fixed off' and 'automatic' interactively with the
`flow' command bound to `C-a f'.
The automatic flow-switching mode deals with flow control using the
TIOCPKT mode (like `rlogin' does). If the tty driver does not support
TIOCPKT, screen tries to determine 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 the `interrupt'
parameter only takes effect when flow-control is enabled. If your
program's output is interrupted by mistake, 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.
File: screen.info, Node: Flow, Next: XON/XOFF, Prev: Flow Control Summary, Up: Flow Control
Flow
====
- Command: defflow fstate [interrupt]
(none)
Same as the `flow' command except that the default setting for new
windows is changed. Initial setting is `auto'. Specifying `flow
auto interrupt' has the same effect as the command-line options
`-fa' and `-i'. Note that if `interrupt' is enabled, all existing
displays are changed immediately to forward interrupt signals.
- Command: flow [fstate]
(`C-a f', `C-a C-f')
Sets the flow-control mode for this window to FSTATE, which can be
`on', `off' or `auto'. Without parameters it cycles the current
window's flow-control setting. Default is set by `defflow'.
File: screen.info, Node: XON/XOFF, Prev: Flow, Up: Flow Control
XON and XOFF
============
- Command: xon
(`C-a q', `C-a C-q')
Send a ^Q (ASCII XON) to the program in the current window.
Redundant if flow control is set to `off' or `auto'.
- Command: xoff
(`C-a s', `C-a C-s')
Send a ^S (ASCII XOFF) to the program in the current window.
File: screen.info, Node: Termcap, Next: Message Line, Prev: Flow Control, Up: Top
Termcap
*******
`screen' demands the most out of your terminal so that it can
perform its VT100 emulation most efficiently. These functions provide
means for tweaking the termcap entries for both your physical terminal
and the one simulated by `screen'.
* Menu:
* Window Termcap:: Choosing a termcap entry for the window.
* Dump Termcap:: Write out a termcap entry for the window.
* Termcap Syntax:: The `termcap' and `terminfo' commands.
* Termcap Examples:: Uses for `termcap'.
* Special Capabilities:: Non-standard capabilities used by `screen'.
* Autonuke:: Flush unseen output
* Obuflimit:: Allow pending output when reading more
* Character Translation:: Emulating fonts and charsets.
File: screen.info, Node: Window Termcap, Next: Dump Termcap, Up: Termcap
Choosing the termcap entry for a window
=======================================
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.
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 `$TERMCAP' value used by `screen' by
using the `termcap' command, or by defining the variable `$SCREENCAP'
prior to startup. When the latter defined, its value will be copied
verbatim into each window's `$TERMCAP' variable. This can either be
the full terminal definition, or a filename where the terminal `screen'
(and/or `screen-w') is defined.
Note that `screen' honors the `terminfo' command if the system uses
the terminfo database rather than termcap. On such machines the
`$TERMCAP' variable has no effect and you must use the `dumptermcap'
command (*note Dump Termcap::) and the `tic' program to generate
terminfo entries for `screen' windows.
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. The `info' command displays a line starting with `PRIN'
while the printer is active.
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
`$TERMCAP' cannot be modified by parent processes. You can force
`screen' to include all capabilities in `$TERMCAP' with the `-a'
command-line option (*note Invoking Screen::).
File: screen.info, Node: Dump Termcap, Next: Termcap Syntax, Prev: Window Termcap, Up: Termcap
Write out the window's termcap entry
====================================
- Command: dumptermcap
(`C-a .')
Write the termcap entry for the virtual terminal optimized for the
currently active window to the file `.termcap' in the user's
`$HOME/.screen' directory (or wherever `screen' stores its
sockets. *note Files::). This termcap entry is identical to the
value of the environment variable `$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'.
File: screen.info, Node: Termcap Syntax, Next: Termcap Examples, Prev: Dump Termcap, Up: Termcap
The `termcap' command
=====================
- Command: termcap term terminal-tweaks [window-tweaks]
- Command: terminfo term terminal-tweaks [window-tweaks]
- Command: termcapinfo term terminal-tweaks [window-tweaks]
(none)
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. You have to place these commands in
one of the screenrc startup files, as they are meaningless once
the terminal emulator is booted.
If your system uses the terminfo database rather than termcap,
`screen' will understand the `terminfo' command, which has the
same effects as the `termcap' command. Two separate commands are
provided, as there are subtle syntactic differences, e.g. when
parameter interpolation (using `%') is required. Note that the
termcap names of the capabilities should also be used with the
`terminfo' command.
In many cases, where the arguments are valid in both terminfo and
termcap syntax, you can use the command `termcapinfo', which is
just a shorthand for a pair of `termcap' and `terminfo' commands
with identical arguments.
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
(*note Virtual Terminal::).
File: screen.info, Node: Termcap Examples, Next: Special Capabilities, Prev: Termcap Syntax, Up: Termcap
Termcap Examples
================
Some examples:
termcap xterm* xn: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
(xn), but they don't really have a status line (no 'hs' - append `@' to
turn entries off). Note that we assume `xn' for all terminal names
that start with `vt', but only if you don't specify a termcap command
for that terminal.
termcap vt* xn
termcap vt102|vt220 Z0=\E[?3h:Z1=\E[?3l
Specifies the firm-margined `xn' 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'.
*Note Virtual Terminal::, for the details of the `screen' terminal
emulation. *Note Termcap: (termcap)Top, for more information on
termcap definitions.
File: screen.info, Node: Special Capabilities, Next: Autonuke, Prev: Termcap Examples, Up: Termcap
Special Terminal Capabilities
=============================
The following table describes all terminal capabilities that are
recognized by `screen' and are not in the termcap manual (*note
Termcap: (termcap)Top.). You can place these capabilities in your
termcap entries (in `/etc/termcap') or use them with the commands
`termcap', `terminfo' and `termcapinfo' in your `screenrc' files. It is
often not possible to place these capabilities in the terminfo database.
`LP'
(bool)
Terminal has VT100 style margins (`magic margins'). Note that this
capability is obsolete -- `screen' now uses the standard `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'.
`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 `nx'.
`G0'
(bool)
Terminal can deal with ISO 2022 font selection sequences.
`S0'
(str)
Switch charset `G0' to the specified charset. Default is `\E(%.'.
`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 cursor-keys to application mode.
`CE'
(str)
Switch cursor-keys to cursor mode.
`AN'
(bool)
Enable autonuke for displays of this terminal type. (*note
Autonuke::).
`OL'
(num)
Set the output buffer limit. See the `obuflimit' command (*note
Obuflimit::) for more details.
`KJ'
(str)
Set the kanji type of the terminal. Valid strings are `jis', `euc'
and `sjis'.
`AF'
(str)
Change character foreground color in an ANSI conform way. This
capability will almost always be set to `\E[3%dm' (`\E[3%p1%dm' on
terminfo machines).
`AB'
(str)
Same as `AF', but change background color.
`AX'
(bool)
Does understand ANSI set default fg/bg color (`\E[39m / \E[49m').
`XC'
(str)
Describe a translation of characters to strings depending on the
current font. (*note Character Translation::).
`XT'
(bool)
Terminal understands special xterm sequences (OSC, mouse tracking).
`TF'
(bool)
Add missing capabilities to the termcap/info entry. (Set by
default).
File: screen.info, Node: Autonuke, Next: Obuflimit, Prev: Special Capabilities, Up: Termcap
Autonuke
========
- Command: autonuke STATE
(none)
Sets whether a clear screen sequence should nuke all the output
that has not been written to the terminal. *Note Obuflimit::.
This property is set per display, not per window.
- Command: defautonuke STATE
(none)
Same as the `autonuke' command except that the default setting for
new displays is also changed. Initial setting is `off'. Note that
you can use the special `AN' terminal capability if you want to
have a terminal type dependent setting.
File: screen.info, Node: Obuflimit, Next: Character Translation, Prev: Autonuke, Up: Termcap
Obuflimit
=========
- Command: obuflimit [LIMIT]
(none)
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. This property is set per display, not per
window.
- Command: defobuflimit LIMIT
(none)
Same as the `obuflimit' command except that the default setting
for new displays is also changed. Initial setting is 256 bytes.
Note that you can use the special `OL' terminal capability if you
want to have a terminal type dependent limit.