The commands in this section include things that allow screen to communicate information to the user (like the info command) and things that change how screen looks (like the caption command).

The information-providing commands are pretty simple: C-a i gives some information about the current window; C-a t displays some information about the system on which screen is running (including the current time); C-a m redisplays the last message that screen displayed (in case you missed it); C-a v displays information about the version of screen that's running; and C-a , displays the license information screen that is shown at screen startup by default.

Some terminals, mostly hardware serial terminals, have a separate area of their display that is reserved as a status line. Many modern graphical terminals use the titlebar of the window for such status information. screen calls this a “hardstatus line”. When screen starts, it checks to see if the hs termcap capability is set; if so, it assumes that there's a hardstatus line present. If there's a hardstatus line and the hardstatus option is set to “on” (which is the default setting), screen will use the hardstatus line to display status messages.

screen also advertises the hardstatus capability to programs running in its windows. When a program uses the hardstatus escape sequence (ESC_stringESC\) or the xterm title escape sequence (ESC]0;string^G), screen stores that string on a per-window basis. The per-window hardstatus string can also be changed with the hstatus command (and the default hstatus for new windows can be set with defhstatus).

The hardstatus command can also be used to set a string that will be displayed in the hardstatus line when screen isn't using it to display messages. The string can contain any of screen's string escapes. The default value is %h, which just displays the current window's hstatus string.

One of the most common things that screen users want to do is to have some sort of status bar at the bottom (or top) of the display. screen provides several ways to do this.

If your terminal has a hardstatus line (as discussed above), you can use the hardstatus string as a status bar. If you don't have a hardstatus line, you have two choices. The first is to use the command hardstatus lastline, which tells screen to reserve the last line of the display for use as a hardstatus line. With a hardstatus string param command, you will get a status bar at the bottom of your display.

The second option is to use the caption command. When the display is split into multiple regions (see Region Management for more details), screen puts a caption at the bottom of each region. You can use the caption always command to always display the caption, even if the display is not split. Just as with hardstatus, there's a caption string param command that can be used to make a status bar. It uses all the same string escapes that the hardstatus command does.

There are tradeoffs for each of the two approaches. One big one is that it's common to (ab)use the hardstatus capability to put things into ''xterm'''s title bar. If you plan to do that, you'll need to use the caption for your status bar. Another tradeoff is that you might want different information available in the captions for split displays than in your main status bar. In that case, you'd want to use the hardstatus line for the status bar.

screen can either use an audible bell or a visual bell, as controlled by the vbell command. If vbell is off, when screen receives an ASCII BEL character in the current window, it sends a bell character (usually an ASCII BEL, but it depends on what the terminal's termcap says) to the display (which will, presumably, beep). If vbell is on, when screen receives a BEL character, it either triggers the display terminal's visual bell, if the terminal's termcap has a vb capability, or it flashes the screen and displays the vbell_msg. C-a C-g will toggle vbell on and off.

If screen receives a bell in a window other than the current one, it displays the bell_msg onscreen.

A screen window does not have to be the same size as the display that's connected to it, although screen will resize windows to the display when you switch to them. This only applies to the first display showing the window; if another connected display, either from the -x command-line option or from a multiuser session, switches to an already-displayed window, the window keeps the size set by the first display.

The height command can change either the height or the height and width of a window. (If you want to just change the width, use the width command, which is exactly like height with the arguments reversed.) If the display's termcap supports it, screen will change both the display terminal's and the current window's dimensions. You can specify changing just the display or just the window with the -d and -w options, respectively.

If a window's dimensions have gotten out of sync with a display's, you can use the C-a F command to resize the window to the display.

• -A - Disables one aspect of screen's default behavior: Normally, if the terminal can be resized, then screen will resize the terminal to fit the dimensions of the windows it's displaying. When -A is given, resizable terminals work just like nonresizable terminals–the windows are resized to fit the dimensions of the display. (See below for Windows PuTTY)

• C-a C - (clear) Clears the current window.
• C-a F - (fit) Fits the current window to the display's dimensions.
• C-a C-g - (vbell) Toggles visual bell mode.
• C-a i - (info) Displays information about the current window.
• C-a m - (lastmsg) Redisplays the last message for this display.
• C-a t - (time) Displays system information.
• C-a v - (version) Displays screen's version information.
• C-a W - (width) Toggles the display between 80 and 132 columns.
• C-a , - (license) Displays screen's license information.

• attrcolor - Remaps the effect of text attributes.
• autonuke - Determines whether a given window will attempt to display buffered text after a clear command is received.
• bell_msg - Changes the message printed when a bell character is received in another window.
• caption - Controls the display of the caption line at the bottom of screen windows.
• clear - Clears the current window, but puts its text into the scrollback buffer.
• defautonuke - Changes the default autonuke setting for new windows.
• defhstatus - Sets the default hardstatus line for new windows.
• echo - Displays a message on the current display as if it were a screen message.
• fit - Resizes the window to fit the current display region.
• height - Changes the dimensions of the window or the display.
• info - Display information about screen and the current window in the message area.
• license - Displays screen's license, as happens when screen starts up.
• nethack - Controls the use of nethack-themed messages from screen.
• hardstatus - Controls use of the terminal's hardstatus line (if any) for displaying screen messages.
• hstatus - Synonym for hardstatus string status.
• lastmsg - Redisplays the last message that screen showed on the current display.
• msgminwait - Sets the minimum length of time that a screen message will be visible even if the user interacts with screen.
• msgwait - Sets the length of time that a message will remain visible if the user does not interact with screen during the lifetime of the message.
• sorendition - Defines the visual appearance of screen's messages.
• startup_message - Enables or disables the display of screen's license information when screen starts up.
• time - Displays (or controls the display of) system information.
• vbell - Sets or toggles the visual bell.
• vbell_msg - Sets or displays the message displayed for visual bells.
• vbellwait - Defines a hysteresis for visual bells.
• version - Uses the message area to display screen's version and compile date.
• wall - Like echo, but sends the message to all displays, with the name of the current user prepended.
• width - Like height, but with the order of arguments reversed.

You can force the status line to always stay at the bottom of the screen and set up a statusline string that displays the window information by adding either of these to your .screenrc:

hardstatus alwayslastline "%w"

caption always "%w"

This puts the current window in bold and surrounded by brackets:

caption always "%{-b ..}%-w%{+b ..}[[%n%f*%t]]%{-}%+w"

See the examples in truncation/padding escapes, particularly the last example.

This small snippet for your .screenrc uses both the caption and hardstatus line to give a two-line statusbar at the bottom of the display. The upper line (the caption line) consists of the number and name of all open windows, black on white background, with the active window centered and highlighted. The lower line (the hardstatus line) shows the window number, window name and the window's hardstatus in white on black.

hardstatus alwayslastline "%= %3n %t%? [%h]%? %="
caption always "%= %-w%L>%{= BW}%n*%t%{-}%52<%+w %L="

In this section, we'll build up a configuration that uses the xterm title bar as a hardstatus line and displays a status bar at the bottom of the screen.

To start with, we'll tell screen that xterms (and some other terminals that use the same escape sequences) do have a hardstatus line, and we'll use the escape sequences for setting the title bar as the hardstatus escape sequences:

termcapinfo xterm*|Eterm|mlterm "hs:ts=\E]0;:fs=\007:ds=\E]0;screen\007"

Title bars aren't good places for actual status messages, so we'll tell screen not to use the hardstatus line for status messages (they'll be displayed at the bottom of the screen, just as if there was no hardstatus line):

hardstatus off

We'll set the hardstatus string to show us the number and title of the current window, as well as the window's hstatus string. Because of the %? escapes, the brackets are only shown if the window has an hstatus string:

hardstatus string "screen %n (%t)%? [%h]%?"

Finally, we have the caption that makes for our status bar at the bottom of the screen. It makes use of the %F escape to change the colors depending on whether it's attached to the window with the focus. This causes the currently-focused window to stand out.

If the caption is on a non-focused window, the entire bar is blue text on a blue background (so it just looks blue), with the exception of the window's information, which is blue on yellow. The focused (or only) window's caption has a blue-on-cyan information section with the date and computer name, followed by the window list in white on blue. The current window is centered in the window list and is displayed in blue on yellow:

caption always "%?%F%{-b bc}%:%{-b bb}%?%C|%D|%M %d|%H%?%F%{+u wb}%? %L=%-Lw%45>%{+b by}%n%f*%t%{-}%+Lw%-0<"

With GNU screen 2009-05-15 (git://git.savannah.gnu.org/screen.git :: 9cdf8e20), the resize disable command line option -A does not work with PuTTY on Windows (0.60). One way to work around this is to disable the terminal feature for remote-controlled terminal resizing in PuTTY. This setting is found in “Terminal” > “Features” > “Disable remote-controlled terminal resizing”. After this you do not need to specify -A since screen will now force a resizing.

The same problem occurs with iTerm 2 on Mac OS X, and the solution is approximately the same: in your profile, select the terminal tab, then mark the checkbox Disable session-initiated window resizing.