Several MM variables change the way messages are displayed on your screen, including when to clear the screen, and how the more screen pager works.
The screen display is also greatly affected by system settings outside MM, particularly the terminal type you entered during login, and any key remapping you did with Kermit or with the stty command. Check with your local systems staff if your screen looks wrong or if keys don't seem to function right.
The program more is very widely used to display output on a terminal screen. All it does, basically, is show one screen of text at a time. Its name comes from the prompt --more-- that appears at the bottom of the screen. The basic responses are the space bar to see more, and q to quit (not see the rest).
Message 22 (79 chars) Received: by cunixf.cc.columbia.edu (5.54/5.10) id AA12719; Fri, 30 Nov 90 15:53:45 EDT Date: Fri, 30 Nov 1990 15:43:45 EDT From: Joe Brennan <firstname.lastname@example.org> To: jb51 Subject: Text of this chapter Message-Id: <CMM.email@example.com> Several MM variables change the way messages are displayed on your screen, including when to clear the screen, and how the "more" screen pager works. The screen display is also greatly affected by system settings outside MM, particularly the terminal type you entered during login, and any key remapping you did with Kermit or with the "stty" command. Check with a consultant if your screen looks wrong or if keys don't seem to function right. THE SCREEN PAGER, MORE The program "more" is very widely used to display output on a terminal --More-- [Press space to continue, 'q' to quit.]
In MM, the variable crt-filter determines what screen pager to use when displaying messages. Normally it tells MM to use more, in one of two versions. The variable use-crt-filter-always determines whether to use the screen pager when the message is shorter than one screen, for consistency.
/usr/ucb/more -d is the default for crt-filter, the more command with option -d. When there is more of the message after what is on the screen, it shows the prompt --more--, and the option -d makes it add to that the helpful message [Press space to continue, 'q' to quit.]. When it reaches the end of the message, the next MM prompt (MM> or R>) appears after the end of the message.
/usr/ucb/more.mm -x is a special version of more modified to go with MM. It is the same as more -d except that when it reaches the end of the message, it shows a special prompt, [Press any key to continue]. After you press any key, you see the next MM prompt. The reason for more.mm is that the combination of regular more and the two-line novice prompt might push a line of text off the top of the screen. As a further touch, since more.mm -x puts up a prompt at the end of the message, it makes some sense to set use-crt-filter-always to yes, so that it will always be used, even for short messages that wouldn't get a regular more prompt.
You may want to set crt-filter to nothing (i.e. set crt-filter followed by nothing) for some purposes. In that case, when you read a message, the display will not stop until the end of the message, so if it is longer than a screen, the beginning will disappear off the top of the screen. Some communications programs let you redirect output from your screen to your printer, so if for example you want to print what you get from a read command, you might like to prevent the pauses and --more-- prompts.
Note that you can use more outside MM for many purposes. At the UNIX shell prompt, more with a filename shows you what is in that file, one screen at a time. When output from a command would run off the screen, add |more to pipe the output through more, so that it is shown one screen at a time (like finger |more).
You can clear the screen at any point in MM with the command blank. After you give a blank command, everything on your screen is cleared off and the MM prompt and cursor appear in the upper left corner.
MM clears the screen by itself when it starts up and when it displays a new message for you to read. The variable clear-screen, normally set to yes, controls that screen clearing. You can change it by typing set clear-screen no, and then save-init, and the screen will not clear.
The browse command, which you can use to read mail, displays a prompt for each message, something like what the headers command shows, before displaying the message itself. The screen clear before the prompt is controlled by another variable, browse-clear-screen, normally set to yes, while the screen clear before the message itself is as usual controlled by clear-screen.
Control-l also clears the screen, so it's the same as blank if you just type it at an MM prompt. If you type a command, and then control-l, what it does is different depending on the variable control-l-confirm, normally set to no. At that setting, it clears the screen and puts the command line you just typed at the top of the screen. If you change the variable to yes (set control-l-confirm yes), then control-l will clear the screen and then immediately execute the command. To see the effect, try typing a command, like headers all and then control-l, changing the variable back and forth. When you have it the way you like it, use save-init to save the setting.