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| Newer page: | version 2 | Last edited on Monday, October 25, 2004 4:06:54 am | by StuartYeates | |
| Older page: | version 1 | Last edited on Friday, June 7, 2002 1:07:48 am | by perry | Revert |
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-
-
-Visible bell mini-Howto
-
-
-
-----
-
-!!!Visible bell mini-Howto
-
-!!Alessandro Rubini, rubini@linux.itv2.3, 2001-12-03
-
-
-----
-''This document explains how to use termcap to configure a visual bell
-on one's system and describes how to disable audible bells on demand.''
-----
-
-
-
-
-!!1. Copyright and License
-
-
-
-
-!!2. Introduction
-
-
-
-
-!!3. Spekearectomy
-
-
-
-
-!!4. Per-console Beep Configuration
-
-
-
-
-!!5. Basic Concepts About Termcap and Terminfo
-
-
-
-
-!!6. Defining a Visible Bell
-
-
-
-
-!!7. Disabling the Audible Bell on the Text Console
-
-
-
-
-!!8. Telling Applications to Avoid Beeping
-
-
-
-
-!!9. The Dark Side of the Problem
-----
-
-!!1. Copyright and License
-
-
-This document is Copyright (c) 1997, Alessandro Rubini.
-
-
-This document is distributed under the terms of the GNU Free Documentation License.
-You should have received a copy along with it. If not, it is available from
-http://www.fsf.org/licenses/fdl.html.
-
-
-
-----
-
-!!2. Introduction
-
-
-The Linux console driver beeps the audible bell whenever a BEL char is
-output (ASCII code 7). Though this is a right choice for the default
-behaviour, many users don't like their computer to beep. This
-mini-Howto is meant to explain how to tell applications not to output
-the BEL code. It also explain how to instruct the kernel and the X
-Window System to avoid beeping when a BEL is output. Note that most of
-this document refers to the text console, as configuring the X server
-is an easy catch-all for any user who works in a graphic environment.
-
-
-In my opinion the best way to face a fussy computer is fixing the
-hardware, and my own computer doesn't even carry a loudspeaker.
-
-
-
-----
-
-!!3. Spekearectomy
-
-
-Speakerectomy is by far the most brilliant solution to the audible bell
-problem. As its name implies, it consists in removing the beeps by removing
-the beeper. The operation is straightforward and you don't
-even need any anesthetic, but if you want there's room for refinement.
-
-
-PC's are usually equipped with a silly switch to lower CPU clock. The
-switch is never used when you work in a multitasking environment, as
-you don't even need to slow the computer down to run games based on
-software loops. Unfortunately we can't use the switch to increase
-processor speed, but we can use it to enable/disable the
-loudspeaker. Sometimes the speaker is useful even if you enjoy a
-silent number cruncher, for example to signal the end of a lenghty
-compilation. To modify the switch functionality, just detatch it from
-the main board and connect its wires in series with the
-loudspeaker.
-
-
-Owners of laptop boxes, unfortunately, don't have easy access to the
-loudspeaker, and neither they have a spare switch to turn to a
-different task. The preferred solution for such users is configuring
-their software to avoid beeping, as described below.
-
-
-
-----
-
-!!4. Per-console Beep Configuration
-
-
-As of Linux 1.3.43, Martin Mares added the ability to configure the
-pitch and duration of the beep, by modifying console.c. Each
-console can be configured to feature a different duration and/or pitch
-of the bell sound; the task is accomplished by using escape sequences
-to the console device. You can configure your own ~/.profile
-or ~/.login file to select a different beep sound associated
-to each console (or no beep at all, if needed).
-
-
-The escape sequences work as follow:
-
-
-*ESC-
[[10;xx
] selects the bell frequency in Hertz. The value
-should be in the range 21-32766, otherwise the result is undefined.
-If the `xx' argument is missing, the default value (750Hz) will apply,
-as in `ESC-[[10].
-*
-
-*ESC-[[11;xx] selects the bell duration, in milli-seconds.
-If you specify more than 2 seconds, the default applies (125ms). Once
-again, if the `xx' argument is missing (ESC-[[11]) the default value
-will be used.
-*
-
-
-
-To select, for example, a 50Hz pitch for one-second duration, you can
-"echo -e "\\33[[10;50]\\33[[11;1000]"" with bash (where "-e"
-means `understand Escape sequences'. If you use tcsh the same
-command spells "echo "\\033[[10;50]\\033[[11;1000]"".
-
-
-Although I don't know of any version of the setterm command that
-supports such configuration, a future version of the command might
-well support a command-line option to configure the bell sound.
-
-
-If you run Linux-1.3.43 or newer, you may be satisfied with the escape
-sequences and avoid reading further. If you run an older kernel, or if
-you want the visual bell, you'll enjoy the rest of this document.
-
-
-
-----
-
-!!5. Basic Concepts About Termcap and Terminfo
-
-
-The file /etc/termcap is a text file that lists the
-terminal capabilities. Several applications use the
-termcap information to move the cursor around the screen and do
-other screen-oriented tasks. tcsh, bash, vi and all
-the curses-based applications use the termcap database.
-
-
-The database describes several terminal types. The
-TERM environment variable selects the right behaviour
-at run-time, by naming a termcap entry to be used by
-applications.
-
-
-Within the database, each capability of the terminal appears as a
-two-letter code and a representation of the actual escape sequence
-used to get the desired effect. The separator character between
-different capabilities is the colon (":"). As an example, the audible
-bell, with code "bl", usually appears as "bl=^G". This sequence
-tells that the bell sound is obtained by printing the control-G
-character, the ASCII BEL.
-
-
-In addition to the bl capability, the vb capability is
-recognized. It is used to represent the "visible bell". vb is
-usually missing in the linux entry of the termcap
-file.
-
-
-Most modern applications and libraries use the terminfo database
-instead of termcap. This database uses one file per terminal-type
-and lives in /usr/lib/terminfo; to avoid using huge
-directories, the description of each terminal type is stored in a
-directory named after its first letter; the linux entry,
-therefore, is /usr/lib/terminfo/l/linux. To build a
-terminfo entry you'll ``compile'' the termcap description;
-refer to the tic program and its manual page.
-
-
-
-----
-
-!!6. Defining a Visible Bell
-
-
-You can add the entry for the vb capability in your own termcap
-file, if it doesn't already define one. Dennis Henriksen
-(duke@diku.dk) suggested to insert the following line in the
-termcap entry for linux (note that the entry is called
-console in old distributions):
-
-
-:vb=\E7\E[[?5h\E[[?5l\E[[?5h\E[[?5l\E[[?5h\E[[?5l\E[[?5h\E[[?5l\E8:\
-
-
-The trailing backslash is used to escape the newline in the database.
-Dennis' code does the following (his own words):
-
-
-*Save the cursor position (uust a safety precaution).
-*
-
-*Change the background color several times between normal and reverse.
-*
-
-*Restore the cursor position.
-*
-
-
-
-
-----
-
-!!7. Disabling the Audible Bell on the Text Console
-
-
-If you want to force the visible bell on your console you can use the
-"bl" entry in termcap and define it with the same string
-suggested for "vb" above. This approach is handy if you don't
-want to customize each application (which is described below, anyway).
-I use this option on all the machines where I can run Linux and I
-can't detach the speaker.
-
-
-
-----
-
-!!8. Telling Applications to Avoid Beeping
-
-
-This is an incomplete list of applications that can be instrued
-to use the vb entry for the current terminal type (using either
-the termcap information or the terminfo one):
-
-
-
-
-
-*The X server: use the "xset b" command to select
-the bell's behaviour. The command takes three numeric
-arguments: volume, pitch and duration. "xset -b" disables
-the bell altogether. Configuring the X server affects all
-the applications running on the display.
-
-*
-
-*xterm: xterm can convert each bell to either a visible or
-audible signal. If you use the audible bell, the settings of
-"xset" will apply. The bell in xterm defualts to be
-audible, but you can use the "-vb" command line option
-and the "xterm*visualBell: true" resource to turn it to a
-visible flash. You can toggle visible/audible signaling at
-run-time by using the menu invoked by
-control--left-mouse-button. If you run X you most likely
-won't need the following information.
-
-*
-
-*tcsh (6.04 and later): "set visiblebell". The
-instruction can be placed in .cshrc or can be issued
-interactively. To reset the audible bell just "unset
-visiblebell". To disable any notification issue use "set
-nobeep" instead.
-
-*
-
-*bash (any bash, as fas as I know): put "set bell-style
-visible" in your ~/.bashrc. Possible bell-style's
-are also "none" or "audible".
-
-*
-
-*bash (with readline, as well as other readline
-based applications): put "set prefer-visible-bell" in
-~/.inputrc.
-
-*
-
-*nvi and elvis: put "set flash" in
-~/.exrc or tell ":set flash" interactively (note
-the colon). To disable the visible bell use noflash in
-place of flash.
-
-*
-
-*emacs: put "(setq visible-bell t)" in your
-~/.emacs. It is disabled by "(setq visible-bell
-nil)".
-
-*
-
-*less: use "-q" on command line to use the visual bell,
-use "-Q" to disable any reporting. Default options can be
-put in your environment variable "LESS".
-
-*
-
-*screen: issue the CtrlA-CtrlG command. It changes the
-behaviour of all the virtual screens. Refer to the man page
-under "CUSTOMIZATION" for setting the default.
-
-*
-
-
-
-
-----
-
-!!9. The Dark Side of the Problem
-
-
-The bad news is that not every application uses termcap or
-terminfo. Most small programs feature 'backslash-a' (alarm)
-characters in the C source code. The "alarm" code becomes a literal
-ASCII BEL in the strings as stored in the executable binary. Real
-application don't usually fall in this category, but be careful of C
-newcomers who give you their own programs. Students of computer science
-are the worst of all, granted.
-
-
-The only way to make these programs silent applications is
-spekearectomy, or using the escape sequences by Martin Mares
.
-
-
-
-----
+Describe
[HowToVisualBell
] here
.
