gpm - a cut and paste utility and mouse server for virtual consoles
This package tries to be a useful mouse server for applications running on the
Linux console. It is based on the "selection" package, and some of
its code comes from selection itself. This package is intended as a
replacement for "selection" as a cut-and-paste mechanism; it also
provides additional facilities. The "selection" package offered the
first cut-and-paste implementation for Linux using two mouse buttons, and the
cut buffer is still called "selection buffer" or just
"selection" throughout this document. The information below is
extracted from the texinfo file, which is the preferred source of information.
The gpm executable is meant to act like a daemon (thus, gpmd would be a better
name for it). This section is meant to describe the command-line options for
gpm, while its internals are outlined in the next section.
Due to restrictions in the ioctl(TIOCLINUX) system call, gpm must be run by the
superuser. The restrictions have been added in the last 1.1 kernels to fix a
security hole related to selection and screen dumping.
The server can be configured to match the user's taste, and any application
using the mouse will inherit the server's attitude. From release 1.02 up to
1.19.2 is was possible for any user logged on the system console to change the
mouse feeling using the -q option. This is no longer possible for security
As of 0.97 the server program puts itself in the background. To kill gpm you can
just reinvoke it with the -k cmdline switch, although killall gpm can be a
Version 1.10 adds the capability to execute special commands on certain
circumstances. Special commands default to rebooting and halting the system,
but the user can specify his/her personal choice. The capability to invoke
commands using the mouse is a handy one for programmers, because it allows to
issue a clean shutdown when the keyboard is locked and no network is available
to restore the system to a sane state.
Special commands are toggled by triple-clicking the left and right button -- an
unlikely event during normal mouse usage. The easiest way to triple-click is
pressing one of the buttons and triple-click the other one. When special
processing is toggled, a message appears on the console (and the speaker beeps
twice, if you have a speaker); if the user releases all the buttons and
presses one of them again within three seconds, then the special command
corresponding to the button is executed.
The default special commands are:
- left button
- Reboot the system by signalling the init process
- middle button (if any)
- Execute /sbin/shutdown -h now
- right button
- Execute /sbin/shutdown -r now
The -S command line switch enables special command processing and allows to
change the three special commands. To accept the default commands use -S
"" (i.e., specify an empty argument). To specify your own commands,
use a colon-separated list to specify commands associated to the left, middle
and right button. If any of the commands is empty, it is interpreted as `send
a signal to the init process'. This particular operation is supported, in
addition to executing external commands, because sometimes bad bugs put the
system to the impossibility to fork; in these rare case the programmer should
be able to shutdown the system anyways, and killing init from a running
process is the only way to do it.
As an example, -S ":telinit 1:/sbin/halt", associates killing init to
the left button, going single user to the middle one, and halting the system
to the right button.
System administrators should obviously be careful about special commands, as gpm
runs with superuser permissions. Special commands are best suited for
computers whose mouse can be physically accessed only by trusted people.
Available command line options are the following:
- -a accel
- Set the acceleration value used when a single motion event
is longer than delta (see -d).
- Start up with selection pasting disabled. This is intended
as a security measure; a plausible attack on a system seems to be to stuff
a nasty shell command into the selection buffer (rm -rf /) including the
terminating line break, then all the victim has to do is click the middle
mouse button .. As of version 1.17.2, this has developed into a more
general aging mechanism; the gpm daemon can disable (age) selection
pasting automatically after a period of inactivity. To enable this mode
just give the optional limit parameter (no space in between !)
which is interpreted as the time in seconds for which a selection is
considered valid and pastable. As of version 1.15.7, a trivial program
called disable-paste is provided. The following makes a good addition to
/etc/profile if you allow multiple users to work on your console.
case $( /usr/bin/tty ) in
/dev/tty[0-9]*) /usr/bin/disable-paste ;;
- -b baud
- Set the baud rate.
- -B sequence
- Set the button sequence. 123 is the normal sequence, 321
can be used by left-handed people, and 132 can be useful with two-button
mice (especially within Emacs). All the button permutations are
- -d delta
- Set the delta value. When a single motion event is longer
than delta, accel is used as a multiplying factor. (Must be
2 or above)
- Do not automatically enter background operation when
started, and log messages to the standard error stream, not the syslog
mechanism. This is useful for debugging; in previous releases it was done
with a compile-time option.
- -g number
- With glidepoint devices, emulate the specified button with
tapping. number must be 1, 2, or 3, and refers to the
button number before the -B button remapping is performed. This
option applies to the mman and ps2 decoding. No button is emulated
by default because the ps2 tapping is incompatible with some normal
- Print a summary of command line options.
- -i interval
- Set interval to be used as an upper time limit for
multiple clicks. If the interval between button-up and button-down events
is less than limit, the press is considered a double or triple
click. Time is in milliseconds.
- Kill a running gpm. This can be used by busmouse users to
kill gpm before running X (unless they use -R or the single-open
limitation is removed from the kernel).
- -l charset
- Choose the inword() look up table. The charset
argument is a list of characters. - is used to specify a range
and \ is used to escape the next character or to provide octal
codes. Only visible character can appear in charset
because control characters can't appear in text-mode video memory,
whence selection is cut.
- -m filename
- Choose the mouse file to open. Must be before -t and
- Enable multiple mode. The daemon will read two different
mouse devices. Any subsequent option will refer to the second device,
while any preceding option will be used for the first device. This option
automatically forces the repeater (-R) option on.
- -o list-of-extra-options
- The option works similary to the ``-o'' option of mount; it
is used to specify a list of ``extra options'' that are specific to each
mouse type. The list is comma-separated. The options dtr, rts or both are
used by the serial initialization to toggle the modem lines like,
compatibly with earlier gpm versions; note however that using -o dtr
associated with non-plain-serial mouse types may now generate an error.
And by the way, use -o after -m and after -t.
- Forces the pointer to be visible while selecting. This is
the behaviour of selection-1.7, but it is sometimes confusing. The default
is not to show the pointer, which can be confusing as well.
- -r number
- Set the responsiveness. A higher responsiveness is used for
a faster cursor motion.
- Causes gpm to act as a repeater: any mouse data received
while in graphic mode will be produced on the fifo /dev/gpmdata in
protocol name, given as an optional argument (no space in between
!). In principle, you can use the same names as for the -t option,
although repeating into some protocols may not be implemented for a while.
In addition, you can specify raw as the name, to
repeat the mouse data byte by byte, without any protocol
translation. If name is omitted, it defaults to
msc . Using gpm in repeater mode, you can configure the
X server to use its fifo as a mouse device. This option is useful
for bus-mouse owners to override the single-open limitation. It is
also an easy way to manage those stupid dual-mode mice which force
you to keep the middle button down while changing video mode. The
option is forced on by the -M option.
- -s number
- Set the sample rate for the mouse device.
- -S commands
- Enable special-command processing, and optionally specify
custom commands as a colon-separated list. See above for a detailed
description of special commands.
- -t name
- Set the mouse type. Use -t help to get a list of allowable
types. Since version 1.18.1, the list also shows which protocols are
available as repeaters (see -R above), by marking them with an asterisk
Use -t after you selected the mouse device with -m.
- Print version information and exit.
- Force two buttons. This means that the middle button, if
any, will be taken as it was the right one.
- Force three buttons. By default the mouse is considered to
be a 2-buttons one, until the middle button is pressed. If three buttons
are there, the right one is used to extend the selection, and the middle
one is used to paste it. Beware: if you use the -3 option with a 2-buttons
mouse, you won't be able to paste the selection.
To select text press the left mouse button and drag the mouse. To paste text in
the same or another console, press the middle button. The right button is used
to extend the selection, like in `xterm'.
Two-button mice use the right button to paste text.
Double and triple clicks select whole word and whole lines. Use of the `-p'
option is recommended for best visual feedback.
If a trailing space after the contents of a line is highlighted, and if there is
no other text on the remainder of the line, the rest of the line will be
selected automatically. If a number of lines are selected, highlighted
trailing spaces on each line will be removed from the selection buffer.
Any output on the virtual console holding the selection will clear the
highlighted selection from the screen, to maintain integrity of the display,
although the contents of the paste buffer will be unaffected.
The selection mechanism is disabled if the controlling virtual console is placed
in graphics mode, for example when running X11, and is re-enabled when text
mode is resumed. (But see BUGS section below.)
The gpm server may have problems interacting with X: if your mouse is a
single-open device (i.e. a bus mouse), you should kill gpm before starting X,
or use the -R option (see above). To kill gpm just invoke gpm -k. This problem
doesn't apply to serial mice.
Two instances of gpm can't run on the same system. If you have two mice use the
-M option (see above).
While the current console is in graphic mode, gpm sleeps until text mode is back
(unless -R is used). Thus, it won't reply to clients. Anyways, it is unlikely
that mouse-eager clients will spur out in hidden consoles.
The clients shipped out with gpm are not updated, thus there are potential
security risks when using them.
Andrew Haylett <email@example.com> (the original selection code)
Ian Zimmerman <firstname.lastname@example.org> (old maintainer)
Alessandro Rubini <email@example.com> (old maintainer (still helps a lot))
Nico Schottelius <firstname.lastname@example.org> (maintainer)
Many many contributors, to both selection and gpm.
The current maintainer is Nico Schottelius. But without the help of Alessandro
Rubini and the mailing list it would be impossible for me to maintain gpm. The
development mailing list can be reached under email@example.com. More
information on the list is in the README file part of the source distribution
/var/run/gpm.pid The PID of the running gpm
/dev/gpmctl A control socket for clients
/dev/gpmdata The fifo written to by a repeater (`-R') daemon.
mev(1) A sample client for the gpm daemon.
gpm-root(1) An handler for Control-Mouse events.
The info file about `gpm', which gives more complete information and explains
how to write a gpm client.