gpm
GPM(8) GPM(8)
NAME
gpm - a cut and paste utility and mouse server for virtual consoles
SYNOPSIS
gpm [ options ]
DESCRIPTION
This package tries to be a useful mouse server for applications run-
ning 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 mecha-
nism; 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 dump-
ing.
The server can be configured to match the user’s taste, and any appli-
cation 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 reasons.
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 kil-
lall gpm can be a better choice.
SPECIAL COMMANDS
Version 1.10 adds the capability to execute special commands on cer-
tain 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 pro-
grammers, because it allows to issue a clean shutdown when the key-
board 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 associ-
ated 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 impossibil-
ity to fork; in these rare case the programmer should be able to shut-
down 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 com-
mands, as gpm runs with superuser permissions. Special commands are
best suited for computers whose mouse can be physically accessed only
by trusted people.
COMMAND LINE OPTIONS
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).
-A[limit]
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 vic-
tim has to do is click the middle mouse button .. As of ver-
sion 1.17.2, this has developed into a more general aging mech-
anism; the gpm daemon can disable (age) selection pasting auto-
matically 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 selec-
tion 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 ;;
esac
-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-but-
ton mice (especially within Emacs). All the button permutations
are allowable.
-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)
-D 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 tap-
ping. number must be 1, 2, or 3, and refers to the button num-
ber 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 nor-
mal ps2 mice
-h 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.
-k 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 charac-
ters 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 -o.
-M 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 tog-
gle 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.
-p 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.
-R[name]
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 cus-
tom 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 proto-
cols are available as repeaters (see -R above), by marking them
with an asterisk (‘‘*’’).
Use -t after you selected the mouse device with -m.
-v Print version information and exit.
-V[verbosity increment]
Raise or decrease the maximum level of messages that will be
logged. Thus a positive argument has the effect of making the
program more verbose. One can also give a negative argument to
hush the program; due to getopt(3) rules, any optional argument
needs to be passed without a space in between! When omitting
the argument, the increment defaults to 1. Default verbosity
level is 5 (LOG_NOTICE).
-2 Force two buttons. This means that the middle button, if any,
will be taken as it was the right one.
-3 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 selec-
tion, 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.
OPERATION
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.)
BUGS
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 hid-
den consoles.
The clients shipped out with gpm are not updated, thus there are
potential security risks when using them.
AUTHORS
Andrew Haylett <ajh@gec-mrc.co.uk> (the original selection code)
Ian Zimmerman <itz@speakeasy.org> (old maintainer)
Alessandro Rubini <rubini@linux.it> (old maintainer (still helps a lot))
Nico Schottelius <nico@schottelius.org> (maintainer)
Many many contributors, to both selection and gpm.
MAINTAINERS
The current maintainer is Nico Schottelius. But without the help of
Alessandro Rubini and the mailing list it would be impossible for him
to maintain gpm. The development mailing list can be reached under
gpm@lists.linux.it. More information on the list is in the README file
part of the source distribution of gpm.
FILES
/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.
SEE ALSO
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.
4th Berkeley Distribution February 2002 GPM(8)
