Ubuntu Manpage: mesg - permit or deny messages

NAME

       mesg - permit or deny messages

SYNOPSIS

       mesg  [-s] [-v] [y|n|ye|ne|Y|N|NE] [d] [-p[w|t|k|a]] [-x[w|t|k|n]] [-m[l|c|a]] [-h[Y|y|n]]
       [-r[y|n]] [-b[y|n]]

DESCRIPTION

This is the "Orville write" verison of the standard Unix mesg command.

Mesg with argument n forbids messages via write(1), ojot(1), tel(1), and talk(1) by
revoking non-user write permission on the user's terminal. Mesg with argument y
reinstates permission. All by itself, mesg reports the current state without changing it.

The ne and ye settings mean ``no with exceptions'' and ``yes with exceptions''
respectively. If ne is set, and there is file named .yeswrite in your home directory,
then the users whose logins are listed there may still write you. If ye is set, and there
is a file named .nowrite in your home directory, then the users whose logins are listed
there may not write you. These files have no effect if the permissions are set to n or y.
The .nowrite and .yeswrite files do not need to be permitted to anyone else, and almost
any plausible format will be understood (listing one login name per line is a good
default). Lines may be commented out with a # sign in the first column.

The upper case Y and N do all that the lower case ones do, but may have some additional
affects depending on the installation.

The N argument, if enabled, will attempt to disconnect any write sessions currently
directed at your tty. This is meant to allow users to slam the door on unwelcome writers.
Note that a simple ``mesg n'' will not stop anyone who is already writing you from
continuing to do so, it only prevents new connections from being made. The NE setting
also causes a disconnect, but turns your settings to ne instead of n. The d argument
causes a disconnect, just like ``mesg N'', but does not change your message permissions.

Normally mesg always depermits your tty device, so you can only be written through write
and similar programs. This prevents arbitrary stuff from being redirected to your tty.
When you do ``mesg Y'' your tty is write permitted to others. This is rarely necessary or
desirable.

Mesg can also be used to set other switches that affect Orville write(1). The -p flag
lets you set preferences to (w) write, (t) telegrams, (k) talk, or (a) any. The default
is ``any.'' If you set a preference to write, then people will not be able to send
telegrams or talk requests to you. If they try to send telegrams, they will be asked if
they want to write you instead. Similarly if you prefer telegrams, people will not be
able to write or talk to you, and if you prefer talk, people will not be able to write or
tel you. You can designate two preferences, like ``mesg -pt -pw'' to allow people to
write or telegram you, but not make talk requests to you. Alternately, you can use the -x
flag to block particular programs. Doing ``mesg -xk'' blocks only the talk program, and
is equivalent to ``mesg -pt -pw''. Similarly the ``-xn'' flag excludes no programs and is
equivalent to ``-pa''. Trying to block all programs just turns you permissions off.

The -m flag lets you set modes to (l) line, (c) character, or (a) any. The default is
``any.'' If you set a mode, then all writes to you will be done in that mode. If you
leave it as ``any,'' the choice is left to the writer. This will not affect connections
already in progress, only future ones.

The -r flag lets you turn on or off the recording to telegrams sent to you. If it is
enabled, everytime you are sent a telegram (or a write with input taken from a file), the
text of the messages is saved in a file named .lastmesg in your home directory. This
allows you to redisplay the last message sent to you using the huh(1) command. If a
screen clear ate a telegram message before you had time to read it, then the huh command
lets you see it again. Note that only the last message sent is stored. The file is
permitted to be readable to you only.

The -b flag lets you tell the write and talk programs whether or not to beep when a person
writes you or sends you a telegram. The default is to beep.

The -h flag lets you turn on or off your helper status. People who designate themselves
as helpers are announcing their willingness to help out lost users. Their accounts will
be marked on the output of the finger(1) command, and if anyone does a write or ojot(1) to
``help'' they automatically get connected to someone who has a help flag set. Normally,
turning your permissions off also turns your helper-status off, but if you set the -h flag
to Y, then you will remain a helper even when your message permissions are off. This
means you can receive help requests, but not normal messages.

On some systems there is a restricted list of users who may be helpers. This is usually
kept in the file /etc/helpers, one login name per line. If such a file exists then you
will have to get the operators to add your name to it to be able to designate yourself as
a helper.

If no new settings are given to mesg, then it just reports on the current settings.
Normally it prints the message permissions, but if a -h, -p, -r, or -m flag was given
without a new value after it, then the current status of that switch will be printed
instead. If you use the -s flag, then this output will be suppressed. The command still
reports the status of the selected switch with its numeric return code.

If you use the -v flag, all switch settings will be reported in a verbose mode.

The numeric values returned as return codes (see below) can also be used to set switches.
Thus ``mesg 0 -m2'' sets permissions on, and the mode to any. This makes it easy for
shell scripts to restore settings that were stored previously.

The argument syntax is actually a lot looser than mentioned above. The dashes before
options may be omitted, Spaces may be added or omitted anywhere in the argument list.

FILES

       /dev/tty*
       /etc/wrttmp
       /etc/helpers

DIAGNOSTICS

       Exit status is -1 on an error.  Otherwise a code is returned reporting the status  of  one
       of  the settings.  If the arguments included -h, -p, or -m flags without a new value after
       it, then the last of these listed will be reported.  Otherwise, if any options  were  set,
       the  last  of those listed in the argument list will be reported.  And if nothing was set,
       then message permissions are reported.

       When message permissions, record settings, or helper settings are  reported,  0  indicates
       'y',  and  1  indicates  'n'.  When preferences are reported, 1 indicates 'w', 2 indicates
       't', and 4 indicates 'k', and any combinations are returned as sums of these values.  When
       modes are reported, 0 indicates 'l', 1 indicates 'c', and 2 indicates 'a'.

BUGS