mapchan [-o] [-d] [channel]
mapchan configures the mapping of information input and output of the UNIX system. The mapchan utility is intended for users of applications that employ languages other than English (character sets other than 7 bit ASCII).
mapchan translates codes sent by peripheral devices, such as terminals, to the internal character set used by the UNIX system. mapchan can also map codes in the internal character set to other codes for output to peripheral devices (such as terminals, printers, console screen, etc.). Note that PC keyboard configuration is accomplished through the mapkey(1M) utility.
mapchan has several uses: to map a channel (-a or -s); to unmap a channel (-n and optionally -a); or to display the map on a channel (optionally -o,-d, channels).
mapchan with no options displays the map on the user's channel. The map displayed is suitable as input for mapchan.
The options are :
The user must own the channel in order to map it. The privileged user can map any channel. Read or write permission is required to display the map on a channel.
Each tty device channel (display adapter and video monitor on computer, parallel port, serial port, etc.) can have a different map. When the UNIX system boots, mapping is off for all channels.
mapchan is usually invoked in the /etc/rc2 file. This file is executed when the system enters the multiuser mode and sets up the default mapping for the system. Users can invoke mapchan when they log in by including a mapchan command line in their .profile or .login file. In addition, users can remap their channel at any time by invoking mapchan from the command line. channels not listed in the default file are not automatically mapped. channels are not changed on logout. Whatever mapping was in place for the last user remains in effect for the next user, unless they modify their .profile or .login file.
For example, the default file /etc/default/mapchan can obtain:
tty1 tty2 ibm tty3 wy60.ger lp ibm
The default directory containing mapfiles is /usr/lib/mapchan. The default directory containing channel files is /dev. Full pathnames may be used for channels or mapfiles. If a channel has no entry, or the entry field is blank, no mapping is enabled on that channel. Additional channels added to the system (for example, adding a serial or parallel port), are not automatically entered in the mapchan default file. If mapping is required, the system administrator must make the entries. The format of the mapfiles is documented in the mapchan(4) manual page.
One to one mapped characters are displayed when the key is pressed and the mapped value is passed to the kernel.
Certain keys are designated as dead keys in the mapfile. Dead key sequences are two keystrokes that produce a single mapped value that is passed to the kernel. The dead key is usually a diacritical character, the second key is usually the letter being modified. For example, the sequence ``'e'' could be mapped to the ASCII value 0xE9, and displayed as ``e'''.
One key is designated as the compose key in the mapfile.
Compose key sequences are composed of three keystrokes that produce a single
mapped value that is passed to the kernel.
The compose key is usually a seldom used character or CTRL-letter
combination.
The second key is usually the letter being modified.
The third key may be another character being combined, or a
diacritical character.
For example, if ``@'' is the
compose key, the sequence @ c O could be mapped to the ASCII value
0xA9, and displayed as ©.
Characters are not echoed to the screen during a dead or compose sequence. The mapped character is echoed and passed to the kernel once the sequence is correctly completed.
Characters are always put through the input map, even when part of dead or compose sequences. The character is then checked for the internal value. The value may also be mapped on output. This should be kept mind when preparing map files.
The following conditions will cause an error during input:
If the mapfile contains the keyword beep, a bell sounds when either of the above conditions occurs. In either case, the characters are not echoed to the screen, or passed to the kernel.
In order to allow for character sequences sent to control the terminal (move the cursor, and so on) rather than to print characters on the screen, mapchan allows characters sequences to be specified as special sequences which are not passed through the normal mapping procedure. Two sections may be specified, one for each of the input (keyboard) and output (screen) controls.
Several partial map files are provided as examples. They must be modified for use with specific peripheral devices. Consult your hardware manual for the codes needed to display the desired characters. Two map files are provided for use with the console device: /usr/lib/mapchan/ibm for systems with a standard PC character set ROM, and /usr/lib/mapchan/iso for systems with an optional ISO 8859/1 character set ROM.
Care should be taken that the stty settings (see stty(1)) are correct for 8-bit terminals. The /etc/gettydefs file may require modifications to allow logging with the correct settings.
7-bit U.S ASCII (ANSI X3.4) should be used if no mapping is enabled on the channel.
Printers can be mapped, output only, and can either be sent 8-bit codes or one-to-many character strings using mapchan. Line printer spooler interface scripts can be used (setuid root) to change the output map on the printer when different maps are required (as in changing print wheels to display a different character set). See lpadmin(1M) and lp(7) for information on installing and administering interface scripts.
Not all terminals or printers can display all the characters that can be represented using this utility. Refer to the device's hardware manual for information on the capabilities of the peripheral device.
Use of mapfiles that specify a different internal character set per channel, or a set other than the 8-bit ISO 8859 set supplied by default can cause strange side effects. It is especially important to retain the 7-bit ASCII portion of the character set (see ascii(5)). System utilities and many applications assume these values.
Media transported between machines with different internal code set mappings may not be portable as no mapping is performed on block devices, such as tape and floppy drives. However, trchan with an appropriate mapfile can be used to translate from one internal character set to another.
Do not set ISTRIP (see stty(1)) when using mapchan. This option causes the eighth bit to be stripped before mapping occurs.