This may seem a bit of a strange question, but it occurred to me that when typing a command such as the following, I always have to copy and paste the character from Wikipedia.
echo '5 μs' >> /tmp/Output
Is there a way to input such a character directly using an escape sequence on keyboard shortcut on a standard English keyboard?
For example, in Vim, one can do C-k,m* to produce this character.
Yes, there are at least this four (five?) ways:
AltGr
Make your keyboard layout English (international AltGr dead keys).
Then the right Alt key is the AltGr key. Pressing AltGr-m will generate a µ. Many other keys also generate other characters: AltGr-s for ß, and Shift-AltGr-s for §.
There is a separate keyboard layout for the console (the true consoles at AltCtrlF1 up to F6) and one for the GUI in X. Changing either depends on your distro (CentOS, Fedora, Debian, etc.) and Display manager (gnome, kde, xfce, etc.). For example, installing xfce4-xkb-plugin will allow a button on a panel to configure the keyboard and switch between several keyboard layouts for X in XFCE.
Compose
Make some key the Compose key. Then, presing Compose, releasing it, pressing /, releasing it, and then u will generate a µ.
Defining a Compose key is usually done with xkb or with a keyboard layout applet.
For example, in Gnome usually available at Region & Language section, or maybe, Switch Keyboard Layout Easily.
Unicode
There is a generic way to type any Unicode character (if your console supports it). Yes any codepoint of the 1,111,998 possible characters (visible if your font(s) could draw them). Press, as one chord (at the same time) ShiftCtrlu, release them (Probably, an underlined u̲ will appear), then type b5 which is the Unicode codepoint (always in Hex) for the character. And to end, type space or enter (at least).
Readline
In a bash prompt (as you tagged the question) is possible to use readline to generate a µ (mu).
bind '"\eu": "µ"'
Or add the line:
"\eu": "µ"
to ~/.inputrc, read it with Alt-x Alt-r or start a new bash shell (execute bash) and when you type:
Alt-u
An µ will appear.
Input method
Probably too much for a short answer like this.
A mistake:
Technically, the character requested in the question was Unicode \U3bc while this answer has provided solutions for \Ub5. Yes, they are different, my mistake, sorry.
$ unicode $(printf '\U3bc\Ub5')
U+03BC GREEK SMALL LETTER MU
UTF-8: ce bc UTF-16BE: 03bc Decimal: μ Octal: \01674
μ (Μ)
Uppercase: 039C
Category: Ll (Letter, Lowercase)
Unicode block: 0370..03FF; Greek and Coptic
Bidi: L (Left-to-Right)
U+00B5 MICRO SIGN
UTF-8: c2 b5 UTF-16BE: 00b5 Decimal: µ Octal: \0265
µ (Μ)
Uppercase: 039C
Category: Ll (Letter, Lowercase)
Unicode block: 0080..00FF; Latin-1 Supplement
Bidi: L (Left-to-Right)
Decomposition: <compat> 03BC
And technically, the only valid solutions are number 3 and 4. In 3 the Unicode number could be changed from b5 to 3bc to get even this Greek character. In 4 just copy the correct character and done.
b5 and 3bc have as Uppercase 39c. So, both are the lowercase of MU.
AltGr
Its quite possible and already done by changing the AltGr-g (with xkb) to:
key <AC05> { [ g, G, dead_greek, dead_greek ]};
And then typing AltGr-g m to get a true greek-mu.
Compose
The Compose table is incorrect, even the Greek Compose file (/usr/share/X11/locale/el_GR.UTF-8/Compose) lists:
<Multi_key> <slash> <u> : "µ" mu
<Multi_key> <u> <slash> : "µ" mu
<Multi_key> <slash> <U> : "µ" mu
<Multi_key> <U> <slash> : "µ" mu
Those compositions as Greek, which they are not.
The correct solution for compose is to include an ~/.XCompose for greek and reboot.
Unicode
Works as posted, with unicode number 3bc
Readline
Works as posted, change the effective character to any wanted.
µ (micro, U+00B5), not what was asked in the question, μ (mu, U+03BC).
– Sparhawk
Dec 11 '18 at 11:50
μ in μs in the question is indeed U+00B5.
– JdeBP
Dec 11 '18 at 13:55
compose - m - u also works and is perhaps easier to memorize than compose - / - u. Both do the micro version.
– spectras
Dec 11 '18 at 13:57
compose-mu is easier to remember, but I like compose-g-m for Greek-Mu better (just personal preference, not that it means much).
–
Dec 11 '18 at 14:07
If you enable your compose key, you can print this symbol with the compose/u sequence, like so: µ
The full range of symbols available, and their respective key sequences, is documented on the Ubuntu wiki.
µ (micro, U+00B5), not what was asked in the question, μ (mu, U+03BC).
– Sparhawk
Dec 11 '18 at 11:51
Compose * m if you use something like https://github.com/kragen/xcompose/blob/master/dotXCompose
– Mikel
Dec 11 '18 at 15:41
CIN-file input methods are usable in X11 and in my user-space virtual terminals. One of the commonly-collected ones, greek.cin, has the mu character. One simply enters m (lower case) and it is the only conversion.
One can modify greek.cin to add micro, providing a second conversion, although visually it will be quite confusing, making it hard to select the correct one during conversion selection, if they both map from m. A better conversion would map micro to U+00B5:
micro μ
Your X11 keyboard map or your virtual terminal might not implement this, but if it does there is a standard country-independent key sequence (of two key chords) for the mu character defined by ISO/IEC 9995: ⇨ Group 2 Select B07
Where implemented, this so-called common secondary group of ISO/IEC 9995 is not supposed to vary by the selected country's layout, and is always available.
However, there is no common secondary group sequence for the micro prefix character.
The specifics of keyboard layouts are beyond the scope of this answer, and there are plenty of answers here dealing with them.
There is a keyboard layout for X11 applications, there is a possibly related keyboard layout for kernel virtual terminals (if your operating system has such), and there is are keyboard layouts for user-space virtual terminals (if you are using such). Layouts generally provide such characters as a chord with ⇧ Level 2 Shift or ⇮ Level 3 Shift in conjunction with a main keypad key.
Some X11 keyboard maps furthermore define (as an optional addendum) a compose key which begins key sequences (of multiple key chords) that map to such characters. In the conventional X11 composition set, as documented by David Monniaux years ago, the mu character is the sequence Compose M U or the sequence Compose / U. Note that it is conflated with the micro prefix character.
Consult your VT and X11 keyboard maps for information about what chord is mapped, if any. Check your configuration for whether you have enabled the compose key option in X11.
The ch, de, it, nl, and no virtual terminal keyboard maps in FreeBSD provide the mu character as the chord ⇮ Level 3 Shift+B07 (M):
% sed -n -e '2,5p;/0xb5/p' /usr/share/vt/keymaps/de.kbd /usr/share/vt/keymaps [pts/4.10009.1] # alt # scan cntrl alt alt cntrl lock # code base shift cntrl shift alt shift cntrl shift state # ------------------------------------------------------------------ 050 'm' 'M' cr cr 0xb5 0xb5 cr cr C %
But other maps either do not have it or define a different chord. In the fr keyboard map it is ⇧ Level 2 Shift+C12 (EUROPE1):
% sed -n -e '2,5p;/0xb5/p' /usr/share/vt/keymaps/fr.kbd /usr/share/vt/keymaps [pts/4.10011.1] # alt # scan cntrl alt alt cntrl lock # code base shift cntrl shift alt shift cntrl shift state # ------------------------------------------------------------------ 043 '*' 0xb5 nop nop '#' '~' nop nop O %
And it is not mapped in the uk keyboard map at all. Nor do any of them have the micro prefix character.
Other methods are specific to application input handling libraries or to particular terminal emulators, whereas input methods and X11/VT keyboard maps are not application-specific.
Some terminal emulators provide other ways of entering characters, by their Unicode code points. Readline can of course be configured to map input sequences to this character, as also can ZLE. And you have already mentioned VIM in the question.
μs. – JdeBP Dec 11 '18 at 13:46M-x set-input-method RET greekandC-x RET C-\ greekwill set emacs to a greek keyboard where the usual place formis the greek letterμ(and alpha isabeta isb, etc.). – Dec 11 '18 at 13:50