Outputs to STDERR

Outputting to STDERR is now at +33/-21 as an allowed default, which is positive but contested. This is a CW answer to collect answers that just invoke an error in a language where error messages includes the language name.

Haskell, 1 byte

1

Error:

Parse error: naked expression at top level
Perhaps you intended to use TemplateHaskell

Lua, 1 byte

1

Error:

lua: .code.tio:1: syntax error near <eof>

(file name is unimportant)

Batch, 1 byte

~

Error:

'~' is not recognized as an internal or external command,
operable program or batch file.

tinylisp, 5 bytes

(c()1

Error:

Error: cannot cons to non-list in tinylisp

C (gcc), 1 byte

9

Error:

/dev/stdin:1:1: error: expected identifier or ‘(’ before numeric constant

R, 1 byte

)

Error:

Error: unexpected ')' in ")"

Java bytecode, 0 bytes

Error:

Exception in thread "main" java.lang.ClassFormatError: Truncated class file

Groovy, 1 byte

a

Note that a can be replaced with any other character

Error:

groovy.lang.MissingPropertyException: No such property: a ...

MATLAB, 1 byte

\

Error:

Error: Unexpected MATLAB operator.

PHP, 3 bytes

<?=

Error:

PHP Parse error:  syntax error, unexpected end of file in /home/runner/.code.tio on line 1

CJam, 1 byte

/

Error:

/
^
RuntimeException: The stack is empty
Java exception:
java.lang.RuntimeException: The stack is empty
    at net.aditsu.cjam.CJam.pop(CJam.java:75)
    at net.aditsu.cjam.Op2.run(Op2.java:10)
    at net.aditsu.cjam.Block.run(Block.java:304)
    at net.aditsu.cjam.CJam.runCode(CJam.java:210)
    at net.aditsu.cjam.CJam.main(CJam.java:240)

Twig, 2 bytes

Twig is a template language written in PHP. It's possible that this is a polyglot.

{{
{%
{#

Error:

PHP Fatal error:  Uncaught exception 'Twig_Error_Syntax' with message [...] in [...][...]:n:
Stack trace:
#0 [...]

The message varies depending on which program you choose.

S.I.L.O.S, 2 bytes

x+

Try it online! Trivially invokes undocumented behavior. Silos is the name of the language.

Python, 6 bytes

pYTHON

As the character restriction is case insensitive, and the output doesn't have to be in the correct case, this is a valid answer. The error message it produces is something like this:

Traceback (most recent call last):
  File ".code.tio", line 1, in <module>
    pYTHON
NameError: name 'pYTHON' is not defined

Try it online! (outputs to 'debug' tab)

JavaScript, 10 bytes

jAVAsCRIPT

This produces the following error message or similar in all environments:

ReferenceError: jAVAsCRIPT is not defined

MATL, 1 byte

Y

Output is through STDERR, which is allowed by default.

The output from the offline compiler is

Error using matl_parse (line 339)
MATL error while parsing: Y not recognized at position 1
Error in matl (line 234)
    S = matl_parse(s, useTags); 

Or try it online! (expand "debug" section).

SmileBASIC, 11 bytes

sPsET.,1474

Eqivilant to SPSET 0,1474. Sets sprite 0 to definition 1474, which is the SmileBASIC logo.

HTML, 24 20 bytes

HTML

HTML, 16 bytes

As pointed out by @Bob, modern browsers will recognize HTML entities without semicolons, though it's technically invalid HTML. Of course, it's perfectly valid for code golf.

&#72&#84&#77&#76

HTML, 4 bytes

And of course, the uninteresting answer.

html

Also, see my CSS answer.

R, 1 byte:

T

T is an alias for the constant TRUE. So the output for the above is:

[1] TRUE

Since junk is allowed around the name, the “R” in there is the language name.

(As noted in a comment elsewhere, pretty much any single letter and many glyphs will work equally well because they trigger the message “Error: …”, which contains “r”.)

Python 2/3, 28 17 (3) and 15 (2) bytes

Python 3

exec("\150elp()")

It concatenates the strings uses the octal 150 which is h and "elp()" and runs the result. This prints the help() command which says "Welcome to Python 3.5's help utility!", meeting the requirements.

Python 2

This uses exactly the same method as the above but without the parentheses

exec"\150elp()"

Try it online

C, 0 bytes.

/usr/lib/gcc/i586-linux-gnu/5/../../../i386-linux-gnu/crt1.o: In function `_start':
(.text+0x18): undefined reference to `main'
collect2: error: ld returned 1 exit status

Try it online!

Vim, 0 bytes

When you start Vim, the editor displays a splash screen which looks like this:

You can see it says Vim here:

Previous answer:

Vim, 1 byte

<Ctrl-C>

In Vim 8, pressing will display Type :quit<Enter> to exit Vim at the last line. I'm not completely sure if this counts.

V, 2 bytes

¬U

Try it online!

The obvious answer is:

év~

Try it online!

Which is "Insert the letter 'v', and toggle case". However, since you allow for junk output before/after the language name, this works too.

The ¬ command takes two characters for input, and inserts every ASCII character between them. If we don't supply the second character, it automatically defaults to ÿ (ASCII 0xff), so this program inserts every character in the latin1 encoding between U and ÿ.

Huh?, 0 bytes

^{(no, there's nothing in that code block)}

The language is named for its output, so...

In the implementation I checked, the interpreter takes the length mod 8 of each line of a given file, and switches depending on the result. For zero, it prints Huh?. Since it strips trailing newlines, you could also do a 1 byte (\n) version.

Note that it's not outputting to stderr or caseswapping or any other trickery. It's just that Huh?'s very confused interpreter finally came in handy.

MATLAB, 3 bytes

ver

Output is as follows. Irrelevant info has been replaced by [...]). Some parts of the output may change depending on version, installed toolboxes etc.

-----------------------------------------------------------------------------------------
MATLAB Version: 8.6.0.267246 (R2015b)
MATLAB License Number: [...]
Operating System: [...]
Java Version: Java 1.7.0_60-b19 with [...]
-----------------------------------------------------------------------------------------
MATLAB                                                Version 8.6         (R2015b)
Communications System Toolbox                         Version 6.1         (R2015b)
Curve Fitting Toolbox                                 Version 3.5.2       (R2015b)
[...]
Wavelet Toolbox                                       Version 4.15        (R2015b)

JAVA, 1 byte

1

The output to stderr is:

Main.java:1: error: class, interface, or enum expected
1
^
1 error
Error: Could not find or load main class Main
Command exited with non-zero status 1
    Command being timed: "/srv/wrappers/java-openjdk"
    User time (seconds): 1.40
    System time (seconds): 0.80
    Percent of CPU this job got: 40%
    Elapsed (wall clock) time (h:mm:ss or m:ss): 0:05.40
    Average shared text size (kbytes): 0
    Average unshared data size (kbytes): 0
    Average stack size (kbytes): 0
    Average total size (kbytes): 0
    Maximum resident set size (kbytes): 44564
    Average resident set size (kbytes): 0
    Major (requiring I/O) page faults: 205
    Minor (reclaiming a frame) page faults: 11301
    Voluntary context switches: 2666
    Involuntary context switches: 1677
    Swaps: 0
    File system inputs: 78312
    File system outputs: 0
    Socket messages sent: 0
    Socket messages received: 0
    Signals delivered: 0
    Page size (bytes): 4096
    Exit status: 1 

brainfuck, 54 bytes

+[[-<]-[->]<-]<.<<<<.>>>>-.<<-.<.>>.<<<+++.>>>---.<++.

Outputs brainfuck, assuming an 8-bit tape open on the left. Try it online!

As always, partial credits go to @primo's Hello, World! answer.

Alternatives with different casing

Brainfuck (62 bytes):

+[<-[-<]-[->]<<]<---.<<<<<<--.>>>-.<+.<.>---.<<+++.>>---.<---.

BrainFuck (68 bytes):

-[[-<]->+[->]<-]<<.<<<<<--.>>+.<-.+++++.>>>------.<<<<+++.>>++.<---.

><>, 12 10 bytes

"2,:o:2-o|

This will continually print ><> until the interpreter runs out of space.

Try it online!

12 byte version below for those who like a clean output. Recommended by Aaron (no error, 1 output)

":3+:o$1+oo;

Python, 27 53 49 48 45 bytes

-3 bytes from @wizzwizz4

exec eval('"IMpORT THIS".LOWER()'.swapcase())

Prints the following text, which has "Python" on the first line.

The Zen of Python, by Tim Peters

Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.
Flat is better than nested.
Sparse is better than dense.
Readability counts.
Special cases aren't special enough to break the rules.
Although practicality beats purity.
Errors should never pass silently.
Unless explicitly silenced.
In the face of ambiguity, refuse the temptation to guess.
There should be one-- and preferably only one --obvious way to do it.
Although that way may not be obvious at first unless you're Dutch.
Now is better than never.
Although never is often better than *right* now.
If the implementation is hard to explain, it's a bad idea.
If the implementation is easy to explain, it may be a good idea.
Namespaces are one honking great idea -- let's do more of those!

Python 2 (1 byte)

è

output...:

bash CLI, 9

printf $0

If you want an actual script and not just a command at the interactive command line, then you can do this:

bash, 13

printf $SHELL

Outputs /bin/bash

dc, 6

25699P

Outputs dc.

Try it online.

CSS, 25 bytes

:after{content:'\43\53\53

Note that extra markup is added to Stack Overflow snippets, causing "CSS" to be displayed more than once. Open an .html file with contents

<style>:after{content:'\43\53\53

to see the result as intended.

Pip, 8 bytes

'IWR C80

Takes the character I and WRaps it in Chr(80), resulting in PIP. Try it online!

Using the I feels a bit like cheating, so here are two 9-byte solutions that don't use any of PpIi:

z@8WRz@15
(z8+^707)

Both output pip. I'm particularly pleased with the second one:

    ^707   Split 707 into a list of characters        [7;0;7]
  8+       Add 8 to each one                          [15;8;15]
(z      )  Use list to index into lowercase alphabet  ["p";"i";"p"]
           By default, lists are printed without a separator

For proper capitalization, we need a 10-byte solution:

'IWR C80Vx

How this one works is left as an exercise for the reader. ;^)

C#, 60 67 bytes

class P{static void Main(){System.\u0043onsole.Write("\x43\x23");}}

brainfuck, 105 Bytes

--[----->+<]>----.[--->+<]>----.+++[->+++<]>++.++++++++.+++++.--------.-[--->+<]>--.+[->+++<]>+.++++++++.

Try it online here

R, 11 bytes

cat("\x52")

Try it online!

Perl 5, 36 bytes (35 + 1 for -E)

$^X=~s/.+(.)(...)$/\U$1\E$2/;say$^X

Run with the -E flag.

$ perl -E 'say$^X=~s/.+(.)(...)$/\U$1\E$2/r'
Perl

The variable $^X is the path to the executable that is running the current program. Since the Perl interpreter is called perl, we then need to make he first letter upper-case. But the ucfirst function contains an r, which is not allowed, so we have to resort to \U and \E, which turn upper-case-conversion on and off.

We cannot use the /r modifier for s/// to return the changed string because the r is not allowed.

It's important to know that the name of the Perl programming language is Perl, and the name of the interpreter is perl with a lower-case p. There is no PERL.

BASIC (ZX Spectrum), 4 bytes

õ°""

Note: In the ZX Spectrum character set, these bytes display as

PRINT VAL ""

which outputs

C Nonsense in BASIC, 0:1

because the empty string is not a valid numeric expression. (I could of course have used any statement that takes a single integer.) If this answer is unacceptable, then for 6 bytes you can write a program consisting of a single line with one of the keywords that accepts no arguments, then use POKE to replace it with an illegal keyword, then attempt to RUN the program.

C 24 20 Bytes (Clang 3.8.1)

Thanks to @squeamish ossifrage for helping me save 4 bytes.

main(){putchar(67);}

Vim, 3 bytes

:h<CR>

Try it online!

This opens up the default help file and outputs:

*help.txt*  For Vim version 7.4.  Last change: 2016 Mar 31

                        VIM - main help file
                                                                         k
      Move around:  Use the cursor keys, or "h" to go left,        h   l
                    "j" to go down, "k" to go up, "l" to go right.   j
Close this window:  Use ":q<Enter>".
   Get out of Vim:  Use ":qa!<Enter>" (careful, all changes are lost!).

Jump to a subject:  Position the cursor on a tag (e.g. |bars|) and hit CTRL-].
   With the mouse:  Double-click the left mouse button on a tag, e.g. |bars|.
        Jump back:  Type CTRL-T or CTRL-O.  Repeat to go further back.

Get specific help:  It is possible to go directly to whatever you want help
                    on, by giving an argument to the |:help| command.
                    Prepend something to specify the context:  *help-context*

                          WHAT          PREPEND    EXAMPLE  ~
                      Normal mode command          :help x
                      Visual mode command     v_       :help v_u
                      Insert mode command     i_       :help i_<Esc>
                      Command-line command    :    :help :quit
                      Command-line editing    c_       :help c_<Del>
                      Vim command argument    -    :help -r
                      Option              '    :help 'textwidth'
                      Regular expression      /    :help /[
                    See |help-summary| for more contexts and an explanation.

  Search for help:  Type ":help word", then hit CTRL-D to see matching
                    help entries for "word".
                    Or use ":helpgrep word". |:helpgrep|

VIM stands for Vi IMproved.  Most of VIM was made by Bram Moolenaar, but only
through the help of many others.  See |credits|.
------------------------------------------------------------------------------
                                                *doc-file-list* *Q_ct*
BASIC:
|quickref|  Overview of the most common commands you will use
|tutor|     30 minutes training course for beginners
|copying|   About copyrights
|iccf|      Helping poor children in Uganda
|sponsor|   Sponsor Vim development, become a registered Vim user
|www|       Vim on the World Wide Web
|bugs|      Where to send bug reports

USER MANUAL: These files explain how to accomplish an editing task.

|usr_toc.txt|   Table Of Contents

Getting Started ~
|usr_01.txt|  About the manuals
|usr_02.txt|  The first steps in Vim
|usr_03.txt|  Moving around
|usr_04.txt|  Making small changes
|usr_05.txt|  Set your settings
|usr_06.txt|  Using syntax highlighting
|usr_07.txt|  Editing more than one file
|usr_08.txt|  Splitting windows
|usr_09.txt|  Using the GUI
|usr_10.txt|  Making big changes
|usr_11.txt|  Recovering from a crash
|usr_12.txt|  Clever tricks

Editing Effectively ~
|usr_20.txt|  Typing command-line commands quickly
|usr_21.txt|  Go away and come back
|usr_22.txt|  Finding the file to edit
|usr_23.txt|  Editing other files
|usr_24.txt|  Inserting quickly
|usr_25.txt|  Editing formatted text
|usr_26.txt|  Repeating
|usr_27.txt|  Search commands and patterns
|usr_28.txt|  Folding
|usr_29.txt|  Moving through programs
|usr_30.txt|  Editing programs
|usr_31.txt|  Exploiting the GUI
|usr_32.txt|  The undo tree

Tuning Vim ~
|usr_40.txt|  Make new commands
|usr_41.txt|  Write a Vim script
|usr_42.txt|  Add new menus
|usr_43.txt|  Using filetypes
|usr_44.txt|  Your own syntax highlighted
|usr_45.txt|  Select your language


REFERENCE MANUAL: These files explain every detail of Vim.  *reference_toc*

General subjects ~
|intro.txt| general introduction to Vim; notation used in help files
|help.txt|  overview and quick reference (this file)
|helphelp.txt|  about using the help files
|index.txt| alphabetical index of all commands
|help-tags| all the tags you can jump to (index of tags)
|howto.txt| how to do the most common editing tasks
|tips.txt|  various tips on using Vim
|message.txt|   (error) messages and explanations
|quotes.txt|    remarks from users of Vim
|develop.txt|   development of Vim
|debug.txt| debugging Vim itself
|uganda.txt|    Vim distribution conditions and what to do with your money

Basic editing ~
|starting.txt|  starting Vim, Vim command arguments, initialisation
|editing.txt|   editing and writing files
|motion.txt|    commands for moving around
|scroll.txt|    scrolling the text in the window
|insert.txt|    Insert and Replace mode
|change.txt|    deleting and replacing text
|indent.txt|    automatic indenting for C and other languages
|undo.txt|  Undo and Redo
|repeat.txt|    repeating commands, Vim scripts and debugging
|visual.txt|    using the Visual mode (selecting a text area)
|various.txt|   various remaining commands
|recover.txt|   recovering from a crash

Advanced editing ~
|cmdline.txt|   Command-line editing
|options.txt|   description of all options
|pattern.txt|   regexp patterns and search commands
|map.txt|   key mapping and abbreviations
|tagsrch.txt|   tags and special searches
|quickfix.txt|  commands for a quick edit-compile-fix cycle
|windows.txt|   commands for using multiple windows and buffers
|tabpage.txt|   commands for using multiple tab pages
|syntax.txt|    syntax highlighting
|spell.txt| spell checking
|diff.txt|  working with two to four versions of the same file
|autocmd.txt|   automatically executing commands on an event
|filetype.txt|  settings done specifically for a type of file
|eval.txt|  expression evaluation, conditional commands
|fold.txt|  hide (fold) ranges of lines

Special issues ~
|print.txt| printing
|remote.txt|    using Vim as a server or client
|term.txt|  using different terminals and mice
|digraph.txt|   list of available digraphs
|mbyte.txt| multi-byte text support
|mlang.txt| non-English language support
|arabic.txt|    Arabic language support and editing
|farsi.txt| Farsi (Persian) editing
|hebrew.txt|    Hebrew language support and editing
|russian.txt|   Russian language support and editing
|ft_ada.txt|    Ada (the programming language) support
|ft_sql.txt|    about the SQL filetype plugin
|rileft.txt|    right-to-left editing mode

GUI ~
|gui.txt|   Graphical User Interface (GUI)
|gui_w32.txt|   Win32 GUI

Interfaces ~
|if_cscop.txt|  using Cscope with Vim
|if_pyth.txt|   Python interface
|if_ruby.txt|   Ruby interface
|debugger.txt|  Interface with a debugger
|sign.txt|  debugging signs

Versions ~
|vim_diff.txt|  Main differences between Nvim and Vim
|vi_diff.txt|   Main differences between Vim and Vi
                                                *sys-file-list*
Remarks about specific systems ~
|os_win32.txt|  MS-Windows
                                                *standard-plugin-list*
Standard plugins ~
|pi_gzip.txt|      Reading and writing compressed files
|pi_netrw.txt|     Reading and writing files over a network
|pi_paren.txt|     Highlight matching parens
|pi_tar.txt|       Tar file explorer
|pi_vimball.txt|   Create a self-installing Vim script
|pi_zip.txt|       Zip archive explorer

LOCAL ADDITIONS:                *local-additions*

------------------------------------------------------------------------------
*bars*      Bars example

Now that you've jumped here with CTRL-] or a double mouse click, you can use
CTRL-T, CTRL-O, g<RightMouse>, or <C-RightMouse> to go back to where you were.

Note that tags are within | characters, but when highlighting is enabled these
characters are hidden.  That makes it easier to read a command.

Anyway, you can use CTRL-] on any word, also when it is not within |, and Vim
will try to find help for it.  Especially for options in single quotes, e.g.
'hlsearch'.

------------------------------------------------------------------------------
 vim:tw=78:fo=tcq2:isk=!-~,^*,^\|,^\":ts=8:ft=help:norl:

Groovy, 1 byte

a

In fact, a can be replaced by any character except the ones in Groovy. This raises a MissingPropertyException and outputs the following to STDERR-

groovy.lang.MissingPropertyException: No such property: a ...

Labyrinth, 31 28 bytes

76.65.66.89.82.73.78.84.72.@

Try it online!

Prints LABYRINTH.

R, 10 bytes

citation()

Outputs :

To cite R in publications use:

R Core Team (2016). R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. URL https://www.R-project.org/.

A BibTeX entry for LaTeX users is

@Manual{,
title = {R: A Language and Environment for Statistical Computing},
author = {{R Core Team}},
organization = {R Foundation for Statistical Computing},
address = {Vienna, Austria},
year = {2016},
url = {https://www.R-project.org/},
}

We have invested a lot of time and effort in creating R, please cite it when using it for data analysis. See also ‘citation("pkgname")’ for citing R packages.

Quite verbose just to have R's name to appear right ?

From @djhurio's comment on an this answer using R, version does the trick too.