Multiline shebang: Difference between revisions

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{{draft task|Basic language learning}}
 
Simple shebangs can help with scripting, e.g., <code>#!/usr/bin/env python</code> at the top of a Python script will allow it to be run in a terminal as "<code>./script.py</code>".
 
Line 10 ⟶ 11:
;See also
* [[Native shebang]] - where the "program loaded" is ''of'' the actual native task language.
<br><br>
 
=={{header|Ada}}==
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{{trans|C}}
 
<langsyntaxhighlight Adalang="ada">#!/bin/bash
sed -n -e '7,$p' < "$0" > mulshbang.adb
gnatmake -q mulshbang
Line 31 ⟶ 33:
Ada.Command_Line.Argument(I));
end loop;
end Mulshbang;</langsyntaxhighlight>
 
{{out}}
Line 80 ⟶ 82:
The namespace = basename = filename minus the extension must be passed as a value to Clojure's -m flag.
 
<langsyntaxhighlight lang="clojure">":";exec clj -m `basename $0 .clj` $0 ${1+"$@"}</langsyntaxhighlight>
 
Alternate shebang, using the [https://github.com/kumarshantanu/lein-exec Leiningen 'exec' plugin]:
 
<langsyntaxhighlight lang="clojure">":";exec lein exec $0 ${1+"$@"}</langsyntaxhighlight>
 
=={{header|Common Lisp}}==
Line 92 ⟶ 94:
Here, the script name is passed once to CLISP and once to ext:*args*, which normally omits it.
 
<langsyntaxhighlight lang="lisp">#!/bin/sh
#|
exec clisp -q -q $0 $0 ${1+"$@"}
|#</langsyntaxhighlight>
 
=={{header|E}}==
Line 103 ⟶ 105:
In this example, we are including the command name itself in the argument list, which would ordinarily not include it.
 
<langsyntaxhighlight lang="e">#!/bin/sh
>/dev/null; exec rune $0 $0 ${1+"$@"}
 
println(`I was called as ${interp.getArgs()[0]}.`)</langsyntaxhighlight>
 
=={{header|Emacs Lisp}}==
<langsyntaxhighlight lang="lisp">:;exec emacs -batch -l $0 -f main $*</langsyntaxhighlight>
 
=={{header|Erlang}}==
Line 115 ⟶ 117:
hello.erl
 
<langsyntaxhighlight Erlanglang="erlang">#!/usr/bin/env escript
 
-module(hello).
-export([main/1]).
 
main(_) -> io:format("Hello World!~n", []).</langsyntaxhighlight>
 
This works fine when the module is run by itself with dot slash:
 
<langsyntaxhighlight lang="sh">$ ./hello.erl
Hello World!</langsyntaxhighlight>
 
But when another Erlang module tries to import the code, or you try to compile manually in erl, you get a syntax error.
 
<langsyntaxhighlight lang="sh">$ erl
Erlang R14B03 (erts-5.8.4) [source] [64-bit] [smp:2:2] [rq:2] [async-threads:0] [hipe] [kernel-poll:false]
 
Line 136 ⟶ 138:
./hello.erl:1: syntax error before: '#'
./hello.erl:4: no module definition
error</langsyntaxhighlight>
 
=={{header|F Sharp|F#}}==
Line 142 ⟶ 144:
F# scripts may be run with dot-slash notation using the following multiline shebang:
 
<langsyntaxhighlight lang="f#">#light (*
exec fsharpi --exec "$0" --quiet
*)
 
let main = printfn "Hello World"</langsyntaxhighlight>
 
However, if a script has any dependencies that need to be compiled in, the fsharpi interpreter will not understand how to import them. This means dot-slashing is no longer viable, and the script must be compiled in order to run properly. The shebang can stay, but it is best to remove it, to make clear to users that the script should not be dot-slashed.
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Factor no longer requires a space after <code>#!</code> as of v0.95.
 
<langsyntaxhighlight lang="factor">#!/usr/bin/env factor -script</langsyntaxhighlight>
 
=={{header|Forth|Gforth}}==
We can use Gforth's (non-ANS standard) support for shebangs and the '#' number prefix to make Gforth skip over the shebang without interfering with shell script interpretation.
 
<langsyntaxhighlight lang="forth">#! /bin/sh
#0 [IF] \ lines below read by shell but ignored by Gforth
exec gforth \
Line 166 ⟶ 168:
[THEN]
.( hello world) CR BYE
</syntaxhighlight>
</lang>
 
=={{header|FreeBASIC}}==
FreeBASIC is a compiled, uninterpreted language, so it cannot be run directly from the Unix command line with a shebang.
 
However, you can create a shell script that compiles and runs your FreeBASIC program. Here I show an example:
 
<syntaxhighlight lang="vbnet">
#!/bin/bash
# Compile the FreeBASIC program
fbc myprogram.bas
# Run the compiled program
./myprogram
</syntaxhighlight>
 
In this script, myprogram.bas is a FreeBASIC program. When you run this shell script, it will compile the FreeBASIC program and then run it.
 
=={{header|Go}}==
<langsyntaxhighlight lang="go">#!/bin/bash
sed -n -e '12,$p' < "$0" > ttmmpp.go
go build ttmmpp.go
Line 195 ⟶ 212:
}
}
</syntaxhighlight>
</lang>
 
=={{header|Groovy}}==
<syntaxhighlight lang="groovy">#!/bin/bash
script_dir="$(cd $(dirname $0) >/dev/null; pwd -P)"
 
if [ -z "${GROOVY_HOME}" ]
then
echo 'GROOVY_HOME must be defined.' >&2
exit 1
fi
 
CLASSPATH="${script_dir}" "${GROOVY_HOME}/bin/groovy" -e "$(sed -e '1,/^!#$/d' $0)" "${@:1}"
exit
!#
println 'aoeu'
</syntaxhighlight>
 
=={{header|Haskell}}==
 
{{trans|C}}
 
<syntaxhighlight lang="haskell">#!/bin/bash
sed -n -e '7,$p' < "$0" > $0.$$.hs
ghc $0.$$.hs > /dev/null
./$0.$$ "$0" "$@"
rm $0.$$*
exit
import Text.Printf
import System.Environment
 
main :: IO ()
main = getArgs >>= mapM_ (uncurry $ printf "argv[%d] -> %s\n") . zip ([0..] :: [Int])</syntaxhighlight>
 
{{out}}
 
<pre>$ ./multibang.hs
argv[0] -> ./multibang.hs
$ ./multibang.hs Goodbye, World!
argv[0] -> ./multibang.hs
argv[1] -> Goodbye,
argv[2] -> World!</pre>
 
Or you can 'cheat' by ignoring Bash's complaints about Haskell comments (gives the exact same output as above):
 
<syntaxhighlight lang="haskell">#!/bin/bash
{- 2> /dev/null
exec runghc $0 $0 $@
-}
import Text.Printf
import System.Environment
 
main :: IO ()
main = getArgs >>= mapM_ (uncurry $ printf "argv[%d] -> %s\n") . zip ([0..] :: [Int])</syntaxhighlight>
 
=={{header|J}}==
 
Assuming this task is asking for a mix of unix shell commands and J, and also that the J binary directory is listed in <code>$PATH</code>
 
<langsyntaxhighlight Jlang="j">#!/bin/sh
# 0 :0
echo unix shell commands go here
echo presumably this will condition the environment
echo for example:
cd working-directory
echo or maybe you want to modify $PATH, ... whatever...
echo then start up J:
exec jconsole "$0" "$@"
)
 
NB. exit on error
onfailonfail_z_=:3 :0
1!:2&2 ARGV
1!:2&2]13!:12'' NB. display error message
Line 227 ⟶ 297:
echo p:i. 3 4
exit 0
</syntaxhighlight>
</lang>
 
'''Notes:'''
 
The <code>#!/bin/sh</code> line is interpreted by J as a verb train with no arguments - in other words, it is ignored.
 
The <code># 0 :0</code> line is interpreted by shell as a comment and by J as the beginning of a multiline "hereis" script which basically ignores everything up to the lone right parenthesis.
 
So then it's just regular shell script up until the line where we turn control over to J. On that line, we use <code>exec</code> (so that the shell process does not hang around, waiting for J to finish - J takes over the current process). And we pass any shell script command line arguments on to J.
 
On the J side of the fence, we presumably want this code to behave like a normal unix module, so we need to override J's default behavior (which is to provide the J command line). <code>9!:29]1[9!:27'2!:55]1</code> is a bit of magic that accomplishes that: it stacks a command to exit with exit code 1 to be executed when we reach the command line. So any errors will terminate the program.
 
Next, we run the system J profile so that we have all of the standard stuff that that provides. (Or leave this out if that's what you want.)
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Here's a variant where the shell script tests J's exit code and does something different based on success or failure.
 
<langsyntaxhighlight Jlang="j">#!/bin/sh
# 0 :0
echo unix shell commands go here
echo presumably this will condition the environment
echo for example:
cd working-directory
echo or maybe you want to modify $PATH, ... whatever...
echo then start up J:
if jconsole -jprofile "$0" "$@"; then
echo success
else
echo failure
fi
exit $?
)
 
Line 270 ⟶ 340:
echo p:i. 3 4
exit 0
</syntaxhighlight>
</lang>
 
The <code>exit $?</code> line tells the shell interpreter to ignore the J part of the file, and the <code>$?</code> reuses J's exit code as the exit code from the shell instance.
 
Note that we've left off the onfail handler within J, and just used a minimal definition to give us a non-zero exit code for the error case. Mostly, the assumption here would be that the error message would not be interesting, and that any failure should be handled by a retry. But you could replace the exit on error line here with the full definition and <code>9!:</code> preparatory bit from the previous example and you could also of course change the <code>1!:2&2</code> lines (<code>1!:2&2</code> is the "low-level" write to stdout mechanism for J - and, yes, those numbers are part of the definition of the language - or at least the "Foreigns" part of the language - note that ultimately all computer languages resolve to things which can be thought of as numbers or sequences of numbers, though some people will vigorously assert other things).
 
=={{header|jq}}==
 
Here is an example using bash:
<pre>
#!/bin/bash
# this line is ignored by jq provided it ends with a backslash \
exec jq -nef "$0" "$@"
# jq code follows
true
</pre>
 
Notice the trailing `\` at the end of the second line.
 
Arguments can be passed in to the script, e.g. using the --arg NAME VALUE option.
 
The above script will also work with `sh` provided the quotation marks around `$@` are removed.
 
=={{header|Julia}}==
<syntaxhighlight lang="julia">
#!/bin/sh
#=
echo Julia will ignore as commented all text between #= and =#
echo which allows us to place arbitrary unix shell code here
echo perhaps to change environment settings for Julia or
echo set the directory prior to starting the Julia program.
echo for example:
cd /user/meeting/working
echo then start the Julia program
exec julia "$0" "$@"
# comments ignored by Julia end here --> =#
 
function countto(n)
i = zero(n)
println("Counting to $n...")
while i < n
i += 1
end
println("Done!")
end
 
@time countto(10^10)
</syntaxhighlight>
 
=={{header|MATLAB}}==
 
Unlike Octave, MATLAB has no built-in support for shebangs. In fact, several tricks are required to even approximate a shebang, due to the byzantine way that MATLAB structures scripts and function files.
 
~/bin/shmatlab%:
 
<syntaxhighlight lang="bash">#!/bin/sh
matlab -nojvm -nodisplay -nosplash -r "varargin = regexp('${1+"$@"}', ' ', 'split'); nvarargin = length(varargin); run('$1'); exit" | tail -n +16
</syntaxhighlight>
 
args.m:
 
<syntaxhighlight lang="matlab">'shmatlab'% $0 ${1+"$@"}
'exit';
 
for i = 1:nvarargin
disp(varargin{i});
end</syntaxhighlight>
 
Example:
 
<pre>
$ ./args.m a b c
./args.m
a
b
c
</pre>
 
=={{header|Nim}}==
In Nim, multiline comments start with <code>#[</code> and end with <code>]#</code>. This allows to build a polyglot program which can be run as a shell script and compiled as a Nim program.
 
<syntaxhighlight lang="nim">#!/bin/bash
#[
echo Put here code to run as a shell script.
exit # This is needed to ignore last part of the file.
]#
 
# Nim program
echo "Executing Nim program"</syntaxhighlight>
 
=={{header|OCaml}}==
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ocamlc hates shebangs, so much trickery is needed. The number of underscores in the dummy kkkk identifier corresponds to the number of bash strings in the shebang. Thus, core library .cma files can be specified this way in interpreted mode, though accessing other OCaml scripts requires compiling them first, and referencing the .cmo's here.
 
<langsyntaxhighlight lang="ocaml">if true then ignore begin let kkkk _ _ _ _ = 0 in kkkk
"exec" "ocaml" "$0" "$@" + let fi = 0 and exit _ _ = 0 in if false
then exit
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end;;
 
let main = print_endline "Hello World!"</langsyntaxhighlight>
 
Example:
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=={{header|PARI/GP}}==
The PARI equivalent to a multiline shebang is a collection of <code>GP;</code> lines:
<syntaxhighlight lang="c">/*
<lang C>/*
GP;install("C_function_name","G","GP_name","./filename.gp.so");
GP;addhelp(GP_name, "GP_name(n): Computes the foo of bar(n).");
*/</langsyntaxhighlight>
These commands are passed to GP when invoked by gp2c.
 
=={{header|Perl}}==
From <code>perldoc perlrun</code>, the following is supposed to find perl one way or another under sh, csh or perl.
<langsyntaxhighlight lang="perl">#!/usr/bin/perl
eval '(exit $?0)' && eval 'exec perl -wS $0 ${1+"$@"}'
& eval 'exec /usr/bin/perl -wS $0 $argv:q'
if $running_under_some_shell;</langsyntaxhighlight>
 
=={{header|Perl 6}}==
=={{header|Phix}}==
<lang perl6>#!/usr/local/bin/perl6
Obviously this is not pwa/p2js compatible, since you cannot run bash or sed (with redirection) or phix or 'rm tmp.eu' from within a browser, and is only intended to be run on Linux, though you could perhaps run it on Windows but only in some kind of bash shell.
eval '(exit $?0)' && eval 'exec perl6 $0 ${1+"$@"}'
<!--<syntaxhighlight lang="phix">-->
& eval 'exec perl6 $0 $argv:q'
<span style="color: #000000;">#!/bin/bash
if 0;</lang>
sed -n -e '7,$p' < "$0" > tmp.eu
\path\to\phix tmp.eu "$@"
STATUS=$?
rm tmp.eu
exit $STATUS</span>
<span style="color: #008080;">without</span> <span style="color: #008080;">js</span> <span style="color: #000080;font-style:italic;">-- (not that pwa/p2js would get this far!)</span>
<span style="color: #0000FF;">?</span><span style="color: #7060A8;">command_line</span><span style="color: #0000FF;">()</span>
<!--</syntaxhighlight>-->
Alternatively it was not particularly difficult, just for this task, to add #[ and #] handling, just like /* and */, to both desktop/Phix and pwa/p2js.<br>
Note that I simply cannot see how #! ... !# could ever work, in any programming language, that is while also allowing single line shebangs with no closing !#.<br>
Hence the following (partly based on the Julia entry) now (1.0.2) also works fine, with no detrimental (or beneficial) effect either on (standard) Windows or under pwa/p2js:
<!--<syntaxhighlight lang="phix">(phixonline)-->
<span style="color: #00000;font-style:italic;">#!/bin/bash
#[
echo Phix ignores all text between #[ and #] in exactly the same way as /* and */
echo (both "and" are nested comments), allowing arbitrary shell code, for example
cd /user/project/working
exec /path/to/phix "$0" "$@"
exit # may be needed for the shell to ignore the rest of this file.
# comments ingored by Phix end here -&gt; #]</span>
<span style="color: #008080;">with</span> <span style="color: #008080;">javascript_semantics</span>
<span style="color: #7060A8;">puts</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"This is Phix code\n"</span><span style="color: #0000FF;">)</span>
<!--</syntaxhighlight>-->
 
=={{header|PicoLisp}}==
We can use a multi-line comment #{ ... }# to hide the shell commands from Lisp. The opening #{ in turn is a coment for the shell.
<langsyntaxhighlight PicoLisplang="picolisp">#!/bin/bash
#{
exec pil $0 foo bar
Line 334 ⟶ 513:
# Lisp code
(println (cadr (file)) (opt) (opt))
(bye)</langsyntaxhighlight>
{{out}}
<pre>$ ./myScript
Line 341 ⟶ 520:
=={{header|Pike}}==
we use a multiline comment to hide the shell command from pike, and we can use a preprocessor directive to hide the comment begin from the shell.
<langsyntaxhighlight Pikelang="pike">#!/bin/bash
#define foo foo /*
exec pike $0 hello world
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{
write("%O\n", argv);
}</langsyntaxhighlight>
 
{{out}}
Line 362 ⟶ 541:
This style of shebang would also work with other languages that use double dashes for comments, though most of them (Lua, Haskell) already support traditional #!... shebangs.
 
<langsyntaxhighlight lang="postgresql">--() { :; }; exec psql -f "$0"
 
SELECT 'Hello World!';</langsyntaxhighlight>
 
=={{header|Python}}==
We can use multiple strings to make the shell commands do nothing from Python (actually they become the module docstring.).
<langsyntaxhighlight Pythonlang="python">#!/bin/bash
"exec" "python" "$0"
 
print "Hello World"</langsyntaxhighlight>
{{out}}
<pre>$ ./myScript
Line 378 ⟶ 557:
Control structures (if/for/etc.) can't be quoted,
but one can use the following to embed any script:
<langsyntaxhighlight Pythonlang="python">#!/bin/sh
"true" '''\'
if [ -L $0 ]; then
Line 388 ⟶ 567:
__doc__ = """module docstring"""
 
print "Hello World"</langsyntaxhighlight>
 
Here we use a) the code <nowiki>'''\'</nowiki> translates to \ in shell, but opens a multi-line string in Python; b) the true command ignores its argument, c) we always exit before the ending <nowiki>'''</nowiki> so that the shell interpreter never reads it. Also, remember to set any docstrings by assigning to __doc__ since the docstring is already used for the shell script.
 
=={{header|Racket}}==
<syntaxhighlight lang="racket">
<lang Racket>
#!/bin/sh
#| -*- scheme -*-
Line 407 ⟶ 586:
(printf "argument: ~a\nexecuted as: ~a\n"
arg (find-system-path 'exec-file)))
</syntaxhighlight>
</lang>
 
=={{header|Raku}}==
(formerly Perl 6)
 
<syntaxhighlight lang="raku" line>#!/usr/local/bin/raku
use MONKEY; EVAL '(exit $?0)' && EVAL 'exec rake $0 ${1+"$@"}'
& EVAL 'exec raku $0 $argv:q'
if 0;</syntaxhighlight>
 
=={{header|Ruby}}==
Line 416 ⟶ 603:
This script works both ways: either <code>/bin/sh script.rb</code> or <code>ruby script.rb</code> would run multiple lines of shell commands, and then start Ruby.
 
<langsyntaxhighlight lang="ruby">#!/bin/sh
 
# Insert shell code here!
Line 438 ⟶ 625:
ARGV.each_with_index do |arg, i|
puts " ARGV[#{i}]: #{arg}"
end</langsyntaxhighlight>
 
When running <code>/bin/sh scratch.rb</code>, the shell:
Line 458 ⟶ 645:
The scalac compiler does not.
 
<langsyntaxhighlight lang="scala">
#!/bin/bash
FOO=bar
Line 474 ⟶ 661:
}
 
println("fact(5) = " + fact(5));</langsyntaxhighlight>
 
=={{header|Scheme}}==
{{works with|Chicken Scheme}}
 
<langsyntaxhighlight lang="scheme">#!/usr/bin/env csi -ss</langsyntaxhighlight>
 
=={{header|Sidef}}==
<syntaxhighlight lang="ruby">#!/bin/sh
 
#`(if running under some shell) {
eval 'exec /usr/bin/sidef $0 ${1+"$@"} "world"'
}
 
say "Hello, #{ARGV[0]}!"</syntaxhighlight>
 
{{out}}
<pre>
$ ./script.sf
Hello, world!
 
$ ./script.sf Sidef
Hello, Sidef!
 
$ sidef script.sf RosettaCode
Hello, RosettaCode!
</pre>
 
=={{header|Smalltalk}}==
<langsyntaxhighlight lang="smalltalk">"exec" "gst" "-f" "$0" "$0" "$@"</langsyntaxhighlight>
 
=={{header|SQL PL}}==
{{works with|Db2 LUW}}
Based on the Postgres shebang, it works the same with IBM Db2.
 
<syntaxhighlight lang="sql pl">
--() { :; }; exec db2 -txf "$0"
 
get instance;
connect to sample;
select 'Hello' from sysibm.sysdummy1;
values current date;
</syntaxhighlight>
Output:
<pre>
$ ./myScript
 
The current database manager instance is: db2inst1
 
 
 
Database Connection Information
 
Database server = DB2/LINUXX8664 11.1.1
SQL authorization ID = DB2INST1
Local database alias = SAMPLE
 
 
Hello
 
04/22/2018
</pre>
 
The db2profile should be loaded before executing the 'db2' command (. ~db2inst1/sqllib/db2profile).
 
The options used in the example are: t - delimited by semi colon, x - Suppress printing of column headings, f - Read from input file. For other options, you can execute 'db2 ? options', and change the shebang.
 
=={{header|Tcl}}==
It is normal to use a line like this:
<syntaxhighlight lang ="tcl">#!/usr/bin/env tclsh</langsyntaxhighlight>
But in cases where that is not enough perhaps because it needs some logic to locate the Tcl interpreter to use the differences in the way Tcl and the Bourne shell interpret end-of-line backslashes in comments can be used:
<langsyntaxhighlight lang="tcl">#!/bin/sh
# Next line is comment in Tcl, but not in sh... \
exec tclsh "$0" ${1+"$@"}</langsyntaxhighlight>
Additional complexity can be added so long as the lines for the shell are commented in a Tcl sense.
 
Line 515 ⟶ 759:
arg[3]="3"
$</pre>
 
=={{header|Wren}}==
Wren doesn't support multiline shebangs as such. Anything after the first line is always interpreted as Wren code.
 
You can get around this by placing shell commands in a block comment after a single line shebang. So (ignoring the strange error message) the following works:
<syntaxhighlight lang="wren">#!/bin/bash
/*
echo "Hello from bash"
/bin/wren Multiline_shebang.wren
exit
*/
System.print("Hello from Wren")</syntaxhighlight>
 
{{out}}
<pre>
$ chmod +x Multiline_shebang.wren
$ ./Multiline_shebang.wren
./Multiline_shebang.wren: line 2: /bin: Is a directory
Hello from bash
Hello from Wren
</pre>
<br>
However, we don't actually need a multiline shebang to get the script name as this is always passed automatically as the second command line argument when the Wren process is spawned, the first argument being the Wren executable itself. Moreover, if a single line shebang is used, the third argument will be the shell command used to execute the script.
<syntaxhighlight lang="wren">#!/bin/wren Multiline_shebang_2.wren
import "os" for Process
 
var args = Process.allArguments
System.print("Executable : %(args[0])")
System.print("Script name : %(args[1])")
System.print("Shell command : %(args[2])")
if (args.count > 3) {
for (i in 3...args.count) System.print("Argument %(i-2) : %(args[i])")
}</syntaxhighlight>
 
{{out}}
<pre>
$ chmod +x Multiline_shebang_2.wren
$ ./Multiline_shebang_2.wren one two three
Executable : /bin/wren
Script name : Multiline_shebang_2.wren
Shell command : ./Multiline_shebang_2.wren
Argument 1 : one
Argument 2 : two
Argument 3 : three
</pre>
 
=={{header|zkl}}==
Line 520 ⟶ 809:
 
File foo.zkl (the .zkl extension is needed):
<langsyntaxhighlight lang="zkl">#!/bin/sh
#<<<#
echo "A shell script in a zkl program ($0)"
Line 527 ⟶ 816:
exit
#<<<#
println("The shell script says ",Systemvm.argv[2,*]arglist.concat(" "));</langsyntaxhighlight>
{{out}}
<pre>
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