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Check output device is a terminal: Difference between revisions
Check output device is a terminal (view source)
Revision as of 12:27, 15 February 2024
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[[Category:Initialization]]▼
{{task}}
▲[[Category:Hardware]]
▲[[Category:Terminal control]]
▲[[Category:Initialization]]
{{omit from|TI-83 BASIC|Output device is always either a terminal or created by the program}}▼
;Task:
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* [[Check input device is a terminal]]
<br><br>
=={{header|6502 Assembly}}==
{{works with|Commodore 64}}
<syntaxhighlight lang="6502asm">LDA $D011 ;screen control register 1
AND #%00100000 ;bit 5 clear = text mode, bit 5 set = gfx mode
BEQ isTerminal</syntaxhighlight>
=={{header|Ada}}==
{{works with|GNAT}}
We use the interface to C library functions <code>isatty()</code> and <code>fileno()</code>.
<
with Interfaces.C_Streams; use Interfaces.C_Streams;
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Put_Line(Standard_Error, "stdout is a tty.");
end if;
end Test_tty;</
{{out}}
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stdout is not a tty.
</pre>
=={{header|C}}==
Use <code>isatty()</code> on file descriptor to determine if it's a TTY. To get the file descriptor from a <code>FILE*</code> pointer, use <code>fileno</code>:
<
#include <stdio.h> // for fileno()
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: "stdout is not tty");
return 0;
}</
{{out}}
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stdout is not tty
</pre>
=={{header|C sharp|C#}}==
<
namespace CheckTerminal {
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}
}
}</
=={{header|C++}}==
{{trans|C}}
<
#include <io.h>
#define ISATTY _isatty
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return 0;
}</
=={{header|COBOL}}==
Works with GnuCOBOL.
<
*> istty, check id fd 0 is a tty
*> Tectonics: cobc -xj istty.cob
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goback.
end program istty.</
DISPLAY for fd 1 is directed to SYSERR to get some output during the various trials.
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fd 0 tty: +0000000000
fd 2 tty: +0000000000</pre>
=={{header|Common Lisp}}==
{{Works with|SBCL}}
<
(format T "stdout is~:[ not~;~] a terminal~%"
(interactive-stream-p s)))</
{{Out}}
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We use the interface to C library functions <code>isatty()</code> and <code>fileno()</code>. It needs to be compiled to be executed.
<
#include <sys/ioctl.h>
#include <unistd.h>
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(format T "stdout is~:[ not~;~] a terminal~%" (tty-p))
(quit)</
Compilation can be done with the following commands :
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$ ./is-tty | cat -
stdout is not a terminal</pre>
=={{header|Crystal}}==
<
File.new("/dev/tty").tty? #=> true
STDOUT.tty? #=> true</
=={{header|D}}==
<
extern(C) int isatty(int);
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void main() {
writeln("Stdout is tty: ", stdout.fileno.isatty == 1);
}</
{{out}}
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Stdout is tty: false
</pre>
=={{header|Factor}}==
You have to know 1 is the correct file descriptor number:
<
IN: scratchpad USE: unix.ffi
IN: scratchpad 1 isatty
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--- Data stack:
1
</syntaxhighlight>
=={{header|FreeBASIC}}==
<
Open Cons For Output As #1
' Open Cons abre los flujos de entrada (stdin) o salida (stdout) estándar
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Close #1
Sleep
</syntaxhighlight>
=={{header|Go}}==
Tells a ''terminal'' apart from a ''pipe'' on Linux and Mac, which is probably exactly what you need.
<
import (
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fmt.Println("Who are you? You're not a terminal")
}
}</
{{out}}
<pre>
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Who are you? You're not a terminal.
</pre>
=={{header|Haskell}}==
<
-- requires the unix package
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(if istty
then "stdout is tty"
else "stdout is not tty")</
{{Out}}
<pre>$ runhaskell istty.hs
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stdout is not tty
</pre>
=={{header|J}}==
<
Explanation:
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But, correctness requires us to keep in mind that these will only be heuristics, and will sometimes be incorrect (hopefully not often enough to matter a lot...).
=={{header|Javascript/NodeJS}}==
<
true</
=={{header|Julia}}==
<syntaxhighlight lang="julia">
if isa(STDOUT, Base.TTY)
println("This program sees STDOUT as a TTY.")
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println("This program does not see STDOUT as a TTY.")
end
</syntaxhighlight>
{{out}}
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This program sees STDOUT as a TTY.
</pre>
=={{header|Kotlin}}==
{{Works with|Ubuntu|14.04}}
<
import platform.posix.*
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else
println("stdout is not a terminal")
}</
{{out}}
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stdout is a terminal
</pre>
=={{header|Lua}}==
{{works with|Lua|5.1+}}
Using pure Lua, assuming a *NIX-like runtime environment ...
<
fd = tonumber( fd ) or 1
local ok, exit, signal = os.execute( string.format( "test -t %d", fd ) )
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print( "stdin", isTTY( 0 ) )
print( "stdout", isTTY( 1 ) )
print( "stderr", isTTY( 2 ) )</
{{out}}
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You can accomplish the same results using the luaposix [https://github.com/luaposix/luaposix] library:
<
local function isTTY ( fd )
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print( "stdin", isTTY( 0 ) )
print( "stdout", isTTY( 1 ) )
print( "stderr", isTTY( 2 ) )</
The output of this version is identical to the output of the first version.
=={{header|Nemerle}}==
There is no explicit way (ie <tt>isatty()</tt>)to do this; however, if we ''assume'' that standard out ''is'' a terminal, we can check if the output stream has been redirected (presumably to something other than a terminal).
<
=={{header|Nim}}==
Using function "isatty" of standard module "terminal" which accepts a File as argument.
As we want to redirect stdout, we write the messages on stderr.
<
stderr.write if stdout.isatty: "stdout is a terminal\n" else: "stdout is not a terminal\n"</
{{out}}
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<pre>Command: ./check_output_dev >somefile
Result: stdout is not a terminal</pre>
=={{header|OCaml}}==
<
print_endline (
if Unix.isatty Unix.stdout
then "Output goes to tty."
else "Output doesn't go to tty."
)</
Testing in interpreted mode:
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Output doesn't go to tty.
</pre>
=={{header|Ol}}==
<
(define (isatty? fd) (syscall 16 fd 19))
(print (if (isatty? stdout)
"stdout is a tty."
"stdout is not a tty."))
</syntaxhighlight>
=={{header|Perl}}==
The -t function on a filehandle tells you whether it's a terminal.
<
Terminal
$ perl -e "warn -t STDOUT ? 'Terminal' : 'Other'" > x.tmp
Other
</syntaxhighlight>
=={{header|Phix}}==
<!--<syntaxhighlight lang="phix">(notonline)-->
<span style="color: #008080;">without</span> <span style="color: #008080;">js</span> <span style="color: #000080;font-style:italic;">-- (no input or output redirection in a browser!)</span>
<span style="color: #7060A8;">printf</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">,</span><span style="color: #008000;">"stdin:%t, stdout:%t, stderr:%t\n"</span><span style="color: #0000FF;">,{</span><span style="color: #000000;">isatty</span><span style="color: #0000FF;">(</span><span style="color: #000000;">0</span><span style="color: #0000FF;">),</span><span style="color: #000000;">isatty</span><span style="color: #0000FF;">(</span><span style="color: #000000;">1</span><span style="color: #0000FF;">),</span><span style="color: #000000;">isatty</span><span style="color: #0000FF;">(</span><span style="color: #000000;">2</span><span style="color: #0000FF;">)})</span>
<!--</syntaxhighlight>-->
{{out}}
<pre>
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stdin:false, stdout:true, stderr:true
</pre>
=={{header|PHP}}==
<
if(posix_isatty(STDOUT)) {
echo "The output device is a terminal".PHP_EOL;
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echo "The output device is NOT a terminal".PHP_EOL;
}
</syntaxhighlight>
=={{header|Python}}==
Pretty much the same as [[Check input device is a terminal#Python]].
<
if stdout.isatty():
print 'The output device is a teletype. Or something like a teletype.'
else:
print 'The output device isn\'t like a teletype.'</
=={{header|Quackery}}==
{{trans|Python}}
<
to_stack( 1 if stdout.isatty() else 0)|
python ] is ttyout ( --> b )
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[ say "Looks like a teletype." ]
else
[ say "Not a teletype." ]</
{{out}}
<pre>Looks like a teletype.</pre>
=={{header|Racket}}==
<
(terminal-port? (current-output-port))
</syntaxhighlight>
=={{header|Raku}}==
(formerly Perl 6)
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$ raku -e 'note $*OUT.t' >/dev/null
False</pre>
=={{header|REXX}}==
{{works with|PC/REXX under DOS or in a DOS window under MS Windows}}
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<br>On IBM mainframes, a user can have STDIN defined, but the terminal can be ''disconnected''.
<
signal on syntax /*if syntax error, then jump ──► SYNTAX*/
say 'output device:' testSTDIN() /*displays terminal ──or── other */
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end /* [↑] can't use a RETURN here. */
/* ··· handle other REXX syntax errors here ··· */</
{{out|output|text= when using the default input:}}
<pre>
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output device: 6
</pre>
=={{header|Ruby}}==
<
p f.isatty # => false
p STDOUT.isatty # => true
</syntaxhighlight>
=={{header|Rust}}==
<
extern crate libc;
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println!("stdout is not tty");
}
}</
=={{header|Scala}}==
{{Works with|Ubuntu|14.04}}
<
object IsATty extends App {
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println("tty " + apply(true))
}</
=={{header|Standard ML}}==
<
=={{header|Swift}}==
<syntaxhighlight lang="swift">print(isatty(STDOUT_FILENO) != 0 ? "TTY" : "Not TTY" )</syntaxhighlight>
=={{header|Tcl}}==
To detect whether output is going to a terminal in Tcl, you check whether the <code>stdout</code> channel looks like a serial line (as those are indistinguishable from terminals). The simplest way of doing that is to see whether you can read the <tt>-mode</tt> or <code>-xchar</code> channel options, which are only present on serial channels:
<
puts [expr {$toTTY ? "Output goes to tty" : "Output doesn't go to tty"}]</
At the system call level, when Tcl is setting up the channels that correspond to the underlying <tt>stdout</tt> (and <tt>stdin</tt> and <tt>stderr</tt>) file descriptors, it checks whether the channels are network sockets (with <code>getsockname()</code>) or serial lines (with <code>isatty()</code>). This allows Tcl scripts to find out information about their calling environment (e.g., when they are run from <tt>inetd</tt>) with minimal code.
{{out|Demonstrating}}
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===Channel type discovery with older Tcl versions===
Before Tcl 8.4, this discovery process is impossible; <code>stdout</code> always looks like it is going to a file. With 8.4, you can discover the channel type but you need slightly different (and less efficient, due to the thrown error in the non-tty case) code to do it.
<
=={{header|UNIX Shell}}==
<
if [ -t 1 ]
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else
echo "Output is NOT a terminal" >/dev/tty
fi</
=={{header|Visual Basic .NET}}==
{{trans|C#}}
<
Sub Main()
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End Sub
End Module</
=={{header|Wren}}==
{{trans|C}}
As there is currently no way to obtain this information via Wren CLI, we instead embed a Wren script in a C application and ask the host program to get it for us.
<syntaxhighlight lang="wren">/* Check_output_device_is_a_terminal.wren */
class C {
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}
System.print("Output device is a terminal = %(C.isOutputDeviceTerminal)")</
<br>
We now embed this Wren script in the following C program, compile and run it.
<
#include <unistd.h>
#include <stdio.h>
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WrenVM* vm = wrenNewVM(&config);
const char* module = "main";
const char* fileName = "
char *script = readFile(fileName);
WrenInterpretResult result = wrenInterpret(vm, module, script);
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free(script);
return 0;
}</
{{out}}
<pre>
$ ./Check_output_device_is_a_terminal
Output device is a terminal = true
$ ./
$ cat tmp
Output device is a terminal = false
$ ./
Output device is a terminal = false
</pre>
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=={{header|zkl}}==
On Unix, check to see if stdout's st_mode is a character device.
<
fcn S_ISCHR(f){ f.info()[4].bitAnd(S_IFCHR).toBool() }
S_ISCHR(File.stdout).println();</
{{out}}
<pre>
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False
</pre>
▲{{omit from|TI-83 BASIC|Output device is always either a terminal or created by the program}}
|