Check output device is a terminal: Difference between revisions

stdout is not a terminal</pre>

{{Works with|ECL}}

We use the interface to C library functions <code>isatty()</code> and <code>fileno()</code>. It needs to be compiled to be executed.

<lang lisp>(ffi:clines "

#include <sys/ioctl.h>

#include <unistd.h>

int ttyPredicate() {

return isatty(fileno(stdout));

}")

(ffi:def-function

("ttyPredicate" c-ttyp)

() :returning :int)

(defun tty-p()

(if (= 1 (c-ttyp))

t

nil))

(format T "stdout is~:[ not~;~] a terminal~%" (tty-p))

(quit)</lang>

Compilation can be done with the following commands :

<code>ecl --eval '(compile-file "file.lisp" :system-p t)' --eval '(quit)'</code>

<code>ecl --eval '(c:build-program "is-tty" :lisp-files (list "file.o"))' --eval '(quit)'</code>

{{Out}}

<pre>$ ./is-tty

stdout is a terminal

$ ./is-tty | cat -