Check output device is a terminal: Difference between revisions

=={{header|COBOL}}==

Works with GnuCOBOL.

<lang cobol> *>

*> istty, check id fd 0 is a tty

*> Tectonics: cobc -xj istty.cob

*> echo "test" | ./istty

*>

identification division.

program-id. istty.

data division.

working-storage section.

01 rc usage binary-long.

procedure division.

sample-main.

call "isatty" using by value 0 returning rc

display "fd 0 tty: " rc

call "isatty" using by value 1 returning rc

display "fd 1 tty: " rc upon syserr

call "isatty" using by value 2 returning rc

display "fd 2 tty: " rc

goback.

end program istty.</lang>

DISPLAY for fd 1 is directed to SYSERR to get some output during the various trials.

{{out}}

<pre>prompt$ cobc -xj istty.cob

fd 0 tty: +0000000001

fd 1 tty: +0000000001

fd 2 tty: +0000000001

prompt$ echo "test" | ./istty

fd 0 tty: +0000000000

fd 1 tty: +0000000001

fd 2 tty: +0000000001

prompt$ echo "test" | ./istty >/dev/null

fd 1 tty: +0000000000

prompt$ echo "test" | ./istty 2>/dev/tty

fd 0 tty: +0000000000

fd 1 tty: +0000000001

fd 2 tty: +0000000001

prompt$ echo "test" | ./istty 2>/dev/null

fd 0 tty: +0000000000

fd 2 tty: +0000000000</pre>