A) (not really what you want)

sub interactive {
return -t STDIN && -t STDOUT
}

The file test operator -t tells you if the filehandle is a tty or not.
But, if you use it in a program whose STDIN/STDOUT are redirected, even if
called from cmdline, the sub returns false. Called by cron, it returns also
false.


B) Maybe what you want, if you use a POSIX compliant system
(there may be better solutions or even a module):

# has the prog control over its tty?
# returns true even if STDIN/STDOUT are redirected;
# returns false if called by cron
# (see man POSIX)
# [tested]
#
use POSIX qw/getpgrp tcgetpgrp/;
sub controls_tty {
local *TTY;
open TTY, "/dev/tty" or die "error opening tty: $!";
my $tpgrp=tcgetpgrp(fileno(TTY));
my $pgrp =getpgrp();
close TTY or warn "error closing tty: $!";
return ($tpgrp==$pgrp);
}

# returns true if run under CGI
# since the server defines GATEWAY_INTERFACE
# [untested]
#
sub from_cgi {
return $ENV{GATEWAY_INTERFACE}=~/^CGI/o ? 1 : 0;
}

# check between three cases:
# [untested]
#
if (from_cgi()) {
print "called by CGI";
}
elsif (controls_tty) {
print "called from cli";
}
else {
print "called from cron (e.g.?)";
}


corrections from others are welcome :-)

greetings joe

Concerning ActivePerl under Windows I don't know
(I suppose the POSIX-Code didn't run under Windows? - maybe there is a Module
from Activestate or on CPAN (http://search.cpan.org) ?)

Apart from that, you have to check in your output producing code the current
invocation "kind" (sorry for my bad english / see my previous answer) and
produce the output accordingly.

Eventually, you could produce the output in html and then use a module wich
strips the text from the html for text output - not the most efficient way
though. I think the best way depends also on the complexity of the html and on
layout requirements of the plain text output.

hope this helps a bit, otherwise somebody else could eventually provide some
more specific help?

grettings joe

P.S.: I must admit that I'm not a specialist in platform independent code :-(