Re^11: Need sleep walking help

Hi Marshall,

I just wanted to point out the -t operator that tests whether a filehandle is connected to a TTY. I don't know if this is the same mechanism that Perl uses to decide whether to use line-buffered mode or not, and I dimly remember reading somewhere that the -t test isn't always reliable, but anyway, this snippet would probably also confirm the issue.

$ perl -e 'warn "STDOUT ".(-t STDOUT?"IS":"is NOT")." a TTY\n"'
STDOUT IS a TTY
$ perl -e 'warn "STDOUT ".(-t STDOUT?"IS":"is NOT")." a TTY\n"' | cat
STDOUT is NOT a TTY
[download]

Regards,
-- Hauke D

Comment on Re^11: Need sleep walking help Select or Download Code

Replies are listed 'Best First'.
Re^12: Need sleep walking help by choroba (Cardinal) on Feb 04, 2017 at 16:55 UTC
> I dimly remember reading somewhere that the -t test isn't always reliable Probably in Perl::Critic::Policy::InputOutput::ProhibitInteractiveTest ? It doesn't say why, but it offers an alternative. ($q=q:Sq=~/;[c](.)(.)/;chr(-\|\|-\|5+lengthSq)`"S\|oS2"`map{chr \|+ord }map{substrSq`S_+\|`\|}3E\|-\|`7**2-3:)=~y+S\|`+$1,++print+eval$q,q,a, [download]	[reply] [d/l]
Re^13: Need sleep walking help by haukex (Archbishop) on Feb 06, 2017 at 08:51 UTC
Hi choroba, Probably in Perl::Critic::Policy::InputOutput::ProhibitInteractiveTest ? Yes, that was exactly it! It doesn't say why, but it offers an alternative. I checked PBP and that's the source (Chapter 10. I/O, Interactivity). However, it doesn't really say anything is broken with `-t`, just that "`-t ARGV && -t STDOUT`" shouldn't be used to determine if the program is connected to a terminal, as in whether the user can be prompted interactively or not. Interestingly, the recommended alternative, IO::Interactive, uses `-t` itself :-) Regards, -- Hauke D	[reply] [d/l] [select]