On Jan 7, 2004, at 10:37 AM, Steve Grazzini wrote: [..]
[..]I want to test whether STDIN (the default argument for -t) is hooked up to the terminal (which is what -t tells you) so that <ARGV> doesn't block waiting for user input.
I have absolutely no problem with the idea that one wants to use '-t' to establish that there is a controlling terminal, AKA a ttyline - but the problem is the false assumption that this is in some way associated with STDIN.
IF i am going to guard my code with '-t' to establish if there is any STDIN then as soon as the code is used inside of a forked and exec'd event where the child process is no longer attached to the TTYLINE then
foo | bar
will break because bar, failing to find it's controlling terminal will not see the information coming at it from foo through the STDIN pipe. So if one wanted to check that there were bits in STDIN, then one should do that with the IO::Select approach - since that will tell one if there are bits on STDIN, even if the process itself is being run without a controlling terminal.
To help illustrate the point:
<http://www.wetware.com/drieux/pbl/perlTrick/CommandLine/ got_ttyline.plx>
now granted, I have only tested this on darwin|freebsd|solaris|linux and only with perl 5.6 and 5.8 but they all come back with:
vladimir: 67:] perl got_ttyline.plx This Will Gin Up: Mother Got Back:hello, I am /tmp/drieux/CallMe.txt Mother Got Back:what tty line? Mother Got Back:STDIN says : /tmp/drieux/SomeCmd.txt:About to shout out Mother Got Back:STDIN says : sending var1 Mother Got Back:STDIN says : sending thing2 Mother Got Back:STDIN says : sending thing3 vladimir: 68:]
So it is possible that there are implementations of this which will not work in the way that I expect it - but as a general rule of thumb if one wants to know that one has a controlling terminal - "-t" then one should test for it. But simply because there is no controlling terminal does NOT mean that there is nothing on STDIN.
So that we are clear on this, it is not merely an issue in Perl, this is even MORE depressing when it is coded in a 'realCoderLanguage[dm]' and worse YET when the dilbert made TOTALLY irrational presumptions that if there was no controlling terminal that this of course meant that the build was suppose to use some WingNarkFrimFrimFrim library that of course leads to totally wacky problems when the build by hand at a terminal works find, and all of the code builds correctly but Blows Big Ones when done in an automated environment....
ciao drieux
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