SPUG: Multiple uses of <STDIN> in a script?

Ryan Erwin ryan at erwin.org
Fri Oct 15 10:55:33 CDT 1999

Greetings once again Spuggers...
Back to yesterdays' question about STDIN...

I tried to issue:
$where = tell (STDIN);
seek(STDIN, $where, 0);
and a few other seek commands...
I tried 
STDIN->POSIX::clearerr;	# i think that was the syntax i used...

To No Avail...
my $var = open(TTY,"</dev/tty") || die "can't open </dev/tty $!";
did work, but it is very cumbersom to type what i want, press [enter] then pressCTRL+D to finish the input...

Here is a version of the script that shows the problem:
#!/usr/bin/perl -w

my @rray = <STDIN>;
chomp (@rray);
foreach (@rray) {
	print "this line is $_: [Y:N] "; 
	my $y_or_n = <STDIN>;	
	chomp ($y_or_n);
	print "$y_or_n just for the heck of it...\n";

I would run the script (i'll call it /tmp/test.pl) like this:
find /tmp | /tmp/test.pl

I think that this should work, but it doesn't...
Obviously, it doesn't work, so i'm doing (at least) something wrong, but i'm not sure what.  Please, I'm sure one of you knows how to make this work ;)

BTW: this is just the really, really minimized version of the script that just takes a list of files on STDIN and 2 regex's, one to filter the list sent to STDIN, one to make the new name for the file.  I thought it would be useful when i need to change the names of a bunch of files at once...  I would have posted it, but i forgot it at home and my PPP connection at home hasn't been working since i moved (last week).


ryan [ryan at erwin.org]

On Thu, 14 Oct 1999, Stuart Poulin wrote:

> One thing you can do on Unix is open /dev/tty for input.
> Then even if your program is reading STDIN from a file or a pipe it can get
> input from the user.
> open(TTY,"</dev/tty") or die "Can't open </dev/tty : $!";
> --- Ryan Erwin <ryan at erwin.org> wrote:
> > I hate to interrupt our fun discussion on where we are going to have our
> > meetings but i ran into a little problem yesterday and wondered if one of you
> > know the answer. ;) <- what do ya think of that guy...
> > 
> > Anyways:
> > i have a little command line script on my linux box that takes a list of file
> > names on <STDIN>, then asks the user (me) a question about the file. 
> > Usually, to get user input I just use my $somevar = <STDIN>; but it doesn't
> > work in this case.
> > 
> > i hunted around last night and found that perlfaq8 had a section called "Why
> > can't my script read from STDIN after I gave it EOF?"  This sounds exactally
> > like what is happening so I read on and the faq8 said "the POSIX module
> > defines clearerr() that you can use."  So I checked the POSIX mod docs and it
> > says:
> > clearerr - use IO::Handle::clearerr() instead.
> > Now, I go over and check IO::Handle docs and find that I'm supposed to issue:
> > $fh->clearerr
> > I do this (STDIN->clearerr) and it works just find, but I still can't prompt
> > the user for something on STDIN.
> > 
> > The faq8 says that this is the technically correct way to reset the err flag
> > so I would like to use it.  Besides, seek on STDIN just seems strange to me
> > (if it would even work, i haven't tried).
> > 
> > Thanks!
> > 
> > ryan [ryan at erwin.org]

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