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comp.lang.ruby

Newbie needs help getting user input

Peter Vanderhaden

9/30/2007 1:29:00 AM

I'm trying to learn Ruby and trying to convert a Perl program at the
same time. I need to prompt a user to enter a number to select a
processing option. In Perl, I did it this way:

#
print STDERR "Enter option: ";
chomp ($option = <STDIN>);
#

I've searched the web and several books, but I haven't found anything
that works. It also seems that my system doesn't recognize "gets". Can
anyone help me out, and maybe post a simple input routine I can look at?
Thanks....
--
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12 Answers

Peter Vanderhaden

9/30/2007 1:55:00 AM

0

Wayne,
Thanks for the answer. The only problem is that I'm using Windows, not
Unix. I'm having problems with gems in Windows.
PV

Wayne E. Seguin wrote:
> Peter,
> $ gem install highline
>
>
>> require "highline"
>> option = Highline.new.ask("Enter option: ")
>
> There are many more things you can do with this gem, check out HighLine:
> http://highline.ruby...
>
>
> I hope this helps,
>
> ~Wayne

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7stud 7stud

9/30/2007 2:32:00 AM

0

Peter Vanderhaden wrote:
> I'm trying to learn Ruby and trying to convert a Perl program at the
> same time. I need to prompt a user to enter a number to select a
> processing option. In Perl, I did it this way:
>
> #
> print STDERR "Enter option: ";
> chomp ($option = <STDIN>);
> #
>

print "Enter option (1, 2, 3): "
input = gets.chomp

if input == '1'
puts "I'm executing option 1."
elsif input == '2'
puts "I'm executing option 2."
elsif input == '3'
puts "I'm executing option 3."
else
puts "Bad input."
end


Or:

print "Enter option (1, 2, 3): "
input = gets.chomp

case input
when '1'
puts "I'm executing option 1."
when '2'
puts "I'm executing option 2."
when '3'
puts "I'm executing option 3."
else
puts "Bad input."
end

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John Joyce

9/30/2007 2:36:00 AM

0


On Sep 29, 2007, at 8:28 PM, Peter Vanderhaden wrote:

> I'm trying to learn Ruby and trying to convert a Perl program at the
> same time. I need to prompt a user to enter a number to select a
> processing option. In Perl, I did it this way:
>
> #
> print STDERR "Enter option: ";
> chomp ($option = <STDIN>);
> #
>
> I've searched the web and several books, but I haven't found anything
> that works. It also seems that my system doesn't recognize
> "gets". Can
> anyone help me out, and maybe post a simple input routine I can
> look at?
> Thanks....
> --
> Posted via http://www.ruby-....
>
The usual basic thing is:

puts "Enter option:"
option = gets.chomp


If your system isn't recognizing gets, then you've got some other
problem that should be fixed before writing much code.

Sebastian Hungerecker

9/30/2007 8:43:00 AM

0

Peter Vanderhaden wrote:
> print STDERR "Enter option: ";

The ruby equivalent of this would be STDERR.print "Enter option: " but why
STDERR? That hardly looks like an error message to me.

> chomp ($option = <STDIN>);

That would be gets.chomp or STDIN.gets.chomp if you want to make sure that
you read from STDIN.

> I've searched the web and several books, but I haven't found anything
> that works. It also seems that my system doesn't recognize "gets".

Your system is not supposed to recognize gets. If your ruby does not recognize
gets, there is something seriously wrong with your ruby installation.


HTH,
Sebastian
--
Jabber: sepp2k@jabber.org
ICQ: 205544826

Peter Vanderhaden

9/30/2007 1:47:00 PM

0

Sebastian,
My Ruby installation must be corrupt, as it doesn't recognize gets.
When I try your solution, I get the following error message:

D:/scripts/ruby/f0.rb:10:in `gets': Bad file descriptor (Errno::EBADF)
from D:/scripts/ruby/f0.rb:10

I'd assume the best way to correct this would be to reinstall Ruby?
Would you agree?

Thanks,
PETERV


Sebastian Hungerecker wrote:

> Peter Vanderhaden wrote:
>> print STDERR "Enter option: ";
>
> The ruby equivalent of this would be STDERR.print "Enter option: " but
> why
> STDERR? That hardly looks like an error message to me.
>
>> chomp ($option = <STDIN>);
>
> That would be gets.chomp or STDIN.gets.chomp if you want to make
> sure that
> you read from STDIN.
>
>> I've searched the web and several books, but I haven't found anything
>> that works. It also seems that my system doesn't recognize "gets".
>
> Your system is not supposed to recognize gets. If your ruby does not
> recognize
> gets, there is something seriously wrong with your ruby installation.
>
>
> HTH,
> Sebastian

--
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Peter Vanderhaden

9/30/2007 2:07:00 PM

0

Sebastian,
FYI, the reason I'm sending the prompt to STDERR instead of STDOUT is
that I've used reopen to redirect STDOUT to a file. I did that because
I want to write data to a file. I'm new to this, so if there's a better
way to write to the file, I'm all ears :)
PETERV

Peter Vanderhaden wrote:
> Sebastian,
> My Ruby installation must be corrupt, as it doesn't recognize gets.
> When I try your solution, I get the following error message:
>
> D:/scripts/ruby/f0.rb:10:in `gets': Bad file descriptor (Errno::EBADF)
> from D:/scripts/ruby/f0.rb:10
>
> I'd assume the best way to correct this would be to reinstall Ruby?
> Would you agree?
>
> Thanks,
> PETERV
>
>
> Sebastian Hungerecker wrote:
>
>> Peter Vanderhaden wrote:
>>> print STDERR "Enter option: ";
>>
>> The ruby equivalent of this would be STDERR.print "Enter option: " but
>> why
>> STDERR? That hardly looks like an error message to me.
>>
>>> chomp ($option = <STDIN>);
>>
>> That would be gets.chomp or STDIN.gets.chomp if you want to make
>> sure that
>> you read from STDIN.
>>
>>> I've searched the web and several books, but I haven't found anything
>>> that works. It also seems that my system doesn't recognize "gets".
>>
>> Your system is not supposed to recognize gets. If your ruby does not
>> recognize
>> gets, there is something seriously wrong with your ruby installation.
>>
>>
>> HTH,
>> Sebastian

--
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Sebastian Hungerecker

9/30/2007 2:17:00 PM

0

Peter Vanderhaden wrote:
> Sebastian,
> My Ruby installation must be corrupt, as it doesn't recognize gets.
> When I try your solution, I get the following error message:
>
> D:/scripts/ruby/f0.rb:10:in `gets': Bad file descriptor (Errno::EBADF)
> from D:/scripts/ruby/f0.rb:10

Well, he doesn't say that he doesn't recognize gets, he says that an error
occured while executing gets.
It should be noted that Kernel#gets will open ARGV[0] as a file and read that
instead of STDIN when ARGV is not empty, which is the most common cause of
errors with gets. So if that's the problem in your case, try using STDIN.gets
instead of Kernel#gets. If that doesn't help, show the code.


> I'd assume the best way to correct this would be to reinstall Ruby?
> Would you agree?

If your gets is really broken and you're not just using it wrong, then yes.


HTH,
Sebastian
--
Jabber: sepp2k@jabber.org
ICQ: 205544826

Sebastian Hungerecker

9/30/2007 2:20:00 PM

0

Peter Vanderhaden wrote:
> Sebastian,
> FYI, the reason I'm sending the prompt to STDERR instead of STDOUT is
> that I've used reopen to redirect STDOUT to a file. I did that because
> I want to write data to a file. I'm new to this, so if there's a better
> way to write to the file, I'm all ears :)
> PETERV

File.open(filename,'w') do |f|
f.puts "Text that's supposed to go in the file"
puts "Text that's supposed to go to the screen"
f.puts "More text for the file"
STDERR.puts "Error message"
end


HTH,
Sebastian
--
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ICQ: 205544826

7stud 7stud

9/30/2007 2:37:00 PM

0

Peter Vanderhaden wrote:
> Sebastian,
> FYI, the reason I'm sending the prompt to STDERR instead of STDOUT is
> that I've used reopen to redirect STDOUT to a file. I did that because
> I want to write data to a file. I'm new to this, so if there's a better
> way to write to the file, I'm all ears :)
>

How about:

1)
f = File.new("data.txt", "w")
f.write("hello world\n")
f.close()


2)
f = File.open("data.txt", "w") do |file|
file.puts("goodbye mars")
end
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7stud 7stud

9/30/2007 2:40:00 PM

0

7stud -- wrote:
>
> 2)
> f = File.open("data.txt", "w") do |file|
> file.puts("goodbye mars")
> end

Whoops, too slow. And I had some detritus stuck to the front of that
example anyway. It should be:

2)
File.open("data.txt", "w") do |file|
file.puts("goodbye venus")
end
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