Newbie needs help getting user input

Ruby
1

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 = );

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…

2

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.rubyforge.org/

I hope this helps,

~Wayne

3

Peter V. 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 = );

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

4

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.rubyforge.org/

I hope this helps,

~Wayne

5

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

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-forum.com/.

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.

6

Peter V. 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 = );

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

7

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 :slight_smile:
PETERV

Peter V. 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 H. wrote:

Peter V. 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 = );

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

8

Peter V. 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

9

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 H. wrote:

Peter V. 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 = );

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

10

Peter V. 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 :slight_smile:
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

11

Peter V. 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 :slight_smile:

How about:

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

f = File.open(“data.txt”, “w”) do |file|
file.puts(“goodbye mars”)
end

12

7stud,
Thanks! This is obviously much better than what I was doing! Being new
to this type of language, I really appreciate the help! I do have one
more question for you though. What’s the difference between using
file.puts & file.print?

7stud – wrote:

7stud – wrote:

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:

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

13

7stud – wrote:

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:

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

14

Peter V. wrote:

What’s the difference between using file.puts & file.print?

puts adds a newline at the end (if the string doesn’t already end with a
newline).

HTH,
Sebastian