# How to abruptly end a program? **URL:** \ **Category:** Ruby\ **Created:** [March 15, 2008, 7:01am UTC](https://www.ruby-forum.com/t/how-to-abruptly-end-a-program/132010 "2008-03-15T07:01:50Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![tbcox23](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/b9bd4f/32.png) [@tbcox23](https://www.ruby-forum.com/u/tbcox23)\ **Post date:** [March 15, 2008, 7:01am UTC](https://www.ruby-forum.com/t/how-to-abruptly-end-a-program/132010/1 "2008-03-15T07:01:50Z")
I read in \ (p. 303) - "“If Ruby comes across a line anywhere in the source containing just “\_ _END_ \_”, with no leading or trailing whitespace, it treats that line as the end of the program—any subsequent lines will not be treated as program code.” That’s not what’s happening for me. The following - \_ _END_ \_ **END** _END_ all produce the same result for me - “undefined local variable or method” That DOES bring the program to an abrupt end, but its rather ungraceful. Is this the intended result - a crash due to an interpreter error? Tom – ```auto Tom C., MS MA, LMHC Private practice Psychotherapist Bellingham, Washington, U.S.A: (360) 920-1226 << removed_email_address@domain.invalid >> (email) << TomCloyd.com >> (website & psychotherapy weblog) << sleightmind.wordpress.com >> (mental health issues weblog) << directpathdesign.com >> (web site design & consultation) ``` ---
**Author:** ![tbcox23](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/b9bd4f/32.png) [@tbcox23](https://www.ruby-forum.com/u/tbcox23)\ **Post date:** [March 15, 2008, 7:12am UTC](https://www.ruby-forum.com/t/how-to-abruptly-end-a-program/132010/2 "2008-03-15T07:12:23Z")
Hi, On Sat, Mar 15, 2008 at 5:01 PM, Tom C. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > all produce the same result for me - “undefined local variable or method” > That DOES bring the program to an abrupt end, but its rather ungraceful. > Is this the intended result - a crash due to an interpreter error? Certainly not 🙂 Though I guess any identifier could do that then. Are you sure there’s no whitespace or other content on the line? Can you show us an example? celtic@sohma:~$ cat test.rb #!/usr/bin/env ruby puts “Hi there!” **END** This is just great. celtic@sohma:~$ ruby test.rb Hi there! celtic@sohma:~$ Thanks! Arlen ---
**Author:** ![tbcox23](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/b9bd4f/32.png) [@tbcox23](https://www.ruby-forum.com/u/tbcox23)\ **Post date:** [March 15, 2008, 7:14am UTC](https://www.ruby-forum.com/t/how-to-abruptly-end-a-program/132010/3 "2008-03-15T07:14:10Z")
Tom C. wrote: > all produce the same result for me - “undefined local variable or method” > That DOES bring the program to an abrupt end, but its rather ungraceful. > Is this the intended result - a crash due to an interpreter error? What the quote (a bit ambiguous perhaps) means is that the **END** line and following lines are not treated as part of the program text. It has nothing to do with control flow. It’s like comment block that runs to the end of the file without any explicit termination. (It’s more than that because you can read it with DATA.) ---
**Author:** ![tbcox23](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/b9bd4f/32.png) [@tbcox23](https://www.ruby-forum.com/u/tbcox23)\ **Post date:** [March 15, 2008, 7:54am UTC](https://www.ruby-forum.com/t/how-to-abruptly-end-a-program/132010/4 "2008-03-15T07:54:38Z")
Tom C. wrote: > > > **END** > > > It has nothing to do with control flow. It’s like comment block that > > > runs to the end of the file without any explicit termination. (It’s > > > more than that because you can read it with DATA.) > > OK, but couldn’t ANY uninitialized variable achieve the same messy > result? What’s the point? This surely can’t be the intended result. > Makes no sense to me. **END** by itself on a line shouldn’t exit the program. If you’re getting that error, maybe there is an extra char on the line. A space perhaps? ---
**Author:** ![tbcox23](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/b9bd4f/32.png) [@tbcox23](https://www.ruby-forum.com/u/tbcox23)\ **Post date:** [March 15, 2008, 7:48am UTC](https://www.ruby-forum.com/t/how-to-abruptly-end-a-program/132010/5 "2008-03-15T07:48:10Z")
Joel VanderWerf wrote: > > _END_ > > runs to the end of the file without any explicit termination. (It’s > > more than that because you can read it with DATA.) OK, but couldn’t ANY uninitialized variable achieve the same messy result? What’s the point? This surely can’t be the intended result. Makes no sense to me. t. – ```auto Tom C., MS MA, LMHC Private practice Psychotherapist Bellingham, Washington, U.S.A: (360) 920-1226 << removed_email_address@domain.invalid >> (email) << TomCloyd.com >> (website & psychotherapy weblog) << sleightmind.wordpress.com >> (mental health issues weblog) << directpathdesign.com >> (web site design & consultation) ``` ---
**Author:** ![tbcox23](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/b9bd4f/32.png) [@tbcox23](https://www.ruby-forum.com/u/tbcox23)\ **Post date:** [March 15, 2008, 8:38am UTC](https://www.ruby-forum.com/t/how-to-abruptly-end-a-program/132010/6 "2008-03-15T08:38:35Z")
Tom C. wrote: > result: > test under way > input var: > 5 > 5 > > Here, we don’t get an error. We just get ignored. > This is nuts. Looks correct. The **END** line and everything after it is ignored. What’s your example with an error? ---
**Author:** ![tbcox23](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/b9bd4f/32.png) [@tbcox23](https://www.ruby-forum.com/u/tbcox23)\ **Post date:** [March 15, 2008, 8:19am UTC](https://www.ruby-forum.com/t/how-to-abruptly-end-a-program/132010/7 "2008-03-15T08:19:51Z")
Joel VanderWerf wrote: > > > > \_ _END_ \_ > > > > line and following lines are not treated as part of the program > > > > perhaps? Yes, that would explain it, but I made sure this problem didn’t occur from the beginning, which is one reason I’m puzzled. I really don’t see anything wrong with what I’m feeding the interpreter. So, I did a different test program - require ‘readline’ puts "test under way\ninput var: " #opt = readline( “=–\> \n”) opt = gets.chomp puts( opt) **END** puts( opt) result: test under way input var: 5 5 Here, we don’t get an error. We just get ignored. This is nuts. t. – ```auto Tom C., MS MA, LMHC Private practice Psychotherapist Bellingham, Washington, U.S.A: (360) 920-1226 << removed_email_address@domain.invalid >> (email) << TomCloyd.com >> (website & psychotherapy weblog) << sleightmind.wordpress.com >> (mental health issues weblog) << directpathdesign.com >> (web site design & consultation) ``` ---
**Author:** ![tbcox23](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/b9bd4f/32.png) [@tbcox23](https://www.ruby-forum.com/u/tbcox23)\ **Post date:** [March 15, 2008, 8:42am UTC](https://www.ruby-forum.com/t/how-to-abruptly-end-a-program/132010/8 "2008-03-15T08:42:41Z")
On Saturday 15 March 2008, Tom C. wrote: > > > > > That’s not what’s happening for me. The following - > > > > > What the quote (a bit ambiguous perhaps) means is that the **END** > > > > > getting that error, maybe there is an extra char on the line. A space > > > > > #opt = readline( “=–\> \n”) > > Here, we don’t get an error. We just get ignored. > This is nuts. > > t. As others said, when ruby sees the **END** identifier on a line by itself (without leading or trailing spaces), it treats it, and any text following it, approximately as a comment. This means that the code is not parsed (syntax errors after that line aren’t recognized) and, obviously, not executed. Besides, the constant DATA is set to a File object which contains that text. This is consistent with the result you get from your piece of code: without the **END** , 5 would have been written 3 times: the first when you entered it from the keyboard, the other two because of the two puts. Since the second puts is after **END** , instead, you only get it twice: the second puts is ignored. Try this, for example: puts “This is the class of DATA: #{DATA.class}” puts “These are the contents of DATA:\n\n#{DATA.read}” **END** This is not valid ruby code The output is: This is the class of DATA: File These are the contents of DATA: This is not valid ruby code Of course, removing the **END** line causes a syntax error: ./prova.rb:6: syntax error, unexpected kNOT, expecting $end This is not valid ruby code Regarding your first piece of code (the one which produces the NoMethodError), are you sure the error isn’t produced before end? Stefano ---
**Author:** ![tbcox23](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/b9bd4f/32.png) [@tbcox23](https://www.ruby-forum.com/u/tbcox23)\ **Post date:** [March 15, 2008, 8:56am UTC](https://www.ruby-forum.com/t/how-to-abruptly-end-a-program/132010/9 "2008-03-15T08:56:09Z")
Stefano C. wrote: > > > > > > I read in \ (p. 303) - ""If Ruby comes > > > > > > all produce the same result for me - "undefined local variable or > > > > anything wrong with what I’m feeding the interpreter. > > puts is after **END** , instead, you only get it twice: the second puts is > This is the class of DATA: File > are you sure the error isn’t produced before end? > > Stefano Stefano, You’re right. I misread my own output - seeing two 5’s, I thought them to be output, without realizing that the first wasn’t. Yes, it’s getting a bit late here. Maybe it’s time to stop. Thanks to you and Joel for your comments! t. – ```auto Tom C., MS MA, LMHC Private practice Psychotherapist Bellingham, Washington, U.S.A: (360) 920-1226 << removed_email_address@domain.invalid >> (email) << TomCloyd.com >> (website & psychotherapy weblog) << sleightmind.wordpress.com >> (mental health issues weblog) << directpathdesign.com >> (web site design & consultation) ```