# Using rcov in already running program

**URL:** <https://www.ruby-forum.com/t/using-rcov-in-already-running-program/67472>\
**Category:** Ruby\
**Created:** [September 4, 2006, 2:44pm UTC](https://www.ruby-forum.com/t/using-rcov-in-already-running-program/67472 "2006-09-04T14:44:16Z")\
**Posts on this page:** 9\
**Page:** 1

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**Author:** ![Suraj\_NSKurapati](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/3be4f8/32.png) [@Suraj\_NSKurapati](https://www.ruby-forum.com/u/Suraj_NSKurapati)\
**Post date:** [September 4, 2006, 2:44pm UTC](https://www.ruby-forum.com/t/using-rcov-in-already-running-program/67472/1 "2006-09-04T14:44:16Z")

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Hello,

How can I use rcov from an already running Ruby program?

I’m running a Ruby interpreter that is embedded within a C program.  
This situation is the inverse of how rcov is presently used: rcov is  
used to run \*.rb files instead of ruby.

So, I want to be able to write something like “require  
‘rcov/runner’” and have rcov do it do its thing on the currently  
running Ruby program. This is like running unit tests by simply  
doing “require ‘test/unit’” (which has a Kernel#at\_exit statement  
that runs all the tests before the program terminates).

Thanks for your consideration.  
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**Author:** ![Suraj\_NSKurapati](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/3be4f8/32.png) [@Suraj\_NSKurapati](https://www.ruby-forum.com/u/Suraj_NSKurapati)\
**Post date:** [September 4, 2006, 6:19pm UTC](https://www.ruby-forum.com/t/using-rcov-in-already-running-program/67472/2 "2006-09-04T18:19:50Z")

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On Mon, Sep 04, 2006 at 05:15:24PM +0900, Suraj N. Kurapati wrote:

> doing “require ‘test/unit’” (which has a Kernel#at\_exit statement  
> that runs all the tests before the program terminates).

I’ve never used rcov with an embedded Ruby interpreter, but something  
like  
this should work:

rcov/runner.rb:

require ‘rcov’  
require ‘rbconfig’

# try to load xx, but don’t give up if it’s not available

begin  
require ‘xx’  
rescue LoadError  
end  
begin  
require ‘rcov/report’  
rescue NameError

# hack to make textual reports work in the absence of xx-0.1.0

# Rcov::HTMLCoverage cannot be used without it though

end

rcov\_analyzer = Rcov::CodeCoverageAnalyzer.new  
at\_exit do  
rcov\_analyzer.remove\_hook  
rcov\_analyzer.dump\_coverage\_info([Rcov::TextReport.new])

# use Rcov::HTMLCoverage above to generate HTML reports; the

formatters admit

# a number of options, listed in rcov’s RDoc documentation.

end  
rcov\_analyzer.install\_hook

If you save that as rcov/runner.rb in your $LOAD\_PATH, you will be able  
to

$ cat a.rb

srand(0)  
c = 0  
d = 1  
10.times do |i|  
if rand % (i + 10)  
c += i  
d += 1  
end  
end  
puts “blergh”  
if c \> 4\*d

# stuff

puts “yep”  
else  
puts “nope”

# more stuff

end

puts “Done: #{c+d}”  
$ ruby -I …/head/lib -rrcov/runner a.rb  
blergh  
yep  
Done: 56  
±---------------------------------------------------±------±------±-------+  
| File | Lines | LOC | COV |  
±---------------------------------------------------±------±------±-------+  
|a.rb | 20 | 16 | 81.2% |  
±---------------------------------------------------±------±------±-------+  
|Total | 20 | 16 | 81.2% |  
±---------------------------------------------------±------±------±-------+  
81.2% 1 file(s) 20 Lines 16 LOC

In your case, you can require ‘rcov/runner’ in the embedded interpreter,  
and  
the code loaded/parsed from that moment on will be monitored.  
If you cannot load rcov/runner before the code you want to analyze is  
parsed,  
it might still be possible to make it work by doing  
SCRIPT\_LINES\_\_ = {} unless defined? SCRIPT\_LINES\_\_  
early on. Of course, only the code executed after rcov/runner is loaded  
would  
be analyzed in that case.

rcov/runner.rb seems a good idea and I’d want to add it to the next  
release;  
do you have any suggestions regarding the interface or the default  
options?  
Dumping a textual report like the above one seems to make sense as it is  
akin  
to Test::Unit’s output.

Thanks,

---

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**Author:** ![Suraj\_NSKurapati](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/3be4f8/32.png) [@Suraj\_NSKurapati](https://www.ruby-forum.com/u/Suraj_NSKurapati)\
**Post date:** [September 4, 2006, 8:02pm UTC](https://www.ruby-forum.com/t/using-rcov-in-already-running-program/67472/3 "2006-09-04T20:02:06Z")

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Mauricio F. wrote:

> > doing “require ‘test/unit’” (which has a Kernel#at\_exit statement  
> > that runs all the tests before the program terminates).
> 
> I’ve never used rcov with an embedded Ruby interpreter, but something like  
> this should work:

[code snipped]

This works wonderfully. Thank you!

> In your case, you can require ‘rcov/runner’ in the embedded interpreter, and  
> the code loaded/parsed from that moment on will be monitored.

This is fine for my purpose.

> rcov/runner.rb seems a good idea and I’d want to add it to the next release;  
> do you have any suggestions regarding the interface or the default options?

Yes, I would like a mechanism to pass the regular rcov command-line  
options to the embedded rcov runner. I’m thinking that this can be  
done either by setting the global ARGV array or maybe a RCOV\_ARGV  
array before loading the runner:

RCOV\_ARGV = [’–html’, ‘–no-color’, ‘–save’, ‘coverage.html’]  
require ‘rcov/runner’

> Dumping a textual report like the above one seems to make sense as it is akin  
> to Test::Unit’s output.

This is sufficient, but I would like to see the more detailed HTML  
report as well, so I can know where coverage needs improvement.

Thanks for your consideration.  
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**Author:** ![Suraj\_NSKurapati](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/3be4f8/32.png) [@Suraj\_NSKurapati](https://www.ruby-forum.com/u/Suraj_NSKurapati)\
**Post date:** [September 5, 2006, 2:42am UTC](https://www.ruby-forum.com/t/using-rcov-in-already-running-program/67472/4 "2006-09-05T02:42:42Z")

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Mauricio F. wrote:

> # reports are to be generated. The possible options will be explained in the
> 
> # RDoc documentation.
> 
> Rcov::Runner.generate Rcov::HTMLCoverage, :color =\> false  
> Rcov::Runner.generate Rcov::TextCoverageDiff, :coverage\_diff\_mode =\> :record,  
> :coverage\_diff\_file =\> “coverage.data”

This is good. Please proceed with this approach.

> Passing options with an ARGV feels clunky to me (I never liked that part of  
> RDoc’s API).

Good point. I thought that maybe it would reduce the amount of work  
for you by reusing the existing ARGV handling code. Nevertheless, as  
you’ve shown, it is cleaner to use the Rcov API directly.

> > > Dumping a textual report like the above one seems to make sense as it is akin  
> > > to Test::Unit’s output.  
> > > This is sufficient, but I would like to see the more detailed HTML  
> > > report as well, so I can know where coverage needs improvement.
> 
> I think I’ll either move xx (currently embedded in bin/rcov) to a separate  
> file or rewrite the XHTML generation code using erb (since everybody’s got  
> it). XHTML reports could then be created as shown above.

As long as the interaction with xx is contained within ‘rcov/runner’  
there shouldn’t be any problem from the user’s perspective.

I’m looking forward to the next release. 🙂

Thanks for your support.  
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**Author:** ![Suraj\_NSKurapati](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/3be4f8/32.png) [@Suraj\_NSKurapati](https://www.ruby-forum.com/u/Suraj_NSKurapati)\
**Post date:** [September 5, 2006, 7:02pm UTC](https://www.ruby-forum.com/t/using-rcov-in-already-running-program/67472/5 "2006-09-05T19:02:08Z")

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On Tue, Sep 05, 2006 at 09:39:10AM +0900, Suraj N. Kurapati wrote:

> > # Rcov::Runner.generate formatter [, options] is used to specify which
> > 
> > # reports are to be generated. The possible options will be explained in the
> > 
> > # RDoc documentation.
> > 
> > Rcov::Runner.generate Rcov::HTMLCoverage, :color =\> false  
> > Rcov::Runner.generate Rcov::TextCoverageDiff, :coverage\_diff\_mode =\> :record,  
> > :coverage\_diff\_file =\> “coverage.data”
> 
> This is good. Please proceed with this approach.

Alright then, I’ll document the available report generators  
(“formatters”)  
and their options in the RDoc.

## 

hmmm, which one is better?

lib/cov/runner.rb:

require ‘rcov/runner’

ruby -rcov/runner myscript.rb

or

lib/cov.rb -\> ruby -rcov myscript.rb

Naming your lib r.\* can be handy at times…

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**Author:** ![Suraj\_NSKurapati](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/3be4f8/32.png) [@Suraj\_NSKurapati](https://www.ruby-forum.com/u/Suraj_NSKurapati)\
**Post date:** [September 4, 2006, 11:58pm UTC](https://www.ruby-forum.com/t/using-rcov-in-already-running-program/67472/6 "2006-09-04T23:58:30Z")

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On Tue, Sep 05, 2006 at 03:00:07AM +0900, Suraj N. Kurapati wrote:

> Mauricio F. wrote:
> 
> > On Mon, Sep 04, 2006 at 05:15:24PM +0900, Suraj N. Kurapati wrote:  
> > I’ve never used rcov with an embedded Ruby interpreter, but something like  
> > this should work:
> 
> [code snipped]

[…]

> require ‘rcov/runner’  
> What about something like this?

require ‘rcov/runner’

# if nothing else is done, it generates a plain text report, no HTML

# Rcov::Runner.generate formatter [, options] is used to specify which

# reports are to be generated. The possible options will be explained in

the

# RDoc documentation.

Rcov::Runner.generate Rcov::HTMLCoverage, :color =\> false  
Rcov::Runner.generate Rcov::TextCoverageDiff, :coverage\_diff\_mode =\>  
:record,  
:coverage\_diff\_file =\> “coverage.data”

Passing options with an ARGV feels clunky to me (I never liked that part  
of  
RDoc’s API).

> > Dumping a textual report like the above one seems to make sense as it is akin  
> > to Test::Unit’s output.
> 
> This is sufficient, but I would like to see the more detailed HTML  
> report as well, so I can know where coverage needs improvement.

I think I’ll either move xx (currently embedded in bin/rcov) to a  
separate  
file or rewrite the XHTML generation code using erb (since everybody’s  
got  
it). XHTML reports could then be created as shown above.

---

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**Author:** ![Suraj\_NSKurapati](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/3be4f8/32.png) [@Suraj\_NSKurapati](https://www.ruby-forum.com/u/Suraj_NSKurapati)\
**Post date:** [September 8, 2006, 7:08pm UTC](https://www.ruby-forum.com/t/using-rcov-in-already-running-program/67472/7 "2006-09-08T19:08:41Z")

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Mauricio F. wrote:

> rescue NameError  
> end  
> rcov\_analyzer.install\_hook

I can’t find Rcov::CodeCoverageAnalyzer#dump\_coverage\_info,  
Rcov::HTMLCoverage, or Rcov::TextReport in the RDoc shipped with  
rcov 0.7.0.1

Aren’t these internal structures undocumented because they shouldn’t  
be used by outsiders?

Thanks for your attention.  
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**Author:** ![Suraj\_NSKurapati](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/3be4f8/32.png) [@Suraj\_NSKurapati](https://www.ruby-forum.com/u/Suraj_NSKurapati)\
**Post date:** [September 5, 2006, 8:42pm UTC](https://www.ruby-forum.com/t/using-rcov-in-already-running-program/67472/8 "2006-09-05T20:42:19Z")

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Mauricio F. wrote:

> hmmm, which one is better?
> 
> require ‘rcov/runner’
> 
> ruby -rcov/runner myscript.rb

This would agree more with RubyGems convention.

> or
> 
> lib/cov.rb -\> ruby -rcov myscript.rb
> 
> Naming your lib r.\* can be handy at times…

That is pretty neat, but it might be misleading when written in  
source code: require ‘cov’ … “cov? is that rcov or something else?”

You could make both versions available by having lib/cov.rb load  
lib/rcov/runner.rb.

Nevertheless, the choice is yours. 🙂  
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**Author:** ![Suraj\_NSKurapati](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/3be4f8/32.png) [@Suraj\_NSKurapati](https://www.ruby-forum.com/u/Suraj_NSKurapati)\
**Post date:** [September 10, 2006, 10:24am UTC](https://www.ruby-forum.com/t/using-rcov-in-already-running-program/67472/9 "2006-09-10T10:24:22Z")

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On Sat, Sep 09, 2006 at 01:54:19AM +0900, Suraj N. Kurapati wrote:

> I can’t find Rcov::CodeCoverageAnalyzer#dump\_coverage\_info,  
> Rcov::HTMLCoverage, or Rcov::TextReport in the RDoc shipped with  
> rcov 0.7.0.1
> 
> Aren’t these internal structures undocumented because they shouldn’t  
> be used by outsiders?

Yes, I originally didn’t want them to be used externally because I  
didn’t want  
to commit to keeping API compatibility, etc. But you’ve presented a good  
use  
case that warrants exposing some of them, so I’ll think about the API to  
make  
sure it is reasonable and will not require changes in short, and  
document it.