How to run one script from another, and capture the output

Ruby
1

I have the following hypothetical script that requires arguments to run.
The command line execution looks like this:

‘ruby distance_traveled.rb 60 2.5’

The output would be the following:

‘You have traveled a distance of 150 miles.’

How would I run the above execution from inside another script, and
capture the output above (the 150 miles portion at least)?

Thanks in advance!

2

On Dec 29, 2009, at 7:11 PM, John S. wrote:

How would I run the above execution from inside another script, and
capture the output above (the 150 miles portion at least)?

Thanks in advance!

Posted via http://www.ruby-forum.com/.

I’ve faced an exactly same problem when was testing command line
utilities, by capturing an output and comparing it with expected one.
Here is a gem for it:

http://github.com/fkocherga/cmd_line_test

You may look on running and capturing code there.

3

On Dec 29, 2009, at 8:11 PM, John S. wrote:

How would I run the above execution from inside another script, and
capture the output above (the 150 miles portion at least)?

output = ruby distance_traveled.rb 60 2.5

The backticks cause the standard output of the command to be captured
and stored in a Ruby string.

Gary W.

4

Gary W. wrote:

On Dec 29, 2009, at 8:11 PM, John S. wrote:

How would I run the above execution from inside another script, and
capture the output above (the 150 miles portion at least)?

output = ruby distance_traveled.rb 60 2.5

The backticks cause the standard output of the command to be captured
and stored in a Ruby string.

Gary W.

Thanks so much for that!

One more quick question. If distance_traveled.rb sits in a different
directory than the current script that’s calling it, how would I specify
it? For example, say it is in ~project/lib/distance_traveled.rb

Thanks again!

5

On 30.12.2009 14:06, John S. wrote:

One more quick question. If distance_traveled.rb sits in a different
directory than the current script that’s calling it, how would I specify
it? For example, say it is in ~project/lib/distance_traveled.rb

output = ruby ~project/lib/distance_traveled.rb 60 2.5 :stuck_out_tongue:

Or perform string interpolation, if you don’t want to hardcode anything:
path = “~/project/lib/”
script = “script.rb”
args = “my args”

output = #{path}#{script} #{args}

6

On Dec 30, 2009, at 8:06 AM, John S. wrote:

One more quick question. If distance_traveled.rb sits in a different
directory than the current script that’s calling it, how would I specify
it? For example, say it is in ~project/lib/distance_traveled.rb

The command is parsed by the shell so ~project/lib/distance_traveled.rb
should work or a relative or absolute path of course.

Gary W.

7

Gary W. wrote:

On Dec 30, 2009, at 8:06 AM, John S. wrote:

One more quick question. If distance_traveled.rb sits in a different
directory than the current script that’s calling it, how would I specify
it? For example, say it is in ~project/lib/distance_traveled.rb

The command is parsed by the shell so ~project/lib/distance_traveled.rb
should work or a relative or absolute path of course.

Gary W.

Thanks for the help!

However, I should also add that in the above example,
distance_traveled.rb requires other .rb files sitting in the same lib
directory.

I have no problem running distance_traveled.rb from inside lib. However,
from another directory, when I try to run the program using relative
path (ie. ‘ruby …/…/lib/distance_traveled.rb’), I get
"distance_traveled.rb:1:in `require’: no such file to load – ", in
reference to the other .rb file(s) in the lib directory.

Any suggestions for this issue? Thanks again!

8

On Dec 30, 2009, at 12:24 PM, John S. wrote:

Any suggestions for this issue? Thanks again!

If the files aren’t in standard library locations, you’ll want to make
sure that you name them relative to the source file using something
like:

require File.join(File.expand_path(File.dirname(FILE)), ‘otherfile’)

This ensures that the require method sees a fully qualified path to
‘otherfile’ where ‘otherfile’ is found relative to the directory
containing the source file instead of relative to the current working
directory of the process.

Gary W.