File handling demonstration

Input and Output in Ruby example from a Well House Consultants training course
More on Input and Output in Ruby [link]

Source code: filestuff.rb Module: R106

# Open files for read, overwrite and append

fhi = File.new "canal_ip.txt"
filtered = File.new "selected.txt","w"
logged = File.new "logged.txt","a"
counter = 0

# Process a file of data line by line

fhi.readlines.each do |host|
        counter += 1
        # all lines reported to the runner
        STDOUT.write host
        if counter < 10
                # 10 lines written to selected.txt
                filtered.write host
        end
end

# Close files that we have finished reading / writing

fhi.close
filtered.close

# Write and close out logs

# Count of work done logged to control / error channel
STDERR.write "Total of #{counter} lines of data processed\n"
# Collect current date / time object
# and write it to log file in default format
present = Time::now
logged.write "Program run #{present}\n"
logged.close

Learn about this subject

This module and example are covered on the following public courses:
* Learning to program in Ruby
* Ruby Programming
Also available on on site courses for larger groups

Books covering this topic

Yes. We have over 700 books in our library. Books covering Ruby are listed here and when you've selected a relevant book we'll link you on to Amazon to order.

Other Examples

This example comes from our "Input and Output in Ruby" training module. You'll find a description of the topic and some other closely related examples on the "Input and Output in Ruby" module index page.

Full description of the source code

You can learn more about this example on the training courses listed on this page, on which you'll be given a full set of training notes.

Many other training modules are available for download (for limited use) from our download centre under an Open Training Notes License.

Other resources

• Our Solutions centre provides a number of longer technical articles.
• Our Opentalk forum archive provides a question and answer centre.
• The Horse's mouth provides a daily tip or thought.
• Further resources are available via the resources centre.
• All of these resources can be searched through through our search engine
• And there's a global index here.

Purpose of this website

This is a sample program, class demonstration or answer from a training course. It's main purpose is to provide an after-course service to customers who have attended our public private or on site courses, but the examples are made generally available under conditions described below.

Web site author

This web site is written and maintained by Well House Consultants.

Conditions of use

Past attendees on our training courses are welcome to use individual examples in the course of their programming, but must check the examples they use to ensure that they are suitable for their job. Remember that some of our examples show you how not to do things - check in your notes. Well House Consultants take no responsibility for the suitability of these example programs to customer's needs.

This program is copyright Well House Consultants Ltd. You are forbidden from using it for running your own training courses without our prior written permission. See our page on courseware provision for more details.

Any of our images within this code may NOT be reused on a public URL without our prior permission. For Bona Fide personal use, we will often grant you permission provided that you provide a link back. Commercial use on a website will incur a license fee for each image used - details on request.