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How to Export TWiki Data in CSV Format for Use in Excel

2011-11-11 - 21:19:10 by PeterThoeny in Development
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Sometimes it is desirable to export TWiki forms based data from TWiki applications. CSV (comma-separated_values) is a simple file format that is widely supported by many applications, including spreadsheet programs such as Excel. This blog introduces the CSV format and explains how to generate a CSV file on the fly in a TWiki application.

The CSV format is not clearly defined, there is no real CSV standard. In common usage almost any delimiter-separated text data may be referred to as a CSV file. Traditionally, however, lines in the text file represent rows in a table, and commas separate the columns. This traditional understanding is defined in RFC 4180, which is the best known effort to formalize a CSV standard.

In its most basic form, each record is a line, and fields are separated by a comma. Here is an example that contains a header row representing the field names, and two records:

First name,Last name,Age

Fields may contain commas, double-quotes, and line breaks (CRLF); in which case they should be enclosed in double-quotes. If double-quotes are used to enclose fields, then a double-quote appearing inside a field must be escaped by preceding it with another double-quote. Example:

Field A,Field B,Field C,Field D
normal field,"field, with, commas","field with
line feed","field with ""quoted"" text"

Now that we understand the basics of CSV, let's see how we can generate a CSV file from TWiki content. As long as content is structured using TWiki forms it is easy to generate reports on the fly using a SEARCH variable. The search can be formatted to produce output in CSV format.

Let's look at the ContactDbAddOn, which is a contact database. Each record is a TWiki page that has a ContactForm with fields Salutation, Name, Job Title, Company, Phone, Mobile, Fax, Email, and URL.

Here is a search that shows all records using the default search format:

 "form.name = 'ContactForm'"

Now let's add a search format to generate the CSV output. We add a header line containing the names of the fields (the format parameter should be on one line) :

 "form.name = 'ContactForm'"
 header="Salutation,Name,Job Title,Company,Phone,Mobile,Fax,Email,URL"
 format="$quot$formfield(Salutation)$quot,$quot$formfield(Name)$quot,$quot$formfield(Job Title)$quot,$quot$formfield(Company)$quot,

export-csv-600.png This search already produces the proper CSV output with fields enclosed in double-quotes. There are some limitations though:

  1. Double quotes in fields are not escaped - they should be escaped.
  2. WikiWords in form fields are automagically expanded into links - they should be escaped.
  3. Even if a page only contains the SEARCH, the TWiki skin adds headers with pulldown menus and footers - all output except the SEARCH should be suppressed.
  4. Content is delivered as HTML, e.g. shown in the browser - the user expects to see a "save file" dialog box.

1. Double quotes in fields are not escaped: TWiki currently has no easy way to escape a double-quote into two double-quotes, so this is a limitation we have to live with.

2. WikiWords in form fields are expanded into links: We can prevent that by enclosing the SEARCH in <noautolink> tags:


3. Even if a page only contains just the SEARCH, the TWiki skin adds headers with pulldown menus and footers: We can suppress all output except the SEARCH by specifying the text skin and a content type of plain text. Assuming we have a ContactsAsCSV page in the Sandbox web that contains just the <noautolink> tag and the SEARCH, we get the plain text result by adding these URL parameters to the page URL:


4. Content is delivered as HTML, e.g. shown in the browser: The user expects to see a "save file" dialog box. We change the content type from plain text to text/csv, and set the content-disposition to attachment; filename=Contacts.csv as defined in RFC 1806 to suggest the file name Contacts.csv in the save-as dialog box. Here is a link that points to the ContactsAsCSV page with proper parameters (the link should be all on one line) :

<a href="http://example.com/do/view/Sandbox/ContactsAsCSV?skin=text;
contenttype=text/csv%0Acontent-disposition%3A+attachment%3B+filename%3DContacts.csv" target="_top">Export to CSV file</a>

That's basically it. We can further improve this, such as generating a suggested file name with current date. You are invited to download and install the ContactDbAddOn, it has a working export to CSV feature.




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Topic revision: r2 - 2011-11-14 - PeterThoeny

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