Help with Ruby & PrinceXML

Question

I'm trying to write a very simple markdown-like converter in ruby, then pass the output to PrinceXML (which is awesome). Prince basically converts html to pdf.

Here's my code:

#!/usr/bin/ruby
# USAGE: command source-file.txt target-file.pdf

# read argument 1 as input
text = File.read(ARGV[0])

# wrap paragraphs in paragraph tags
text = text.gsub(/^(.+)/, '<p>\1</p>')

# create a new temp file for processing
htmlFile = File.new('/tmp/sample.html', "w+")

# place the transformed text in the new file
htmlFile.puts text

# run prince
system 'prince /tmp/sample.html #{ARGV[1]}'

But this dumps an empty file to /tmp/sample.html. When I exclude calling prince, the conversion happens just fine.

What am I doing wrong?

the Tin Man · Accepted Answer · 2011-06-04T05:39:59.813

1

It's possible that the file output is being buffered, and not written to disk, because of how you are creating the output file. Try this instead:

# create a new temp file for processing
File.open('/tmp/sample.html', "w+") do |htmlFile|

  # place the transformed text in the new file
  htmlFile.puts text

end

# run prince
system 'prince /tmp/sample.html #{ARGV[1]}'

This is idiomatic Ruby; We pass a block to File.new and it will automatically be closed when the block exits. As a by-product of closing the file, any buffered output will be flushed to disk, where your code in your system call can find it.

edited Jun 04 '11 at 05:39

answered Jun 04 '11 at 04:10

the Tin Man

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I get the following warning: `File::new() does not take block; use File::open() instead` – Jun 04 '11 at 05:38
Yes, that'd be correct. I'll tweak the answer to reflect reality. – the Tin Man Jun 04 '11 at 05:39
I'm starting to think that there are two bugs at once here: buffered output and trying to do string interpolation inside single quotes. – mu is too short Jun 04 '11 at 05:46

mu is too short · Answer 2 · 2011-06-04T06:28:03.587

0

From the fine manual:

prince doc.html -o out.pdf
Convert doc.html to out.pdf.

I think your system call should look like this:

system "prince /tmp/sample.html -o #{ARGV[1]}"

Also note the switch to double quotes so that #{} interpolation will work. Without the double quotes, the shell will see this command:

prince /tmp/sample.html #{ARGV[1]}

and then it will ignore everything after # as a comment. I'm not sure why you end up with an empty /tmp/sample.html, I'd expect a PDF in /tmp/sample.pdf based on my reading of the documentation.

edited Jun 04 '11 at 06:28

answered Jun 04 '11 at 03:06

mu is too short

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Hmmm... I've been using Prince for years and I've never once used the `-o` flag. It seems to have no effect. And, yes, the big problem is that with the `system` call the script creates an empty file, but without it the script processes the file as expected. – Jun 04 '11 at 05:39
@Oliver: Does using double quotes on your `system` call make a difference? And what if you flush or close `htmlFile` before `system` as Tin Man suggests? – mu is too short Jun 04 '11 at 05:44
I changed it to doubles, and no, it didn't make a difference. And, yes, what @theTinMan suggested worked perfectly. – Jun 04 '11 at 05:48
@Oliver: But does it pay attention to `ARGV[1]` without the double quotes or does it just produce `/tmp/sample.pdf`? – mu is too short Jun 04 '11 at 06:27

Help with Ruby & PrinceXML

2 Answers2