Sunday, 19 January 2014

Combining multiple PDF documents into one

A number of times I have faced the requirement of combining multiple PDF files into a single file. Doing that is fairly simple actually. It can be done using a number of tools. Two ways of doing it using tools very common on linux systems are as follows.
A lot many systems have imagemagick installed.  Using it is so simple that I use it as my default tool for this purpose.

convert file1.pdf /path/to/file2.pdf /destination/path/store.pdf

It takes a lot of options. For PDFs containing images, it is better to specify a quality parameter.

convert -quality 100 mine1.pdf mine2.pdf merged.pdf
Ghostscript is also very commonly found package in linux systems. Its usage is a little more obscure. However, it is very fast. I use it when I need to get PDF files of reduced size.

gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/screen -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input1.pdf input2.pdf

The above however reduces image quality badly. To get decent image quality with a little larger PDFs, we can use the following.

gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input1.pdf input2.pdf

gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -dPDFSETTINGS=/prepress -sOutputFile=output.pdf input1.pdf input2.pdf

Tuesday, 7 January 2014

Disable compression in Net::HTTP

Recently while upgrading to Ruby 2, I found a JSON API call was failing intermittently. The code was failing when I was trying to parse the response using JSON.parse. Investigating further, I found that the call was successful; but for some calls the response was different than the response for others. Looking at the response, I found it was not JSON at all. It looked like the following.


I had no clue as to what to make out of such a response. Reading up on it, I found out that the above might be a compressed response. It appeared that the server had the liberty of choosing whether to compress the response or not and whenever the response was uncompressed, my code was working fine. Looking into improvements introduced in Ruby 2, I found that Net::HTTP now automatically requests gzip and deflate compression by default. All I needed to do was to stop doing that and ask for uncompressed response. As my response was rather small, it would hardly matter. To request uncompressed response, I just needed to add the following header to my requests.

'Accept-Encoding' => 'identity'

Sunday, 5 January 2014

Counting words on the command line

Recently, I have been writing a number of essays with various word limits. So, I have been finding myself in need of doing frequent word counts. Getting a word count for a file is easy using the wc utility.

wc -w /path/to/file

However, sometimes I just write a piece in a browser text box, which don't have word count. So, I want to get a word count from the console rather than saving it to a file and working with it. It turned out to be quite easy actually. I just had to cat the entire text and pipe that to wc.

cat << EOF | wc -w
>Your text here
>More here.