I have been reading Linux Shell Scripting Cookbook by Sarath Lakshman, published by Packt, for a while. While most people I know learn shell scripts themselves, I was looking to refresh my concepts a little as well as have a reference lying around on the table for fast access. Since I was asked to review it for someone else, I thought I might as well post the review here.

First of all, let me remark by saying that shell scripting is something learned more on a need basis than as a tool to solve the main problem. People would seldom write shell scripts as standalone programs (exceptions exist). However, what makes shell scripting invaluable to know is the fact that knowing some tricks can save several minutes, or hours, of work by automating and simplifying certain tasks, generally (but not restricted to) file management and data processing. Linux Shell Scripting Cookbook does go quite far in pursuing this goal, and is appropriate for both beginners who are looking to gain dexterity in shell scripting, as well as intermediate users who wish to polish their skills. The book also can double up as a quick reference, though I would argue that the "Advanced Bash Scripting Guide" would suit that more.

At the outset, the author clarifies that the focus will be on Bash. This, people may or may not like, but the fact that bash has become ubiquitous in terms of the available shells on Unix-like systems today, starting out with bash is not a bad thing to do. Besides, learning other shell scripting languages while knowing bash isn't too hard, since the paradigm remains the same.

Let's go through the books from the aspects I found most relevant.

Organization

The book is organized into chapters based more on utility than scripting concepts themselves, although the language aspects are brought onto the reader gradually. For instance, the examples in the first chapter focus more on the basic data elements (variables, arrays, functions etc.) as well as operators (for numbers, files etc.), and all the examples demonstrate simple usage of these concepts, and he further chapters build upon these in a gradual manner.

At the same time, if the reader has some familiarity with shell scripting and needs to only refresh or learn a certain concept, he/she needs to just read the relevant chapter. It is not too difficult to grasp the examples of the later chapters, provided some basic shell knowledge is assumed.

Content and Presentation

A positive trait in the presentation of this book is that it is all based on practical everyday examples which, with minor adaptation, can be used by many for their own daily tasks. For instance, there are several examples which describe searching for and processing files, which, I'd imagine, many users would want to do on a regular basis. Thus, providing realistic examples allows the book to double its utility. The language and approach used is simple and conversational, and the presentation is very clear, with each idea being described as a problem statement followed by a "How to do it" section with the actual code, and ending with a discussion of the nitty-gritties of the code. It is easy to go for a quick scan for those in a hurry, while those who with to read in more detail will not be disappointed either.

The book also covers a wide array of applications. For instance, there are examples on automating fetching web pages and processing them, demonstrations of parsing and simplifying and even some queries around databases wrapped around in shell. It also spans to utilities and tasks connected to statistics, backups, compression, version control and many more.

Breadth and Depth

The book goes into a fair amount of detail in terms of describing the shell scripting concept under consideration. The examples used go into a fair amount of detail in order to describe to the user all the aspects involved in the method or command being used. The concepts described are fairly complete, and would be sufficient for the reader to use immediately or with just a little bit of fine tuning. In terms of breadth, the book covers most of the features of shell scripting while also describing the various facilities the shell provides access to in a Unix-like environment. Thus, the book does not disappoint in this front either.

In summary...

In summary, probably the only thing I'd have liked to see more of is some emphasis on how to write more efficient shell scripts. Granted, most of the shell scripts described in the book are very simple and succinct, but a some words on how loops can be made better, or how to spot situations where pipes are not needed to solve a problem etc. might have been a nice addition. Some explanation of differences with dash, tcsh, zsh etc. might also have been nice, since a lot of users have different default shells. But all this isn't going to prevent me from giving this book a high rating, since it delivers quite well on the promises it makes at the beginning.

This is definitely a good book to have near your desk, and kudos to the author for having taken the effort to put it together. I would highly recommend it to the beginner and occasional shell user for a thorough read, and to an intermediate to have on his/her desk for borrowing the cool scripting ideas and applications the author has written in this book.

Over the next month or so, I've decided to read an interesting book which covers one of my favourite topics, shell scripting. The book is Linux Shell Scripting Cookbook. It has been quite a while since I have actually read a book on a programming topic (other than K&R or the like), but I guess it does feel "complete" to gain knowledge from a book and feel as though we have gained at least some mastery over the topic!

Updates on this will follow.

As a follow up to my previous post on the same topic, now DuckDuckGo supports what I wanted:

• !dpkg %s goes to http://packages.debian.org/%s
• !dpts %s goes to http://packages.qa.debian.org/%s
• !dbugs %s goes to http://bugs.debian.org/%s

Someone rightly pointed out in my last post that anyone can have these customizations in any good browser. That is correct, but often, I use a browser in a machine where my custom quick-searches are not available, but a quick access to my search engine is. In such situations, I find this useful. I thought some others might like it too. :-)

So, DuckDuckgo now has !bang search goodness for Debian packages (!dpackages) and Debian BTS (!dbugs). The BTS search actually launches the "search", while I'd have preferred just http://bugs.debian.org/%s, so that !dbugs src:python-numpy would just take me directly to the numpy bug page, but it's a start. The search engine creator is very receptive to comments, though, and I am sure you can reason with him if you feel most people would find it useful if it is changed to something else; I wasn't sure what the best course of action was, so I haven't talked to him yet.

Here is the full list of !bang searches in DuckDuckGo, and a submission form to request for new ones. Enjoy!

Even in the modern times of AJAX, Web 2+ and what not, Elinks is one of my favourite browsers, at least for browsing some sites. The reasons are simple: it cuts the unnecessary distractions, and allows you to digest text based information rather quickly. In addition, since it doesn't display any images or flashy elements like Flash, pages load lightning fast even on poor connections, making it an excellent option.

Unfortunately, some sites don't really work very well with Elinks, and for those, I do one of two things. For the ones which are really complex, such as secure login sites with too much AJAX, I just resort to one of the "standard" graphical browsers. For some others, I try to work around the problem using Elinks' rich scripting interface available in many programming languages including Perl and Ruby. I chose Lua, since it seemed simple enough to learn. I wanted to share with you some of the simple workarounds I implemented for some sites I visit often.

The first quirk is with the Debian BTS, whose CSS isn't properly interpreted by Elinks (see 593804 and 593840 for details). The short story: the BTS renders like this:

So, I grabbed the CSS, and made some small changes (described in the above mentioned bug reports), and got a new CSS file. I put it in /home/kumar/Kumar/bugs.css, and added the following to my ~/.elinks/hooks.lua:

-- Use an alternate CSS for the Debian BTS to work around some quirks
function debian_bts_format_html_hook (html)
   return string.gsub(html, "/css/bugs.css", 'file:///home/kumar/Kumar/bugs.css')
end

function pre_format_html_hook (url, html)
   if sstrfind (url, "bugs.debian.org") then
      return blonnet_format_html_hook(html)
   end
   return nil
end

and with it, the BTS renders like this:

Much more readable!

The second simple example, for which I won't include images, is the Mobile Twitter interface. The mobile Twitter interface is very convenient and functional in Elinks; however, by default, the text font seems to be a light grey, which is not discernible in the bright background. A default user.css file would be a possible solution, but I have not decided whether to go for it just yet. So, for the Twitter site, I add a function like this:

-- Make the status messages black on Mobile Twitter
function mobile_twitter_format_hook(html)
   return string.gsub(html, ".status.-}", '.status {word-wrap: break-word; color : #000;}')
end

And alter the actual hook function to:

function pre_format_html_hook (url, html)
   if sstrfind (url, "bugs.debian.org") then
      return debian_bts_format_html_hook(html)
   elseif sstrfind (url, "mobile.twitter.com") then
      return mobile_twitter_format_hook(html)
   end
   return nil
end

Finally, a more complicated example. I like reading the Indian business newspaper the Hindu Business Line. However, if you try browsing to the site with Elinks, you'll notice that, barring the top hyperlinks in each sectcion, the links on the left are not "linked" at all.

In addition, there are some other irritants which are easy to remove, such as the navigation bar on the top, and the text colour being too light for my taste etc. So, I write the following Lua blurb. Why I write this is left for the interested readers to figure out, though it shouldn't be surprising if you open the page. The workaround for the missing links is interesting, though; it is because the website authors have put a hyperlink (<a>) tag before a list item (<li>) tag, and Elinks seems to not like that too much. So, I just swap the two around, and Elinks is happy.

-- Reformat the Business Line website
function blonnet_format_html_hook (html)
   html = string.gsub(html, "<body ", '<body text="#000000"') -- I like the text in black on the white background
   html = string.gsub(html, "<[Ff][Oo][Nn][Tt] class=leftnavi color=brown>.-</[Ff][Oo][Nn][Tt]>", '') -- An ugly hack to remove the navigation bar
   html = string.gsub(html, "<TD align=left vAlign=top width=\"500\"><IMG.-</FONT><BR>", '', 1) -- Remove description
   html = string.gsub(html, "<A class=groupnavi href=\"http://epaper.thehindubusinessline.com/\">.-</FONT><BR>", '', 1) -- Remove other group links
   html = string.gsub(html, "(<[Aa] class=navi.-)<li>(.-</[Aa]>)", "<li>%1%2</li>") -- Fix the erroneous section sidebar
   return html
end

function pre_format_html_hook (url, html)
   if sstrfind (url, "blonnet.com") or sstrfind(url, "thehindubusinessline.com") then
      return blonnet_format_html_hook(html)
   elseif sstrfind (url, "bugs.debian.org") then
      return debian_bts_format_html_hook(html)
   elseif sstrfind (url, "mobile.twitter.com") then
      return mobile_twitter_format_hook(html)
   end
   return nil
end

And here's the old and new rendering:

So, I have finally visited my first Debconf, and it was a phenomenal experience. To meet persons who have guided you, persons work with, and persons you respect face-to-face and have conversations with them about several topics ranging from their vision for Debian to their views on topics totally unrelated to software is something truly great. I am now convinced that events like this, which provide the right environment to socialize and discuss various issues concerning Debian, will go a long way into getting several aspects of the project moving along in the right directions, as well as create awareness to the outside world about what the project is about and how it benefits users.

In terms of discussions, the Debian Science track was a nice way to see how contributors are putting Debian to good use for scientific research, and it was a nice opportunity to list out the things to be done to fill in the gaps and take Debian as a science platform forward. The Debian Python BoF was also a good place to meet many contributors face-to-face, and learn more about the technical concerns which people have in regard to the future of Python in Debian.

While I didn't hack much during the conference, Christian's presence made me finish the Hindi translation of the Debian Installer. We can now shift focus to other aspects, such as getting packages in order for a short freeze-to-release cycle.

Columbia University provides for a very nice venue, with easy access while maintaining a quaint environment within itself. Since this is my second visit to New York City, I had an idea of the common tourist locations, so I did not go around much during the conference. However, since I have a buffer day, I might try my hand at some photography around the place.

Have a safe trip home, and a wonderful time ahead! I leave you with a photo I took when I went with a friend across the Brooklyn Bridge after Debconf.

So, I will be at DebConf10 from 4th August onwards. The prime purpose of my visit is to meet all Debian developers, so I don't think the delayed attendance should matter much.

Customary banner:

See you all there!

So, I will be at DebConf10 from 4th August onwards. The prime purpose of my visit is to meet all Debian developers, so I don't think the delayed attendance should matter much.

Customary banner:

See you all there!

So, while Richard is busy doing research and arranging or facilitating several Debian workshops, here I am, gulping down Idlis and Dosas by the dozen. It's been a fun visit, and I got to visit several places in my native state, but since my visit to Mumbai is rather short, I won't be able to say hello to several friends this time (Sorry Kartik). Maybe this would happen only when I am back in India on a permanent basis; let's see...

Here are some general guidelines for travelers which I'd like to share:

• They say it doesn't snow in Dallas. Don't believe them. I had to stay overnight at Dallas, and then embark on a trip in the other direction (trans-Pacific) to get home. It wasn't a really fun journey.
• If you're ever rerouted due to flight delays, ensure you travel by a similar route, or else, ensure that you're not a vegetarian/vegan. If you fly to Tokyo and Hong Kong, for instance, be sure that you've specified your meal choices well in advance. Of course, you can live on fruits and bread, but you'll really be doing yourself a favour by not missing your flights in the first place; I don't know how I have wronged the weather gods this time.
• Ensure that you don't keep too many valuables (which Customs might be suspicious of) in your checked-in baggage. This is important, especially to get through situations where you find that your baggage doesn't arrive with you (my baggage came a day late, and, thankfully, cleared customs quickly since my clothes were duty free, thanks to the many heavy duty cycles they've gone through in washing machines).

It's been a really fun trip, and I am sure I'll enjoy the rest of the trip, till I get back to my old routine and resume work.

Finally, in keeping with the spirit of a blog I try to understand (albeit, in vain, I must accept), I duplicate the concept of a post from that blog, here is an up-to-date list of airports in which I have sat, but never left except by way of airplane:

• LGW
• IDR
• EWR
• CLT
• TKO
• HKG

More updates later. Bye for now.

(English translation below. Indian Debian community, please spread the word!)

डेबियन का उपयोग करने वाले मेरे साथियों! शायद आपको पता नहीं, पर डेबियन के कई अंश कई भारतीय भाषाओं में उपलब्ध है, और KDE, GNOME और अन्य कई प्रोग्राम पूरी तरह हिंदी में उपलब्ध हैं. यह कई लोगों की स्वेच्छापूर्वक सहयोग द्वारा ही संभव हो पाया है. इसमें डेबियन संस्थापक (Debian Installer) के वाक्यों का अनुवाद Lenny से लेकर अब तक मैं करता आ रहा हूँ, और आगे भी करता रहूँगा. पर सब की तरह मेरा समय, और हिंदी में तकनीकी शब्दों का मेरा ज्ञान, दोनों सीमित हैं. इसलिए, मैं डेबियन का उपयोग करने वाले मेरे साथियों से अनुरोध करता हूँ की, अगर आपके पास समय हो, तो कृपया डेबियन संस्थापक के वाक्यों के अनुवाद में मेरी सहायता करें. ऐसा करने से आप प्रसिद्ध होने के साथ साथ डेबियन के हिंदी उपयोगकर्ताओं की कृतज्ञता भी प्राप्त कर सकेंगे!

अनुवाद में हाथ बंटाने के लिए हिंदी में प्रवीण होने की आवश्यकता नहीं है; केवल हिंदी का व्यवहारिक ज्ञान और ज़रा समय देना हमारे लिए काफी लाभदायक होगा.

अधिक जानकारी के लिए संपर्क कीजिये: akumar@डेबियन.ओर्ग (अंग्रेजी में) ;-)

धन्यवाद!

Translation

Fellow Debian users (who know Hindi)! Maybe you aren't aware yet, but several parts of Debian have been localized and are available in several Indian languages, and KDE and GNOME and several programs are available natively in those languages. This has been possible only due to dedicated volunteers spending time in translating the programs. I have been translating the strings in the Debian Installer to Hindi, since Lenny, and will continue with the translations. But like others, I am short on both time, and my knowledge of technical Hindi words and phrases is limited. So, I'd request fellow users to chip in with some translations to the Debian Installer strings, if they have the time. That way, not only will you earn fame and glory, you'll also earn the gratitude of the Hindi Debian user community.

You don't need to be an expert in the language and grammar to help out with the translations. All you need is some working Hindi knowledge and a bit of time.

For more information, email me at akumar followed by debian.org

Thank you!