Work the Shell - Generating Turn-by-Turn Driving Directions
I'm happy to report that this month, I'm answering a reader's question about how to script something. Dunno what's up with the rest of you readers, but apparently writing to me with your weird and challenging shell-scripting puzzles isn't making the short list right now. Reader Paul M. asks:
Ah, those tricky programmers over at Google Maps make this pretty darn difficult! Poke around at the source pages generated by maps.google.com looking for directions, and it's clear that they're using a method=post or other advanced way to hide the starting and ending points from the URL itself, along with some very fancy coding to make the Web pages highly interactive. So to heck with it!
After much digging around and looking at how the different mapping sites work, I settled on Expedia.com as the best place to get driving directions so that we'll be able to specify start and stop points via URL and also understand the output. To get started, check out Expedia's interactive driving directions in your Web browser at www.expedia.com/Directions.
On Expedia, enter a starting and ending address for directions, and you'll find that it's all stored in a scary-complex URL like this: www.expedia.com/pub/agent.dll?qscr=mrdr&rtyp=0&unit=0&lats1=38.89872&lons1=-77.036379&alts1=5&strt1=1600+Pennsylvania+Ave+NW&city1=Washington&stnm1=DC&zipc1=20006®n1=0&labl1=1600+Pennsylvania+Ave+NW%2C%0AWashington%2C+DC+20006&lats2=28.393142483519902&lons2=-81.57198620078931&alts2=5&strt2=N+World+Dr&city2=Orlando&stnm2=FL&zipc2=32830®n2=0&labl2=World+Dr%2C%0AOrlando%2C+FL+32830&. (Eagle-eyed readers will notice that I'm offering the Obama family driving directions to Disney World.)
You can strip some of the superfluous information out of the URL and create a simple command-line call to get the map and directions:
start="strt1=1600+Pennsylvania+Ave+NW&city1=Washington&stnm1=DC" dest="strt2=N+World+Dr&city2=Orlando&stnm2=FL&zipc2=32830" curl --silent "http://www.expedia.com/pub/agent.dll?$start& ↪$dest&qscr=mrdr&rtyp=0&unit=0"
You can see that Expedia wants an address unwrapped and split by street address, city, state and zip code (though if it can figure out the location, it appears you can skip the zip code, as shown in start above).
Now that we have that, let's use sed to extract just the table of results, without the other superfluous information. This is done by manual analysis of the source file and noting that it's all in a table that starts with this HTML line:
<TABLE BORDER=1 BORDERCOLOR=#E4E4E4 CELLSPACING=0 CELLPADDING=4>
Not surprisingly, the line we seek that denotes the end of the table is </TABLE>. Here's the code that lets you slice things as desired:
sed -n '/BORDERCOLOR=#E4E4E4/,/<\/TABLE>/p'
Put them all together and save the output to a temp file. After that, the next challenge is to turn that HTML table into something you actually can read.
To do that, we're going to turn to a great open-source utility called Lynx. You might already have Lynx on your system, but if you don't, grab a copy of the Lynx text-based Web browser from lynx.isc.org. We'll use that to interpret and convert the HTML markup to raw text.
Fortunately, Lynx excels at this kind of challenge, as demonstrated by the working code:
curl --silent "http://www.expedia.com/pub/agent.dll?$start& ↪$dest&qscr=mrdr&rtyp=0&unit=0"| \ sed -n '/BORDERCOLOR=#E4E4E4/,/<\/TABLE>/p' | \ lynx -dump -stdin
Yup, that's it. Specify a correct start and destination, make sure that the script knows where to find Lynx on your system, and the output will look like this:
Directions Distance Time Start: Depart Start on Local road(s) (East) 0.1 < 1min 1: Turn RIGHT (South) onto E Executive Ave NW 0.1 0:01 2: Turn LEFT (East) onto Alexander Hamilton Pl NW, then immediately turn RIGHT (South) onto 15th St NW 0.1 0:01 3: Turn LEFT (East) onto Pennsylvania Ave NW, then immediately turn RIGHT (South) onto 14th St NW 0.3 0:02 4: Keep STRAIGHT onto US-1 [14th St NW] 1.1 0:02 ... 22: Take Ramp (LEFT) onto Western Way (Disney World) 1.9 0:02 23: Turn LEFT (North) onto Bear Island Rd 2.1 0:03 24: Turn RIGHT (East) onto Floridian Way 0.3 0:01 25: Keep STRAIGHT onto World Dr 0.4 0:01 End: Arrive End < 0.1 < 1min Total Route 881 mi 13 hrs 2 mins
I'll leave it as an exercise to you, dear reader, to create a wrapper that prompts people for starting and ending addresses and then uses the curl invocation to Expedia and subsequent invocation of Lynx to display turn-by-turn driving directions.
Dave Taylor has been hacking shell scripts for a really long time, 30 years. He's the author of the popular Wicked Cool Shell Scripts and can be found on Twitter as @DaveTaylor and more generally at www.DaveTaylorOnline.com.
Dave Taylor has been hacking shell scripts for over thirty years. Really. He's the author of the popular "Wicked Cool Shell Scripts" and can be found on Twitter as @DaveTaylor and more generally at www.DaveTaylorOnline.com.
Practical Task Scheduling Deployment
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
Join Linux Journal's Mike Diehl and Pat Cameron of Help Systems.
Free to Linux Journal readers.View Now!
|The Firebird Project's Firebird Relational Database||Jul 29, 2016|
|Stunnel Security for Oracle||Jul 28, 2016|
|SUSE LLC's SUSE Manager||Jul 21, 2016|
|My +1 Sword of Productivity||Jul 20, 2016|
|Non-Linux FOSS: Caffeine!||Jul 19, 2016|
|Murat Yener and Onur Dundar's Expert Android Studio (Wrox)||Jul 18, 2016|
- Stunnel Security for Oracle
- The Firebird Project's Firebird Relational Database
- Murat Yener and Onur Dundar's Expert Android Studio (Wrox)
- SUSE LLC's SUSE Manager
- Managing Linux Using Puppet
- My +1 Sword of Productivity
- Non-Linux FOSS: Caffeine!
- Doing for User Space What We Did for Kernel Space
- SuperTuxKart 0.9.2 Released
- Google's SwiftShader Released
With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide