Bash provides many important built-in commands, like ls, cd, and mv, as well as regular tools such as grep, awk, and sed. But, it is equally important to know the punctuation marks — the glue in the shape of dots, commas, brackets. and quotes — that allow you to transform and push data from one place to another. Take angle brackets (< >), for example.

Pushing Around

If you are familiar with other programming and scripting languages, you may have used < and > as logical operators to check in a condition whether one value is larger or smaller than another. If you have ever written HTML, you have used angle brackets to enclose tags.

In shell scripting, you can also use brackets to push data from place to place, for example, to a file:

ls > dir_content.txt

In this example, instead of showing the contents of the directory on the command line, > tells the shell to copy it into a file called dir_content.txt. If dir_content.txt doesn’t exist, Bash will create it for you, but if dir_content.txt already exists and is not empty, you will overwrite whatever it contained, so be careful!

You can avoid overwriting existing content by tacking the new stuff onto the end of the old stuff. For that you use >> (instead of >):

ls $HOME > dir_content.txt; wc -l dir_content.txt >> dir_content.txt

This line stores the list of contents of your home directory into dir_content.txt. You then count the number of lines in dir_content.txt (which gives you the number of items in the directory) with wc -l and you tack that value onto the end of the file.

After running the command line on my machine, this is what my dir_content.txt file looks like:

Applications bin cloud Desktop Documents Downloads Games ISOs lib logs Music OpenSCAD Pictures Public Templates test_dir Videos 17 dir_content.txt

The mnemonic here is to look at > and >> as arrows. In fact, the arrows can point the other way, too. Say you have a file called CBActors containing some names of actors and the number of films by the Coen brothers they have been in. Something like this:

John Goodman 5

John Turturro 3

George Clooney 2

Frances McDormand 6

Steve Buscemi 5

Jon Polito 4

Tony Shalhoub 3

James Gandolfini 1

Something like

sort < CBActors # Do this

Frances McDormand 6 # And you get this

George Clooney 2 James Gandolfini 1 John Goodman 5 John Turturro 3 Jon Polito 4 Steve Buscemi 5 Tony Shalhoub 3

Will sort the list alphabetically. But then again, you don’t need < here since sort already expects a file anyway, so sort CBActors will work just as well.

However, if you need to see who is the Coens’ favorite actor, you can check with :

while read name surname films; do echo $films $name $surname > filmsfirst.txt; done < CBActors

Or, to make that a bit more readable:

while read name surname films;\ do echo $films $name $surname >> filmsfirst;\ done < CBActors

Let’s break this down, shall we?

• the while ...; do ... done structure is a loop. The instructions between do and done are repeatedly executed while a condition is met, in this case…
• … the read instruction has lines to read. read reads from the standard input and will continue reading until there is nothing more to read…
• … And as standard input is fed in via < and comes from CBActors, that means the while loop will loop until the last line of CBActors is piped into the loop.
• Getting back to read for a sec, the tool is clever enough to see that there are three distinct fields separated by spaces on each line of the file. That allows you to put the first field from each line in the name variable, the second in surname and the third in films. This comes in handy later, on the line that says echo $films $name $surname >> filmsfirst;\, allowing you to reorder the fields and push them into a file called filmsfirst.

At the end of all that, you have a file called filmsfirst that looks like this:

5 John Goodman 3 John Turturro 2 George Clooney 6 Frances McDormand 5 Steve Buscemi 4 Jon Polito 3 Tony Shalhoub 1 James Gandolfini

which you can now use with sort:

sort -r filmsfirst

to see who is the Coens’ favorite actor. Yes, it is Frances McDormand. (The -r option reverses the sort, so McDormand ends up on top).

We’ll look at more angles on this topic next time!

Among the surprise announcements during today’s Nintendo Indie Highlights presentation was Goat Simulator: The GOATY. It’s available to play on Switch as we speak.

That’s right, everyone’s favourite game about possessing the body of a goat, exploring an open, suburban world, bashing into everything in sight, and occasionally giving things a good lick is now on Switch. As the small clip from the presentation states, it’s bringing “next-gen goat simulation” to a console near you.

The trailer shows you the exact kind of madness you can expect to find in the game, and the Switch version includes all DLC released for the title on other platforms.

You can pick the bundle up right now from the Switch eShop for £26.99 / $29.99.

Are you snapping this one up immediately? Is Goat Simulator perhaps not your thing? Tell us below.

August 21, 2019

Hilton San Diego Bayfront

San Diego, CA 92101

United States

Embedded Linux Conference (ELC) is the premier vendor-neutral technical conference where developers working on embedded Linux and industrial IoT products and deployments gather for education and collaboration, paving the way for innovation. Attend, and join 800+ technical experts paving the way for transformation in these key areas from across the globe for education, collaboration and deep dive learning opportunities.

For the first time in 2019, Embedded Linux Conference North America will co-locate with Open Source Summit North America. Learn More

Click Here!

When disaster hits, be it a natural disaster, epidemic, poverty or other crisis, first responders rely on GIS data to access the areas impacted.

Missing Maps is an open-source collaborative effort founded by the American Red Cross, British Red Cross, Medicine Sans Frontiers, and the Humanitarian OpenStreetMap team where volunteers help to map areas in an effort to ensure that many of the places previously missing from maps can be located and reached.

Millions of edits are made to OpenStreetMap by thousands of volunteers and members of the OpenStreetMap community.

Moved by the Missing Maps objective, “To map the most vulnerable places in the developing world, in order that international and local NGOs and individuals can use the maps and data to better respond to crises affecting the areas,” teams at Microsoft are contributing time, resources and technical expertise to the project.

Since initiating the program at Microsoft, over four thousand employees have been trained in contributing to OpenStreetMap at hundreds of mapathons across the company. With the goal to “put 200 million people ‘on the map’ by 2021,” we hope you are inspired to get involved too! 

To learn more about Missing Maps and to start mapping, go to www.missingmaps.org. 

– Bing Maps Team