Terminal Friday: Bash [Key Expansion]

First of all I would like to apologize, since last Friday I could not write the post so today I will add an extra to make up the lost day. 🙂

Brace Expansion

In Spanish key expansion seems to me to be a function inspired by C Shell, this generates combinations between the characters that are entered inside the braces, the order it uses is from left to right. It is not complicated at all, but it is an option that will be very useful in our tours of GNU / Linux.

Example:

$ echo a {1,2,3} a1 a2 a3

When used with commas (,) generates combinations between the value a and the values ​​inside the braces. If there were no value outside the keys, it would only show once each value that the key contains.

$ echo {a, b, c} abc

Its use is not complex at all, there are other more common examples such as creating many directories in a folder

$ mkdir ~ / Jobs / {one, two, three, four, five}

This creates five folders within the jobs folder, it's like entering one command at a time. Creating the 5 directories.

There are expansion by two points .. This creates a series of numbers or characters that go from the initial value to the final value, do not use lettered numbers.

$ echo {1..5} #Correct 1 2 3 4 5 $ echo {a..f} #Correct abcdf $ echo {a..5} #Incorrect {a..5} #I think I'll never get used to this blue color in letter

We can save time by creating a cycle for

#Instead of writing $ for ((i = 1; i <= 5; i ++)); do echo "My number $ i"; done My number 1 My number 2 My number 3 My number 4 My number 5 #Save code using brace expansion. $ for i in {1..5}; do echo "My number $ i; done My number 1 My number 2 My number 3 My number 4 My number 5 #Of course it is valid to use although the output is different. $ echo" My number "{1..5} My number 1 My number 2 My number 3 My number 4 My number 5

Well I think the concept is clear, haha ​​now I will only comment that it is combinable and nested. What do I mean by this?
With combinable to which we can join one or more keys

$ echo {a..c} {1..3} a1 a2 a3 b1 b2 b3 c1 c2 c3

With nesting as many would imagine you can use expansion keys within expansion keys

$ echo {a, c {1..3}, d} a c1 c2 c3 d

And finally from Bash NOTHING it is possible to increase the values.

$ echo {0..20..2} 0 2 4 6 8 10 12 14 16 18 20

This is all for today, so thanks for reading me people 🙂

Extras

How to create a local bin

When I say a bin local I mean a directory in which we have our own scripts and it is possible to execute them as a simple command ...

Achieving this is relatively easy, the first thing you need to do is create a directory where we will save the scripts.

mkdir ~ / .bin # In this example it will be hidden

Now we have our folder to save the scripts but it won't work until we add the path of the new .bin to $ PATH
For this the file is edited bash_profile, and the line is added.

export PATH = $ PATH: ~ / .bin

And voila that is enough to create a local bin, of course it will ask for root permissions if necessary for an example we write a quick script.

#! / bin / bash echo "Hi $ 1, how are you?"

Save it with the name of Hello
The script is given execution permission and it will only be enough to call it from the terminal

$ hello wada # This will show the message Hello wada, how are you?

So with this quick trick you can run your scripts faster

That's all for today people who are well 🙂
PS Sorry for mistakes if there are, my eyes are already closing hahaha 😀