Bash: Custom keyboard shortcuts

Are you bored of typing ls all the time in your terminal. Wouldn't be greate if you could just hit a shortcut? You are in luck, because you just can. No addon, no nothing, just with the built-in bind:

bind '"\el":"ls -thor\n"'

Here you just bind Alt-L to run ls -thor.

done_

Javascript: Avoiding the JsDoc

 We all want the types of Typescript without the Typescript, for the best friend to every human code generator: the members suggestion list that shows up after the dot.

But when you initilize a member with null in a Javascript class, obviusly the type infernece has no clue, so you need to add that JsDoc comment above:

constructor() {
  /** @type {Thing} */
  this.thing = null;
  /** @type {OtherThing} */
  this.target = null;
}

Yeah... adding a bunch of them after a while is not so elegant, breaks the flow, and also the verbosity doesn't realy help. Let's move the information from the comments to the actual code.

So we need something, like a function, that says that returns an object of a type, but just returns null, that also must be given the class, passing the class literal. Just, lookup how to denote a class, then add the JsDoc just there once to make it work:

/**
 * @template T
 * @param {new (...args: any[]) => T} c
 * @returns {T}
 */
function null_of(c) {
  return null;
}

And rewrite the constructor with it:

constructor() {
  this.thing = null_of(Thing);
  this.target = null_of(OtherThing);
}

done_

Techniques: Patch files

Create a patch file:

• Locate the file we want to change, eg. path/file.json
• Create a copy of the file and edit it in the same directory, eg. path/file.new.json
• Create the diff file by running the program diff, eg.

  diff -u path/file.json path/file.new.json > file.json.diff

• Ensure or change the first lines of the diff file in order to point to the desired files, eg. path/file.json to build/path/file.json
• Apply the patch by running the program patch, eg.

  patch -p0 < file.json.diff

Notes:

• Both programs, diff and patch, should be part of the core programs on any linux distribution
• The -u option specifies that the created file is of unified type
• The -p0 options specifies that the full paths inside the first lines of the diff file should be used

done_

Html: Enter handler on input text field

Every single time you have a input text field and submit-like button next to it, at some point, you would like to bind the same action of the submit button to the press of the enter key.

It's trivial, but also it's simply better to just copy-paste it. So here its is:

function onenter(ele, f) {
	ele.addEventListener('keydown', function (e) {
		if (e.keyCode === 13) { f(e); e.preventDefault(); }
	})
}

And also while we are here, instead of using the-not-be-named lib, just use these:

function q(x) { return document.querySelector(x); }
function qa(x) { return [...document.querySelectorAll(x)]; }
function range(x) { return Array.from({length: x}, (v, i) => i); }

For more just go here.

done_

Python: Easy help print

As a follow up of the "Bash: Easy help print", lets do the same thing. So I will just copy the whole text and replace what needs replacing...

Ok, lets create a single line of python that will handle the -h option and print something.

First, what to print? I usually add some comments on the start of the file, so lets print that. Example script:

#!/bin/env python3
#
#  This is the doc of the script
#

the line that we will add

code of script

Lets go step by step. We need to print the file it self:

h = open(args[0], 'r').read()
print(h)

Skip the first line (lets skip the read):

print(h[h.index('\n')+1:])	

Go until you find the first empty line:

print(h[h.index('\n')+1:h.index('\n\n')]

Remove the # fro the start of the line:

.replace('#','')

Finally, we check if the -h is the first argument, print the thing and exit:

if '-h' in args: h = open(args[0], 'r').read(); print(h[h.index('\n')+1:h.index('\n\n')].replace('#','')); exit()

done_

Html: Input tag drop-down list

The classic way to have a drop-down list in html is the select tag.

However there are two main problems/inconvenient. The select tag will only allow to select one item and you cannot type for a not included option or just to filter the list options. Also sometimes just have all the input fields under the same tag name <input> is just niter.

An other way is the <datalist>, that for some reason I learned about it lately (sad).

The classic example:

<input list="hashes">
<datalist id="hashes">
  <option value="sha1">
  <option value="sha256">
  <option value="sha512">
</datalist>

done_ 

Python: Easy line plots

Need to just plot a file with numbers? Stop using matl@b or exc€l.

All we need is a couple lines of Python code:

import matplotlib.pyplot as p

p.plot(values)
p.show()

And for the values (if you have the number with new-line separating them) with either a file as an argument of just the stdin couple more lines:

import sys

stream = sys.stdin
if len(sys.argv) > 1:
    stream = open(sys.argv[1], 'r')

values = [float(line) for line in stream]

done_

Bash: Easy help print

Ok, lets create a single line of bash that will handle the -h option and print something.

First, what to print? I usually add some comments on the start of the file, so lets print that. Example script:

#!/bin/bash
#
#  This is the doc of the script
#

the line that we will add

code of script

Lets go step by step. We need to print the file it self:

cat "$0"

Skip the first line (lets switch to sed):

sed -n '2,$ p' "$0"

Go until you find the first empty line:

sed -n '2,/^$/ p' "$0"

Remove the # fro the start of the line:

sed '2,/^$/ s/#// p' "$0"

Finally, we check if the -h is the first argument, print the thing and exit:

[ "$1" = '-h' ] && sed -n '2,/^$/ s/#// p' "$0" && exit

done_

Android: Send preset SMS with with one tap

For all of you that need to sent a simple preset SMS without copy pasting all the time (covid-era).

For some reason on the play store most of the app that provide this kind of operation instead of sending the SMS they just open the messages app...

Ok, lets do it:

SmsManager smsManager = SmsManager.getDefault();
smsManager.sendTextMessage("phone_number", null, "message", null, null);

And because this android we need to haggle with the permissions:

<uses-permission android:name="android.permission.SEND_SMS" />

if (ContextCompat.checkSelfPermission(this, Manifest.permission.SEND_SMS) 
		!= PackageManager.PERMISSION_GRANTED) {
	ActivityCompat.requestPermissions(this, new String[] {
    		Manifest.permission.SEND_SMS}, 0);
}

And we are done, that's it.

done_

Java: Let's serialize with a map

Lets just use a map. So we have a timer like thing:

public class Time implements Serializable {

    private long duration;
    private long start;

    // crazy things

}

Now lets put everything in a map:

    private void writeObject(java.io.ObjectOutputStream out) throws ... {
        Map map = new HashMap<>();

        map.put("duration", duration);
        map.put("start", start);
        out.writeObject(map);
    }

Now lets get everything back from the map:

    private void readObject(java.io.ObjectInputStream in) throws ... {
        Map map = (java.util.Map) in.readObject();

        duration = (long) map.get("duration");
        start = (long) map.get("start");
    }

Lets also put this because we are handling the versioning:

    public static final long serialVersionUID = 1L;

However this is too much stuff to write, so lets make a script to write it for us: https://maanoo.com/testing/JavagenSerialMap.html

Now lets add a new thing to see how to handle versioning

    private TimeUnit unit;  // v.2

So we have to update the things: (our script that is)

    private void writeObject(java.io.ObjectOutputStream out) throws ... {
        Map map = new HashMap<>();

        map.put("duration", duration);
        map.put("start", start);
        map.put("unit", unit);
        out.writeObject(map);
    }

    private void readObject(java.io.ObjectInputStream in) throws ... {
        Map map = (Map) in.readObject();

        duration = (long) map.get("duration");
        start = (long) map.get("start");
        if (map.containsKey("unit")) {
            unit = (TimeUnit) map.get("unit");
        } else {
            // TODO unit
        }
    }

And we replace the TODO by setting the default value of the unit:

    unit = TimeUnit.Milliseconds

Also, if or when we are sure that there is none of the old version left, we can remove the check of the key and remove the setting of the default value.

Except the full control that this system provides, the actual data that are stored are serialized primitives and collections, making possible to be access and/or debug the saved data by external program.



done_

Java: Iterable iterator

We all have been in a position with an Iterator in our hands and trying to pass it to a for each loop. And then for some reason that is totally crazy for a second an error pops up:

"Can only iterate over an array or an instance of java.lang.Iterable"

What... a ok... and then what? You could just fix your logic in order or just google for "java iterator to iterable". But could you just make the iterator also an iterable somehow.

Step one, obviously, add the Iterable interface to your iterator:

public class SuperIterator<T> implements Iterator<T>, Iterable<T> {

Step two, add the missing method by return itself as its iterator:

@Override
public Iterator<Character> iterator() {
    return this;
}

done_

Windows: Copy only what's new or changed

Copy all files (/H /G) and directories (/E) that are either new or changed (/D /Y)

xcopy C:\From C:\To /D /E /I /H /Y /G

done_

Java: Open link in browser

Open a link with the default browser:

Desktop.getDesktop().browse(new URL("http://maanoo.com").toURI());

done_

Javascript: Canvas circles

So we always start:

var canvas = document.getElementById("canvas");
var c = canvas.getContext("2d");

and we have the basic:

c.fillRect
c.fillText
c.strokeRect
c.strokeText

and for all other shapes we use paths

I use a lot of circles so why not add:

c.fillCircle
c.strokeCircle

We can do that by adding some functions to the prototype of the c with is the CanvasRenderingContext2D:

CanvasRenderingContext2D.prototype.fillCircle = function(x, y, r) {
  this.beginPath();
  this.arc(x, y, r, 0, 2 * Math.PI);
  this.fill();
};

CanvasRenderingContext2D.prototype.strokeCircle = function(x, y, r) {
  this.beginPath();
  this.arc(x, y, r, 0, 2 * Math.PI);
  this.stroke();
};

done_

Android: Store values

We can save and load values, permanently, using Shared Preferences.

The shared preferences framework provides an easy way to store values, not only preference related but any kind of values. It's a file based so keep that in mind.

To get the SharedPreferences object we need:

private static final String NAME = "...";
public static SharedPreferences getPreferences(Activity a) {
  return a.getSharedPreferences(NAME , Context.MODE_PRIVATE);
}

To save a values we:

public static void save(Activity a) {
  SharedPreferences.Editor sp = getPreferences(a).edit();

  sp.putString("name1", value1);
  sp.putInt("name2", value2);

  sp.commit();
}

And to load a values we:

public static void load(Activity a) {
  SharedPreferences sp = getPreferences(a);

  value1 = sp.getString("name1", default1);
  value2 = sp.getInt("name2", default2);
}

We can also get a single Preferences for each activity with:

getPreferences(Context.MODE_PRIVATE)

Except MODE_PRIVATE we have MODE_WORLD_READABLE and MODE_WORLD_WRITEABLE which are deprecated, so don't use them.


done_

JavaScript: Local and Session storage

To store values to a browser we can use localStorage and sessionStorage just by:

localStorage["name"] = value;

and to get the values we just:

value = localStorage["name"];

The localStorage keeps the values for ever (probably).

The sessionStorage keeps the values until the page session ends.

For each domain our browser has a pair of these objects and not for each page.

To store objects without functions we use JSON:

localStorage["name"] = JSON.stringify(object);

object = JSON.parse(localStorage["name"]);

done_

JavaScript: jQuery selector

If we want to use JQuery ONLY for selecting elements like:

$(".item")

Why use a whole library, just:

document.querySelectorAll(".item")

or

function q(query) {
  return document.querySelectorAll(query);
}

q(".item")

Note: The only thing we gain from this is self-something.


continue_

PHP: Simple counter

A simple counter using a text file.

The php code:

<?php
  $path = "./counter.txt";
  $count = intval(file_get_contents($path));
  if(isset($_GET["add"])) {
    $count++;
    file_put_contents($path, $count);
  }
  echo $count;
?>

To add one to the counter must be called with GET parameter add.

To get the counter value must be called with no parameters.


done_

CSS: Transition all

In CSS if we define transitions, every time a value changes an animation-transition is created and executed.

So if we want to use transitions for all elements and for all values (which is wrong in many ways), we can just write:

*{
  transition: all 0.7s ease-in-out;
}

done_

Code: Normalize overflowing values

To normalize values like degrees where the main range is [0, 360) but all other values are accepted too the obvious is:

value = value % 360

Which  in case of a [min, max) range is:

value = (value - min) % (max - min) + min

But when the value is a negative number or even smaller than the min we get wrong result.
What we can do is "overflow" the value one more time:

value = ((value % 360) + 360) % 360

Which  in case of our generic [min, max) range is:

value = ((value - min) % (max - min) + max - min) % (max - min) + min

In an extended form:

len = max - min
value = ((value - min) % len + len) % len + min

done_