web/_posts/2019-08-08-write-a-new-post.md

---
title: Writing a New Post
author:
  name: Cotes Chung
  link: https://github.com/cotes2020
date: 2019-08-08 14:10:00 +0800
categories: [Blogging, Tutorial]
tags: [writing]
render_with_liquid: false
---

This post will guide you how to write a post on _Chirpy_ theme. Even if you have previous experience with Jekyll, this article is worth reading, because many features require specific variables to be set.

## Naming and Path

Create a new file named `YYYY-MM-DD-TITLE.EXTENSION` and put it in the `_posts` of the root directory. Please note that the `EXTENSION` must be one of `md` and `markdown`. If you want to save time of creating files, please consider using the plugin [`Jekyll-Compose`](https://github.com/jekyll/jekyll-compose) to accomplish this.

## Front Matter

Basically, you need to fill the [Front Matter](https://jekyllrb.com/docs/front-matter/) as below at the top of the post:

```yaml
---
title: TITLE
date: YYYY-MM-DD HH:MM:SS +/-TTTT
categories: [TOP_CATEGORIE, SUB_CATEGORIE]
tags: [TAG]     # TAG names should always be lowercase
---
```

> **Note**: The posts' _layout_ has been set to `post` by default, so there is no need to add the variable _layout_ in the Front Matter block.

### Timezone of Date

In order to accurately record the release date of a post, you should not only set up the `timezone` of `_config.yml` but also provide the post's timezone in variable `date` of its Front Matter block. Format: `+/-TTTT`, e.g. `+0800`.

### Categories and Tags

The `categories` of each post are designed to contain up to two elements, and the number of elements in `tags` can be zero to infinity. For instance:

```yaml
categories: [Animal, Insect]
tags: [bee]
```
### Author Information

The author information of the post usually does not need to be filled in the _Front Matter_ , they will be obtained from variables `social.name` and the first entry of `social.links` of the configuration file by default. But you can also override it as follows:

```yaml
---
author:
  name: Full Name
  link: https://example.com
---
```

## Table of Contents

By default, the **T**able **o**f **C**ontents (TOC) is displayed on the right panel of the post. If you want to turn it off globally, go to `_config.yml` and set the value of variable `toc` to `false`. If you want to turn off TOC for a specific post, add the following to the post's [Front Matter](https://jekyllrb.com/docs/front-matter/):

```yaml
---
toc: false
---
```

## Comments

Similar to TOC, the [Disqus](https://disqus.com/) comments are loaded by default in each post, and the global switch is defined by variable `comments` in file `_config.yml` . If you want to close the comment for a specific post, add the following to the **Front Matter** of the post:

```yaml
---
comments: false
---
```

## Mathematics

For website performance reasons, the mathematical feature won't be loaded by default. But it can be enabled by:

```yaml
---
math: true
---
```

## Mermaid

[**Mermaid**](https://github.com/mermaid-js/mermaid) is a great diagrams generation tool. To enable it on your post, add the following to the YAML block:

```yaml
---
mermaid: true
---
```

Then you can use it like other markdown languages: surround the graph code with ```` ```mermaid ```` and ```` ``` ````.

## Images

### Preview image

If you want to add an image to the top of the post contents, specify the attribute `src`, `width`, `height`, and `alt` for the image:

```yaml
---
image:
  src: /path/to/image/file
  width: 1000   # in pixels
  height: 400   # in pixels
  alt: image alternative text
---
```

Except for `alt`, all other options are necessary, especially the `width` and `height`, which are related to user experience and web page loading performance. Later section ["Image size"](#image-size) will also mention this.

Starting from _Chirpy v4.4.0_, the attributes `height` and `width` support abbreviations: `height` → `h`, `width` → `w`.


### Image caption

Add italics to the next line of an image，then it will become the caption and appear at the bottom of the image:

```markdown
![img-description](/path/to/image)
_Image Caption_
```
{: .nolineno}

### Image size

In order to prevent the page content layout from shifting when the image is loaded, we should set the width and height for each image:

```markdown
![Desktop View](/assets/img/sample/mockup.png){: width="700" height="400" }
```
{: .nolineno}

Starting from _Chirpy v4.4.0_, `height` and `width` support abbreviations (`height` → `h`, `width` → `w`). The following example has the same effect as the above:

```markdown
![Desktop View](/assets/img/sample/mockup.png){: w="700" h="400" }
```
{: .nolineno}

### Image position

By default, the image is centered, but you can specify the position by using one of the classes `normal`, `left`, and `right`. For example:

- **Normal position**

  Image will be left aligned in below sample:

  ```markdown
  ![Desktop View](/assets/img/sample/mockup.png){: .normal }
  ```
  {: .nolineno}

- **Float to the left**

  ```markdown
  ![Desktop View](/assets/img/sample/mockup.png){: .left }
  ```
  {: .nolineno}

- **Float to the right**

  ```markdown
  ![Desktop View](/assets/img/sample/mockup.png){: .right }
  ```
  {: .nolineno}

> **Limitation**: Once the position of the image is specified, the image caption should not be added.

### Image shadow

The screenshots of the program window can be considered to show the shadow effect, and the shadow will be visible in the `light` mode:

```markdown
![Desktop View](/assets/img/sample/mockup.png){: .shadow }
```
{: .nolineno}

### CDN URL

If you host the images on the CDN, you can save the time of repeatedly writing the CDN URL by assigning the variable `img_cdn` of `_config.yml` file:

```yaml
img_cdn: https://cdn.com
```
{: file='_config.yml' .nolineno}

Once `img_cdn` is assigned, the CDN URL will be added to the path of all images (images of site avatar and posts) starting with `/`.

For instance, when using images:

```markdown
![The flower](/path/to/flower.png)
```
{: .nolineno}

The parsing result will automatically add the CDN prefix `https://cdn.com` before the image path:

```html
<img src="https://cdn.com/path/to/flower.png" alt="The flower">
```
{: .nolineno}

### Image path

When a post contains many images, it will be a time-consuming task to repeatedly define the path of the images. To solve this, we can define this path in the YAML block of the post:

```yml
---
img_path: /img/path/
---
```
{: .nolineno }

And then, the image source of Markdown can write the file name directly:

```md
![The flower](flower.png)
```
{: .nolineno }

The output will be:

```html
<img src="/img/path/flower.png" alt="The flower">
```
{: .nolineno }

## Pinned Posts

You can pin one or more posts to the top of the home page, and the fixed posts are sorted in reverse order according to their release date. Enable by:

```yaml
---
pin: true
---
```

## Code Block

Markdown symbols ```` ``` ```` can easily create a code block as follows:

```
This is a plaintext code snippet.
```

### Specifying Language

Using ```` ```{language} ```` you will get a code block with syntax highlight:

````markdown
```yaml
key: value
```
````

> **Limitation**: The Jekyll style `highlight` tag is not compatible with this theme.

### Line Number

By default, all languages except `plaintext`, `console`, and `terminal` will display line numbers. When you want to hide the line number of the code block, you can append `{: .nolineno}` at the next line:

````markdown
```shell
echo 'No more line numbers!'
```
{: .nolineno}
````

### Specifying the Filename

You may have noticed that the code language will be displayed on the left side of the header of the code block. If you want to replace it with the file name, you can add the attribute `file` to achieve this:

````markdown
```shell
# content
```
{: file="path/to/file" }
````

### Liquid Codes

If you want to display the **Liquid** snippet, surround the liquid code with `{% raw %}` and `{% endraw %}`:

````markdown
{% raw %}
```liquid
{% if product.title contains 'Pack' %}
  This product's title contains the word Pack.
{% endif %}
```
{% endraw %}
````

Or adding `render_with_liquid: false` (Requires Jekyll 4.0 or higher) to the post's YAML block.

## Learn More

For more knowledge about Jekyll posts, visit the [Jekyll Docs: Posts](https://jekyllrb.com/docs/posts/).