Enable post excerpts in wordpress theme twentythirteen

In TwentyThirteen, there are many files, their names're started with content:

1. content.php
2. content-none.php
3. content-aside.php
4. content-audio.php
5. content-chat.php
6. content-gallery.php
7. content-image.php
8. content-link.php
9. content-quote.php
10. content-status.php
11. content-video.php

Among them, except the first two, all the others are for different post types, and you can understand their usages from their names.

The 2nd one, content-none.php is used to display apology texts, when there is no content found with a query. And the 1st one, content.php is used in various display pages with two conditions, where:

• is_search() — is to check whether it is the search result page
• is_single() — is to check whether it is the post details page

If you open the index.php, you will find a code:

<?php get_template_part( 'content', get_post_format() ); ?>

Here the template part (content.php) is called.

Answer

So, to show excerpt in your front page or home page, you will need to modify content.php. Like the is_search(), is_single(), there are several other checkers in WordPress:

• is_home() — is to check whether it is the home page
• is_front_page() — is to check whether it is the front-page
• is_category() — is to check whether it is the category archive page
• is_archive() — is to check whether it is the general archive page
• is_tag() — is to check whether it is the tags archive page
• ...so on

And you may know that, to enable excerpt instead of full content, you will have to change the code the_content() to the_excerpt().

More Details

• get_template_part()
• the_excerpt()
• the_content()

EDIT

Yep, @Rarst said a very important thing that, if you make change into any public theme, the changes will be wiped out when a new update will take place. So, to put your modifications in place, you have to make a Child Theme on TwentyThirteen. A Child Theme is nothing but a new folder with a stylesheet. You can get that at:

• Child Themes - WordPress Codex