¿Cómo puedo limitar la longitud de los caracteres en un extracto?

agregueestas líneasen el archivofunction.php

 function custom_excerpt_length( $length ) {
        return 20;
    }
    add_filter( 'excerpt_length', 'custom_excerpt_length', 999 );
 

add these lines in function.php file

function custom_excerpt_length( $length ) {
        return 20;
    }
    add_filter( 'excerpt_length', 'custom_excerpt_length', 999 );

Además delgancho defiltro anteriorproporcionadopor la respuesta de Deepa,aquí hay unafunción adicional quepuede ayudarlo aextenderel uso de the_excerpt de dosmaneras,

Tepermite ...

Limiteelextractoporelnúmero de caracterespero NOtrunque la últimapalabra. Esto lepermitirá devolver unnúmeromáximo de caracteres,pero conservará laspalabras completas,por lo que solo se devolverán laspalabras quepueden caber dentro del límite denúmeroespecificado y lepermitiráespecificar lafuente de donde vendráelextracto.

 function get_excerpt($limit, $source = null){

    $excerpt = $source == "content" ? get_the_content() : get_the_excerpt();
    $excerpt = preg_replace(" (\[.*?\])",'',$excerpt);
    $excerpt = strip_shortcodes($excerpt);
    $excerpt = strip_tags($excerpt);
    $excerpt = substr($excerpt, 0, $limit);
    $excerpt = substr($excerpt, 0, strripos($excerpt, " "));
    $excerpt = trim(preg_replace( '/\s+/', ' ', $excerpt));
    $excerpt = $excerpt.'... <a href="'.get_permalink($post->ID).'">more</a>';
    return $excerpt;
}

/*
Sample...  Lorem ipsum habitant morbi (26 characters total) 

Returns first three words which is exactly 21 characters including spaces
Example..  echo get_excerpt(21);  
Result...  Lorem ipsum habitant 

Returns same as above, not enough characters in limit to return last word
Example..  echo get_excerpt(24);    
Result...  Lorem ipsum habitant  

Returns all 26 chars of our content, 30 char limit given, only 26 characters needed. 
Example..  echo get_excerpt(30);    
Result...  Lorem ipsum habitant morbi
*/
 

Estafunción sepuede utilizar varias vecesen los archivos detema,cada uno con diferentes límites de caracteresespecificados.

Estafuncióntiene la capacidad de recuperar unextracto de

• the_content
• the_excerpt

Porejemplo,sitiene publicaciones que contienentextoen el cuadro_excerpten lapantalla deleditor depublicaciones,pero deseaextraer unextracto del cuerpo del_contenten su lugarpara un caso de usoespecial que lo haría;

 get_excerpt(140, 'the_content'); //excerpt is grabbed from get_the_content
 

Esto le dice a lafunción que desea losprimeros 140 caracteres de the_content,independientemente de si unextractoestá configuradoen el cuadro the_excerpt.

 get_excerpt(140); //excerpt is grabbed from get_the_excerpt
 

Esto le dice a lafunción que desea losprimeros 140 caracteres de the_excerptprimero y sinoexisteningúnextracto,the_content se usará como respaldo.

Lafunciónpuedemejorarsepara que seamáseficiente oincorporarse conel uso defiltros de WordPresstantopara the_content o the_excerpt o simplemente usarsetal cualen situaciones donde noes una alternativa adecuada a la API de WordPressincorporada.

In addition to the above filter hook supplied by Deepa's answer here is one additional function that can help you extend the use of the_excerpt in two ways,

Allows you to...

Limit the excerpt by number of characters but do NOT truncate the last word. This will allow you to return a maximum number of characters but preserve full words, so only the words that can fit within the specified number limit are returned and allow you to specify the source of where the excerpt will come from.

function get_excerpt($limit, $source = null){

    $excerpt = $source == "content" ? get_the_content() : get_the_excerpt();
    $excerpt = preg_replace(" (\[.*?\])",'',$excerpt);
    $excerpt = strip_shortcodes($excerpt);
    $excerpt = strip_tags($excerpt);
    $excerpt = substr($excerpt, 0, $limit);
    $excerpt = substr($excerpt, 0, strripos($excerpt, " "));
    $excerpt = trim(preg_replace( '/\s+/', ' ', $excerpt));
    $excerpt = $excerpt.'... <a href="'.get_permalink($post->ID).'">more</a>';
    return $excerpt;
}

/*
Sample...  Lorem ipsum habitant morbi (26 characters total) 

Returns first three words which is exactly 21 characters including spaces
Example..  echo get_excerpt(21);  
Result...  Lorem ipsum habitant 

Returns same as above, not enough characters in limit to return last word
Example..  echo get_excerpt(24);    
Result...  Lorem ipsum habitant  

Returns all 26 chars of our content, 30 char limit given, only 26 characters needed. 
Example..  echo get_excerpt(30);    
Result...  Lorem ipsum habitant morbi
*/

This function can be used multiple times through out theme files, each with different character limits specified.

This function has the ability to retrieve an excerpt from either,

• the_content
• the_excerpt

For example, if you have posts that contain text in the_excerpt box on the post editor screen, but want to pull an excerpt from the_content body instead for a special use case you would instead do;

get_excerpt(140, 'the_content'); //excerpt is grabbed from get_the_content

This tells the function that you want the first 140 characters from the_content, regardless of whether an excerpt is set in the_excerpt box.

get_excerpt(140); //excerpt is grabbed from get_the_excerpt

This tells the function that you want the first 140 characters from the_excerpt first and if no excerpt exists, the_content will be used as a fallback.

The function can be improved to be made more efficient and or incorporated with the use of WordPress filters for both the_content or the_excerpt or simply used as is in situations where there is no suitable, in-built WordPress API alternative.