WordPress at a glance
function is not described

wp_set_link_cats() WP 2.1.0

Update link with the specified link categories.

No Hooks.

Return

Nothing (null).

Usage

wp_set_link_cats( $link_id, $link_categories );
$link_id(int)
ID of the link to update.
Default: 0
$link_categories(int[])
Array of link category IDs to add the link to.
Default: array()

Code of wp set link cats: wp-admin/includes/bookmark.php VER 5.1.1

<?php
function wp_set_link_cats( $link_id = 0, $link_categories = array() ) {
	// If $link_categories isn't already an array, make it one:
	if ( ! is_array( $link_categories ) || 0 == count( $link_categories ) ) {
		$link_categories = array( get_option( 'default_link_category' ) );
	}

	$link_categories = array_map( 'intval', $link_categories );
	$link_categories = array_unique( $link_categories );

	wp_set_object_terms( $link_id, $link_categories, 'link_category' );

	clean_bookmark_cache( $link_id );
}