location = / { 
 # matches the query / only. 
 [ configuration A ]  
} 
location / { 
 # matches any query, since all queries begin with /, but regular 
 # expressions and any longer conventional blocks will be 
 # matched first. 
 [ configuration B ]  
} 
location ^~ /images/ { 
 # matches any query beginning with /images/ and halts searching, 
 # so regular expressions will not be checked. 
 [ configuration C ]  
} 
location ~* \.(gif|jpg|jpeg)$ { 
 # matches any request ending in gif, jpg, or jpeg. However, all 
 # requests to the /images/ directory will be handled by 
 # Configuration C.   
 [ configuration D ]  
} 
 
location @named { 
 # Such locations are not used during normal processing of requests,  
 # they are intended only to process internally redirected requests (for example error_page, try_files). 
 [ configuration E ]  
} 

ngx_http_location_tree_node_t  *static_locations; 
(NGX_PCRE) 
ngx_http_core_loc_conf_t    **regex_locations; 
if 

location tree和regex_locations数组建立过程在ngx_http_block中：
/* create location trees */ 
 
  for (s = 0; s < cmcf->servers.nelts; s++) { 
 
    clcf = cscfp[s]->ctx->loc_conf[ngx_http_core_module.ctx_index]; 
 
    if (ngx_http_init_locations(cf, cscfp[s], clcf) != NGX_OK) { 
      return NGX_CONF_ERROR; 
    } 
 
    if (ngx_http_init_static_location_trees(cf, clcf) != NGX_OK) { 
      return NGX_CONF_ERROR; 
    } 
  } 

static ngx_int_t 
ngx_http_init_locations(ngx_conf_t *cf, ngx_http_core_srv_conf_t *cscf, 
  ngx_http_core_loc_conf_t *pclcf) 
{ 
 ... 
  locations = pclcf->locations; 
 
 ... 
  /* 按照类型排序location，排序完后的队列： (exact_match 或 inclusive) (排序好的，如果某个exact_match名字和inclusive location相同，exact_match排在前面) 
    | regex（未排序）| named(排序好的) | noname（未排序）*/ 
  ngx_queue_sort(locations, ngx_http_cmp_locations); 
 
  named = NULL; 
  n = 0; 
#if (NGX_PCRE) 
  regex = NULL; 
  r = 0; 
#endif 
 
  for (q = ngx_queue_head(locations); 
     q != ngx_queue_sentinel(locations); 
     q = ngx_queue_next(q)) 
  { 
    lq = (ngx_http_location_queue_t *) q; 
 
    clcf = lq->exact ? lq->exact : lq->inclusive; 
    /* 由于可能存在nested location，也就是location里面嵌套的location，这里需要递归的处理一下当前location下面的nested location */ 
    if (ngx_http_init_locations(cf, NULL, clcf) != NGX_OK) { 
      return NGX_ERROR; 
    } 
 
#if (NGX_PCRE) 
 
    if (clcf->regex) { 
      r++; 
 
      if (regex == NULL) { 
        regex = q; 
      } 
 
      continue; 
    } 
 
#endif 
 
    if (clcf->named) { 
      n++; 
 
      if (named == NULL) { 
        named = q; 
      } 
 
      continue; 
    } 
 
    if (clcf->noname) { 
      break; 
    } 
  } 
 
  if (q != ngx_queue_sentinel(locations)) { 
    ngx_queue_split(locations, q, &tail); 
  } 
  /* 如果有named location，将它们保存在所属server的named_locations数组中 */ 
  if (named) { 
    clcfp = ngx_palloc(cf->pool, 
              (n + 1) * sizeof(ngx_http_core_loc_conf_t **)); 
    if (clcfp == NULL) { 
      return NGX_ERROR; 
    } 
 
    cscf->named_locations = clcfp; 
 
    for (q = named; 
       q != ngx_queue_sentinel(locations); 
       q = ngx_queue_next(q)) 
    { 
      lq = (ngx_http_location_queue_t *) q; 
 
      *(clcfp++) = lq->exact; 
    } 
 
    *clcfp = NULL; 
 
    ngx_queue_split(locations, named, &tail); 
  } 
 
#if (NGX_PCRE) 
  /* 如果有正则匹配location，将它们保存在所属server的http core模块的loc配置的regex_locations 数组中， 
    这里和named location保存位置不同的原因是由于named location只能存在server里面，而regex location可以作为nested location */ 
  if (regex) { 
 
    clcfp = ngx_palloc(cf->pool, 
              (r + 1) * sizeof(ngx_http_core_loc_conf_t **)); 
    if (clcfp == NULL) { 
      return NGX_ERROR; 
    } 
 
    pclcf->regex_locations = clcfp; 
 
    for (q = regex; 
       q != ngx_queue_sentinel(locations); 
       q = ngx_queue_next(q)) 
    { 
      lq = (ngx_http_location_queue_t *) q; 
 
      *(clcfp++) = lq->exact; 
    } 
 
    *clcfp = NULL; 
 
    ngx_queue_split(locations, regex, &tail); 
  } 
 
#endif 
 
  return NGX_OK; 
} 

static ngx_int_t 
ngx_http_init_static_location_trees(ngx_conf_t *cf, 
  ngx_http_core_loc_conf_t *pclcf) 
{ 
  ngx_queue_t        *q, *locations; 
  ngx_http_core_loc_conf_t  *clcf; 
  ngx_http_location_queue_t *lq; 
 
  locations = pclcf->locations; 
 
  if (locations == NULL) { 
    return NGX_OK; 
  } 
 
  if (ngx_queue_empty(locations)) { 
    return NGX_OK; 
  } 
  /* 这里也是由于nested location，需要递归一下 */ 
  for (q = ngx_queue_head(locations); 
     q != ngx_queue_sentinel(locations); 
     q = ngx_queue_next(q)) 
  { 
    lq = (ngx_http_location_queue_t *) q; 
 
    clcf = lq->exact ? lq->exact : lq->inclusive; 
 
    if (ngx_http_init_static_location_trees(cf, clcf) != NGX_OK) { 
      return NGX_ERROR; 
    } 
  } 
  /* join队列中名字相同的inclusive和exact类型location，也就是如果某个exact_match的location名字和普通字符串匹配的location名字相同的话， 
    就将它们合到一个节点中，分别保存在节点的exact和inclusive下，这一步的目的实际是去重，为后面的建立排序树做准备 */ 
  if (ngx_http_join_exact_locations(cf, locations) != NGX_OK) { 
    return NGX_ERROR; 
  } 
  /* 递归每个location节点，得到当前节点的名字为其前缀的location的列表，保存在当前节点的list字段下 */ 
  ngx_http_create_locations_list(locations, ngx_queue_head(locations)); 
 
  /* 递归建立location三叉排序树 */ 
  pclcf->static_locations = ngx_http_create_locations_tree(cf, locations, 0); 
  if (pclcf->static_locations == NULL) { 
    return NGX_ERROR; 
  } 
 
  return NGX_OK; 
} 

location /xyz { 
 
} 
 
location = /xyz { 
 
} 
location /xyza { 
 
} 
 
location /xyzab { 
 
} 
location /xyzb { 
 
} 
location /abc { 
 
} 
location /efg { 
 
} 
location /efgaa { 
 
} 

static ngx_http_location_tree_node_t * 
ngx_http_create_locations_tree(ngx_conf_t *cf, ngx_queue_t *locations, 
  size_t prefix) 
{ 
  ... 
  /* 根节点为locations队列的中间节点 */ 
  q = ngx_queue_middle(locations); 
 
  lq = (ngx_http_location_queue_t *) q; 
  len = lq->name->len - prefix; 
   
  node = ngx_palloc(cf->pool, 
           offsetof(ngx_http_location_tree_node_t, name) + len); 
  if (node == NULL) { 
    return NULL; 
  } 
 
  node->left = NULL; 
  node->right = NULL; 
  node->tree = NULL; 
  node->exact = lq->exact; 
  node->inclusive = lq->inclusive; 
 
  node->auto_redirect = (u_char) ((lq->exact && lq->exact->auto_redirect) 
              || (lq->inclusive && lq->inclusive->auto_redirect)); 
 
  node->len = (u_char) len; 
  ngx_memcpy(node->name, &lq->name->data[prefix], len); 
 
  /* 从中间节点开始断开 */ 
  ngx_queue_split(locations, q, &tail); 
 
  if (ngx_queue_empty(locations)) { 
    /* 
     * ngx_queue_split() insures that if left part is empty, 
     * then right one is empty too 
     */ 
    goto inclusive; 
  } 
 
  /* 从locations左半部分得到左子树 */ 
  node->left = ngx_http_create_locations_tree(cf, locations, prefix); 
  if (node->left == NULL) { 
    return NULL; 
  } 
 
  ngx_queue_remove(q); 
 
  if (ngx_queue_empty(&tail)) { 
    goto inclusive; 
  } 
  
 
  /* 从locations右半部分得到右子树 */ 
  node->right = ngx_http_create_locations_tree(cf, &tail, prefix); 
  if (node->right == NULL) { 
    return NULL; 
  } 
 
inclusive: 
 
  if (ngx_queue_empty(&lq->list)) { 
    return node; 
  } 
 
  /* 从list队列得到tree子树 */ 
  node->tree = ngx_http_create_locations_tree(cf, &lq->list, prefix + len); 
  if (node->tree == NULL) { 
    return NULL; 
  } 
 
  return node; 
} 
     location tree节点的ngx_http_location_tree_node_s结构：
struct ngx_http_location_tree_node_s { 
  ngx_http_location_tree_node_t  *left; 
  ngx_http_location_tree_node_t  *right; 
  ngx_http_location_tree_node_t  *tree; 
 
  ngx_http_core_loc_conf_t    *exact; 
  ngx_http_core_loc_conf_t    *inclusive; 
 
  u_char              auto_redirect; 
  u_char              len; 
  u_char              name[1]; 
}; 

Example:
server {
  server_name jb51.net;
  location = /abcd {
  […]
  }
}

  http://jb51.net/abcd    # 正好完全匹配
  http://jb51.net/ABCD    # 如果运行 Nginx server 的系统本身对大小写不敏感，比如 Windows ，那么也匹配
  http://jb51.net/abcd?param1¶m2  # 忽略查询串参数（query string arguments），这里就是 /abcd 后面的 ?param1¶m2
  http://jb51.net/abcd/  # 不匹配，因为末尾存在反斜杠（trailing slash），Nginx 不认为这种情况是完全匹配
  http://jb51.net/abcde  # 不匹配，因为不是完全匹配

Example:
server {
  server_name jb51.net;
  location /abcd {
  […]
  }
}

  http://jb51.net/abcd    # 正好完全匹配
  http://jb51.net/ABCD    # 如果运行 Nginx server 的系统本身对大小写不敏感，比如 Windows ，那么也匹配
  http://jb51.net/abcd?param1¶m2  # 忽略查询串参数（query string arguments），这里就是 /abcd 后面的 ?param1¶m2
  http://jb51.net/abcd/  # 末尾存在反斜杠（trailing slash）也属于匹配范围内
  http://jb51.net/abcde  # 仍然匹配，因为 URI 是以 pattern 开头的

Example:
server {
  server_name jb51.net;
  location ~ ^/abcd$ {
  […]
  }
}

  http://jb51.net/abcd    # 完全匹配
  http://jb51.net/ABCD    # 不匹配，~ 对大小写是敏感的
  http://jb51.net/abcd?param1¶m2  # 忽略查询串参数（query string arguments），这里就是 /abcd 后面的 ?param1¶m2
  http://jb51.net/abcd/  # 不匹配，因为末尾存在反斜杠（trailing slash），并不匹配正则表达式 ^/abcd$
  http://jb51.net/abcde  # 不匹配正则表达式 ^/abcd$

Example:
server {
  server_name jb51.net;
  location ~* ^/abcd$ {
  […]
  }
}

 http://jb51.net/abcd    # 完全匹配
  http://jb51.net/ABCD    # 匹配，这就是它不区分大小写的特性
  http://jb51.net/abcd?param1¶m2  # 忽略查询串参数（query string arguments），这里就是 /abcd 后面的 ?param1¶m2
  http://jb51.net/abcd/  # 不匹配，因为末尾存在反斜杠（trailing slash），并不匹配正则表达式 ^/abcd$
  http://jb51.net/abcde  # 不匹配正则表达式 ^/abcd$