nginx access log 默认空字段为 -

Question

第一种情况，空的字段为“-”，是我想要的，只要不是“”就行，但是resp_body的双引号变成x22

# log_format
log_format  main  '"$remote_addr" "$remote_user" "$time_local" "$request" '
                      '"$status" "$body_bytes_sent" "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for" "$request_time" '
                      '"$request_body" "$resp_body"';
                      
#输出 
"127.0.0.1" "-" "16/Jan/2019:11:24:05 +0800" "POST /test HTTP/1.1" "200" "20" "-" "curl/7.47.0" "-" "0.001" "-" "{\x22data\x22: \x22asasddsf\x22}"

第二种情况,resp_body没问题，但空字段是“”，我想要有默认值

# log_format
log_format  main escape=none '"$remote_addr" "$remote_user" "$time_local" "$request" '
                      '"$status" "$body_bytes_sent" "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for" "$request_time" '
                      '"$request_body" "$resp_body"';
#输出
"127.0.0.1" "" "16/Jan/2019:11:47:07 +0800" "POST /test HTTP/1.1" "200" "20" "" "curl/7.47.0" "" "0.002" "" "{"data": "asasddsf"}"

能不能在第一种情况下把引号输出正常，或第二种情况下把空字段输出默认值，如默认值为-，输出”-“

Answer 1

把源码src/http/modules/ngx_http_log_module.c修改了下当escape=none时空值返回-，重新编译了一下。但是感觉应该有更好当办法。

ngx_http_log_unescaped_variable(ngx_http_request_t *r, u_char *buf,
    ngx_http_log_op_t *op)
{
    ngx_http_variable_value_t  *value;

    value = ngx_http_get_indexed_variable(r, op->data);

    if (value == NULL || value->not_found) {
        # 为空时返回-
        *buf = '-';
        return buf + 1;
    }

    return ngx_cpymem(buf, value->data, value->len);
}