if的逻辑用法

什么是逻辑用法呢, 就程序中的and、or关系, 就叫做逻辑了.

NGINX支持if的 and 与 or 或者 && 与 || 吗？

答案是No. 当你尝试这样配置, 重载nginx时, nginx会报出错误

location = /test/ {
    default_type text/html;
    set $b 0;
    if ( $remote_addr != '' && $http_x_forwarded_for != '' ){
        set $b '1';
    }
    echo $b;
}

[root@test-vm ~]# /usr/local/nginx/sbin/nginx -t

nginx: [emerg] invalid condition "$remote_addr" in /usr/local/nginx/conf/nginx.conf:60 configuration file /usr/local/nginx/conf/nginx.conf test failed 那么我们应该怎样来实现and 和or的逻辑关系呢？

location = /test_and/ {
    default_type text/html;
    set $a 0;
    set $b 0;
    if ( $remote_addr != '' ){
        set $a 1;
    }
    if ( $http_x_forwarded_for != '' ){
        set $a 1$a;
    }
    if ( $a = 11 ){
        set $b 1;
    }
    echo $b;
}
location = /test_or/ {
    default_type text/html;
    set $a 0;
    set $b 0;
    if ( $remote_addr != '' ){
        set $a 1;
    }
    if ( $http_x_forwarded_for != '' ){
        set $a 1;
    }
    if ( $a = 1 ){
        set $b 1;
    }
    echo $b;
}