[root@arbiter nginx]# /usr/local/nginx/sbin/nginx -t -c /usr/local/nginx/conf/nginx.conf
nginx: the configuration file /usr/local/nginx/conf/nginx.conf syntax is ok
nginx: configuration file /usr/local/nginx/conf/nginx.conf test is successful
[root@arbiter nginx]# echo $?
0

[root@arbiter nginx]# /usr/local/nginx/sbin/nginx -t -c /usr/local/nginx/conf/mime.types
nginx: [emerg] "types" directive is not allowed here in /usr/local/nginx/conf/mime.types:2
nginx: configuration file /usr/local/nginx/conf/mime.types test failed
[root@arbiter nginx]# echo $?
1

Dalam bash, $? digunakan untuk mendapatkan nilai pulangan bagi perintah sebelumnya 0 adalah normal, dan nilai lain tidak normal. $? 用来获取上一条命令的返回值，0 为正常，其他值为异常。

如果需要获取命令输出，可以按一下方式操作：

[root@arbiter nginx]# a="`/usr/local/nginx/sbin/nginx -t -c /usr/local/nginx/conf/mime.types 2>&1`"
[root@arbiter nginx]# echo $a
nginx: [emerg] "types" directive is not allowed here in /usr/local/nginx/conf/mime.types:2 nginx: configuration file /usr/local/nginx/conf/mime.types test failed

其中2>&1