[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

bash, $? is used to get the return value of the previous command. 0 is normal, and other values ​​are abnormal.

If you need to get the command output, you can do it as follows:

[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

The function of 2>&1 is to redirect standard error to standard output