$ sudo nginx -t
nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful

[root@d ~]# /usr/local/nginx/sbin/nginx -t;echo $?
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
0
[root@d ~]# echo whatever > /usr/local/nginx/nonsense.conf
[root@d ~]# /usr/local/nginx/sbin/nginx -t -c nonsense.conf;echo $?
nginx: [emerg] unexpected end of file, expecting ";" or "}" in /usr/local/nginx/nonsense.conf:2
nginx: configuration file /usr/local/nginx/nonsense.conf test failed
1

#!/bin/bash
/usr/local/nginx/sbin/nginx -t 2>/dev/null > /dev/null
if [[ $? == 0 ]]; then
 echo "success"
 # do things on success
else
 echo "fail"
 # do whatever on fail
fi