Solution 1:

It seems that your nginx hasn't been installed correctly. Pay attention to the output of the installation commands:

sudo apt-get install nginx

To check the nginx version, you can use this command:

$ nginx -v
nginx version: nginx/0.8.54

$ nginx -V
nginx version: nginx/0.8.54
TLS SNI support enabled
configure arguments: --conf-path=/etc/nginx/nginx.conf --error-log-path=/var/log/nginx/error.log --http-client-body-temp-path=/var/lib/nginx/body --http-fastcgi-temp-path=/var/lib/nginx/fastcgi --http-log-path=/var/log/nginx/access.log --http-proxy-temp-path=/var/lib/nginx/proxy --http-scgi-temp-path=/var/lib/nginx/scgi --http-uwsgi-temp-path=/var/lib/nginx/uwsgi --lock-path=/var/lock/nginx.lock --pid-path=/var/run/nginx.pid --with-debug --with-http_addition_module --with-http_dav_module --with-http_geoip_module --with-http_gzip_static_module --with-http_image_filter_module --with-http_realip_module --with-http_stub_status_module --with-http_ssl_module --with-http_sub_module --with-http_xslt_module --with-ipv6 --with-sha1=/usr/include/openssl --with-md5=/usr/include/openssl --with-mail --with-mail_ssl_module --add-module=/build/buildd/nginx-0.8.54/debian/modules/nginx-upstream-fair

For more information: http://nginxlibrary.com/check-nginx-version/

You can use -v parameter to display the Nginx version only, or use the -V parameter to display the version, along with the compiler version and configuration parameters.

Solution 2:

In my case, I try to add sudo

sudo nginx -v

enter image description here

Solution 3:

If you don't know where it is, locate nginx first.

ps -ef | grep nginx

Then you will see something like this:

root      4801     1  0 May23 ?        00:00:00 nginx: master process /opt/nginx/sbin/nginx -c /opt/nginx/conf/nginx.conf
root     12427 11747  0 03:53 pts/1    00:00:00 grep --color=auto nginx
nginx    24012  4801  0 02:30 ?        00:00:00 nginx: worker process                              
nginx    24013  4801  0 02:30 ?        00:00:00 nginx: worker process

So now you already know where nginx is. You can use the -v or -V. Something like:

/opt/nginx/sbin/nginx -v

Solution 4:

My guess is it's not in your path.
in bash, try:
echo $PATH
and
sudo which nginx
And see if the folder containing nginx is also in your $PATH variable.
If not, either add the folder to your path environment variable, or create an alias (and put it in your .bashrc) ooor your could create a link i guess.
or sudo nginx -v if you just want that...

Solution 5:

Make sure that you have permissions to run the following commands.

If you check the man page of nginx from a terminal

man nginx

you can find this:

-V             Print the nginx version, compiler version, and configure script parameters.

-v             Print the nginx version.

Then type in terminal

nginx -v
nginx version: nginx/1.14.0

nginx -V
nginx version: nginx/1.14.0
built with OpenSSL 1.1.0g  2 Nov 2017
TLS SNI support enabled

If nginx is not installed in your system man nginx command can not find man page, so make sure you have installed nginx.

You can also find the version using this command:

Use one of the command to find the path of nginx

ps aux | grep nginx
ps -ef | grep nginx

root       883  0.0  0.3  44524  3388 ?        Ss   Dec07   0:00 nginx: master process /usr/sbin/nginx -g daemon on; master_process on

Then run from terminal:

/usr/sbin/nginx -v

nginx version: nginx/1.14.0