sed delete code block from file - regex

Question

I want to remove the server {...} code block from the default nginx configuration server configuration file.
sudo sed -i '/(\s*#?)server \s*{(?:[\s\S]+)\1}/ d' /opt/nginx/conf/nginx.conf
produces sed: -e expression #1, char 33: Invalid back reference
However using tools like Rubular the match works just fine. Essentially what I need to do is match the code block based on matched indentation otherwise too much will be deleted.
You can test this yourself in Rubular using the default nginx config as a test string:
#user nobody;
#Defines which Linux system user will own and run the Nginx server
worker_processes 1;
#Referes to single threaded process. Generally set to be equal to the number of CPUs or cores.
#error_log logs/error.log; #error_log logs/error.log notice;
#Specifies the file where server logs.
#pid logs/nginx.pid;
#nginx will write its master process ID(PID).
events {
worker_connections 1024;
# worker_processes and worker_connections allows you to calculate maxclients value:
# max_clients = worker_processes * worker_connections
}
http {
include mime.types;
# anything written in /opt/nginx/conf/mime.types is interpreted as if written inside the http { } block
default_type application/octet-stream;
#
#log_format main '$remote_addr - $remote_user [$time_local] "$request" '
# '$status $body_bytes_sent "$http_referer" '
# '"$http_user_agent" "$http_x_forwarded_for"';
#access_log logs/access.log main;
sendfile on;
# If serving locally stored static files, sendfile is essential to speed up the server,
# But if using as reverse proxy one can deactivate it
#tcp_nopush on;
# works opposite to tcp_nodelay. Instead of optimizing delays, it optimizes the amount of data sent at once.
#keepalive_timeout 0;
keepalive_timeout 65;
# timeout during which a keep-alive client connection will stay open.
#gzip on;
# tells the server to use on-the-fly gzip compression.
server {
# You would want to make a separate file with its own server block for each virtual domain
# on your server and then include them.
listen 80;
#tells Nginx the hostname and the TCP port where it should listen for HTTP connections.
# listen 80; is equivalent to listen *:80;
server_name localhost;
# lets you doname-based virtual hosting
#charset koi8-r;
#access_log logs/host.access.log main;
location / {
#The location setting lets you configure how nginx responds to requests for resources within the server.
root html;
index index.html index.htm;
}
#error_page 404 /404.html;
# redirect server error pages to the static page /50x.html
#
error_page 500 502 503 504 /50x.html;
location = /50x.html {
root html;
}
# proxy the PHP scripts to Apache listening on 127.0.0.1:80
#
#location ~ \.php$ {
# proxy_pass http://127.0.0.1;
#}
# pass the PHP scripts to FastCGI server listening on 127.0.0.1:9000
#
#location ~ \.php$ {
# root html;
# fastcgi_pass 127.0.0.1:9000;
# fastcgi_index index.php;
# fastcgi_param SCRIPT_FILENAME /scripts$fastcgi_script_name;
# include fastcgi_params;
#}
# deny access to .htaccess files, if Apache's document root
# concurs with nginx's one
#
#location ~ /\.ht {
# deny all;
#}
}
# another virtual host using mix of IP-, name-, and port-based configuration
#
#server {
# listen 8000;
# listen somename:8080;
# server_name somename alias another.alias;
# location / {
# root html;
# index index.html index.htm;
# }
#}
# HTTPS server
#
#server {
# listen 443 ssl;
# server_name localhost;
# ssl_certificate cert.pem;
# ssl_certificate_key cert.key;
# ssl_session_cache shared:SSL:1m;
# ssl_session_timeout 5m;
# ssl_ciphers HIGH:!aNULL:!MD5;
# ssl_prefer_server_ciphers on;
# location / {
# root html;
# index index.html index.htm;
# }
#}
}

Answer 1

sed doesn't allow regex to span multiple lines, so you would need to use multiple commands to achieve what you want, e.g. something like:
'/(\s*#?)server\s*\{/,/\1\}/d'
But unfortunately sed doesn't allow back references from previous regexes, so the above doesn't work.

Answer 2

A couple of things here.
First, by default, sed uses BRE as its regular expression format. You either need to write your regexes in BRE, or you need to use an option for sed that tells it to interpret ERE. The option will depend on your platform, which you haven't shared as a tag, so read your man page for sed to see what to use.
Second, in order to process text over multiple lines, you need to have those multiple lines in your edit buffer. You do this by appending them to your hold buffer as you step through the file, then processing them all at once. This is highly advanced sed usage, and more difficult than most people can deal with. Even if we can put together something that works, it will read like line noise and be virtually unsupportable after-the-fact.
I'd suggest using awk instead.
#!/usr/bin/awk -f
# pay attention to are "start of server" line,
/^[[:space:]]*server {/ { n=1 }
# increment bracket counter within the server block,
n>0 && /^[[:space:]]*{/ { n++ }
# decrement the bracket counter within the server block,
n>0 && /^[[:space:]]*}/ { n-- }
# and if we're still within the block, skip to the next line.
n>0 { next }
# short-hand for "print the current line"
1
Note that the conditions contain n>0 rather than just n because awk considers any non-zero value to evaluate to "true".
Note also that this will only work on files that contain a single squirly bracket per line. I'm not sure whether nginx requires this, but if it permits closing a section within a section using } }, beware that the script above will not parse that correctly.
YMMV. Not tested on animals. May contain nuts.