Provided by: nginx-confgen_2.1-1_amd64 
NAME
nginx-confgen - A preprocessor and macro system for nginx(-like) configuration files.
SYNOPSIS
nginx-confgen -i input.conf -o output.conf
DESCRIPTION
nginx-confgen can be used to do pre-processing for nginx configuration files (and other
configuration files with a similar syntax). It has support for "compile-time" macro
expansion and variable interpolation, which should make it less tedious to maintain large
and complex configurations.
nginx-confgen works by parsing the input into a syntax tree, modifying this tree, and then
formatting the tree to generate the output. It is completely oblivious to nginx contexts
and directives, so it is possible to do nonsensical transformations and generate incorrect
configuration files. Comments in the input file will not be present in the output. See
also the "BUGS & WARTS" below.
SECURITY CONSIDERATION: Do NOT use nginx-confgen with untrusted input, the "pre_exec"
directive allows arbitrary code execution by design.
OPTIONS
The following command-line options are supported:
-h Show help text.
-V, --version
Show program version.
-i FILE
Use the given file name as input file. If this option is not given or set to "-", then
the file will be read from standard input.
-o FILE
Write the output to the given file. If this option is not given or set to "-", then
the file will be written to standard output.
-I DIR
Set the search path for pre_include directives. This option can be given multiple
times to search several directories in order. If this option is not given, then
include files are resolved relative to the directory that nginx-confgen is run from
(i.e. "-I .").
DIRECTIVES
nginx-confgen recognizes and interprets the following directives:
pre_include
Similar to the "include" directive in nginx, except that the file is included during
preprocessing. The included file may contain any preprocessing directives supported by
nginx-confgen. Variables and macros defined in the included file will be available in the
parent file.
Relative paths are searched for in the directories given with the "-I" flag.
pre_set
Similar to the "set" directive in nginx, except that variables defined with "pre_set" are
resolved during preprocessing. Variables are set in the order that they are encountered in
the configuration file, regardless of scoping. For example:
pre_set $var outer;
location / {
pre_set $var inner;
}
# $var is "inner" at this point.
Only variables that are known to nginx-confgen will be substituted, unknown variables are
assumed to be run-time variables for nginx and will be left alone without warning. For
example:
pre_set $ip 127.0.0.1;
deny $ip; # This will output as: deny 127.0.0.1;
deny $otherip; # This will output as: deny $otherip;
pre_exec
Run a shell command and store the output in a variable. For example, nginx will not use
your system's DNS resolution methods to resolve domain names, instead you need to manually
set a "resolver" address. With the following hack you can fetch the nameserver from
"/etc/resolv.conf" and use that as the "resolver":
pre_exec $nameserver "grep nameserver /etc/resolv.conf \\
| head -n 1 | sed 's/^nameserver //'";
resolver $nameserver;
(The "\\" is necessary, otherwise your shell will consider the newline as a new command).
pre_if
Similar to the "if" directive in nginx, except that this is evaluated during
preprocessing. Braces around the condition are optional. Some examples:
pre_if -f $certdir/ocsp.der {
ssl_stapling on;
ssl_stapling_file $certdir/ocsp.der;
}
pre_if (!-f $certdir/ocsp.der) {
ssl_stapling off;
}
# You can have different configuration depending on the name of
# the system on which nginx-confgen runs. Like... yeah.
pre_exec $hostname 'hostname';
pre_if $hostname ~* ^proxy_for_(.+) {
proxy_pass http://$1/;
}
pre_warn
This directive, when interpreted, will generate a warning to the standard error of nginx-
confgen. Can be used to signal that a special configuration is being used:
pre_if -e /etc/offline-mode {
pre_warn "Putting website in offline mode!";
}
Or to warn about certain directives:
pre_macro proxy_cache $var {
pre_warn "Using proxy_cache with $var violates company policy!";
# But we can output it anyway.
proxy_cache $var;
}
macro
Define a macro, which is a configuration block that you can later refer to. The general
syntax is as follows:
macro macro_name $var1 $var2 @remaining_vars &block_var {
# contents
}
The optional @remaining_vars argument will capture any number of variables and can be
passed to another directive inside the macro contents. The optional &block_var allows the
macro to be invoked with a block argument, which will expand to any number of directives.
Some examples:
macro le {
location /.well-known/acme-challenge {
alias /etc/letsencrypt/challenge;
}
}
# Usage:
le;
macro redir $path $to {
location $path {
return 301 $to;
}
}
# Usage:
redir / http://blicky.net/;
macro vhost $primary_name @aliases &block {
server {
listen [::]:443 ssl;
server_name $primary_name @aliases;
ssl_certificate $crtdir/$primary_name/fullchain.pem;
ssl_certificate_key $crtdir/$primary_name/privkey.pem;
█
}
}
# Usage:
vhost example.com {
root /var/www/example.com;
}
vhost example.org alias.example.org {
root /var/www/example.org;
}
Note that these are hygienic macros, so variable capture is predictable (but not
necessarily the most useful):
pre_var $dest /a;
macro redir {
# This will be /a, regardless of the context in which this macro is called.
return 301 $dest;
}
# $dest is still '/a' inside the macro after this new variable definition.
pre_var $dest /b;
redir;
Similarly, macro arguments will not be available inside &block expansion or nested macro
expansion and any variables set inside a macro will not be available outside of the macro
body.
BUGS & WARTS
nginx-confgen is a quickly written hack to solve a particular use case, it is quite likely
to have some weird behavior and bugs. In particular, processing performance may suffer on
large configuration files with many macros and/or variables. Performance has simply not
been a problem for me, but if you do run into trouble with your use case, let me know so I
can fix it.
Comments and whitespace in the input files are thrown away and ignored. The generated
output is completely reformatted.
The nginx configuration syntax is not as regular as I had hoped. It's possible for nginx
modules to extend the syntax somewhat. A good example is the types directive in
ngx_http_core_module. While nginx-confgen should be able to handle the types directive
just fine, other extensions may cause syntax errors or will not survive a round-trip
through nginx-confgen. This applies to all *_by_lua_block directives in the
ngx_http_lua_module. The _by_lua directives that accept a string should work just fine.
AUTHOR
nginx-confgen is written by Yoran Heling <projects@yorhel.nl>
Web: <https://dev.yorhel.nl/nginx-confgen>