Nginx language specification file for GtkSourceView.

nginx.lang

<?xml version="1.0" encoding="UTF-8"?>
<language id="nginx" _name="Nginx conf file" version="2.0" _section="Other">
  <metadata>
    <property name="mimetypes">text/x-nginx-conf-file;application/x-nginx-conf-file</property>
    <property name="globs">*.conf</property>
    <property name="line-comment-start">#</property>
  </metadata>

  <styles>
    <style id="comment" _name="Comment" map-to="def:comment"/>
    <style id="string" _name="String" map-to="def:string"/>
    <style id="name" _name="Keyword" map-to="def:keyword"/>
    <style id="variable" _name="Variable" map-to="def:type"/>
    <style id="special-char"  _name="Escaped Character" map-to="def:special-char"/>
    <style id="decimal" _name="Decimal" map-to="def:decimal"/>
    <style id="float" _name="Floating point number" map-to="def:floating-point"/>
    <style id="boolean" _name="Boolean Value" map-to="def:boolean"/>
  </styles>

  <definitions>
    <context id="line-comment" style-ref="comment" end-at-line-end="true" class="comment" class-disabled="no-spell-check">
      <start>#</start>
    </context>
    
    <context id="block" end-parent="true" once-only="true" extend-parent="true">
      <start>\{</start>
      <end>\}</end>
      <include>
        <context ref="line-comment"/>
        <context ref="directive"/>
      </include>
    </context>
    
    <context id="variable" style-ref="variable">
      <match>\$\{?\w+\}?</match>
    </context>
    
    <context id="string_dbl" style-ref="string" end-at-line-end="true" class="string" class-disabled="no-spell-check">
      <start>"</start>
      <end>"</end>
      <include>
        <context id="double_escape" style-ref="special-char">
          <match>\\(?:"|$)</match>
        </context>
        <context ref="variable" />
      </include>
    </context>
    
    <context id="string" style-ref="string" end-at-line-end="true" class="string" class-disabled="no-spell-check">
      <start>'</start>
      <end>'</end>
      <include>
        <context id="single_escape" style-ref="special-char">
          <match>\\(?:'|\$)</match>
        </context>
        <context ref="variable" />
      </include>
    </context>
    
    <context id="decimal" style-ref="decimal">
      <match>-?(?:[1-9][0-9]*|0)(?![.eE])(?=\s|;|$)</match>
    </context>

    <context id="float" style-ref="float">
      <match>-?(?:[1-9][0-9]*|0)(?:\.[0-9]+)?(?:[eE][+\-]?[0-9]+)?(?=\s|;|$)</match>
    </context>
    
    <context id="boolean" style-ref="boolean">
      <match>(?:on|off|true|false)</match>
    </context>
    
    <context id="value" class="string" class-disabled="no-spell-check">
      <match>[^\s;{}"']+</match>
    </context>

    <context id="parameters">
      <include>
        <context ref="line-comment"/>
        <context ref="float" />
        <context ref="decimal" />
        <context ref="boolean" />
        <context ref="variable" />
        <context ref="value"/>
        <context ref="string_dbl"/>
        <context ref="string"/>
        <context ref="block"/>
      </include>
    </context>
    
    <context id="directive">
      <start>[\w./-]+</start>
      <end>;</end>
      <include>
        <context sub-pattern="0" style-ref="name" where="start"/>
        <context ref="parameters" />
      </include>
    </context>
    
    <context id="nginx" class="no-spell-check">
      <include>
        <context ref="line-comment"/>
        <context ref="directive"/>
      </include>
    </context>
    
  </definitions>
</language>

Put this file into /usr/local/share/gtksourceview-3.0/language-specs (or 2.0, it should work with that as well) for everyone, or ~/.local/share/gtksourceview-3.0/language-specs for only your user, and all applications using GtkSourceView (e.g. gedit) will have syntax highlight for Nginx conf files.