Following some help provided by Tobias, I am trying to assign a font-lock-keyword-face to all text (:alpha:) to the left of an equal sign (=) in a new Tecplot major mode. I read through the regexp section of elisp.pdf and came up with [^# ][[:alpha:]] =", but this only matches the first two letters to the left of the equal sign and the equal sign. In my code:

# To ensure all the data needed is displayed, activate the surfaces of          
# each zone, and extract from the auxilary data, the number of zones            
# in the data set. This number is used throughout this macro to control         
# various operations.                                                           

$!System "echo \" \" "

$!If "|AuxDataSet:SolverName|" == "OVERFLOW"

  $!FieldMap [1-|NumZones|]  Surfaces{SurfacesToPlot = BoundaryFaces}
  $!FieldMap [1-|NumZones|]  Surfaces{IRange{Max = 0}}
  $!FieldMap [1-|NumZones|]  Surfaces{JRange{Max = 0}}
  $!FieldMap [1-|NumZones|]  Surfaces{KRange{Max = 0}}


  $!FieldMap [1-|NumZones|]  Surfaces{SurfacesToPlot = BoundaryFaces}


the "ax =" and "ot =" are getting the font. However, I do not want to include the equal sign but I do want to include the entire word, such as "Max" and "SurfaceToPlot". How do I get just the word to the left of the equal sign.

  • Please show your font-lock code as well. To exclude the = you would group part of your regexp, and then tell font-lock to use that group of the matching text.
    – phils
    Apr 30, 2020 at 23:09

1 Answer 1


In trying to answer your problem, I ran into M-x regex-builder, which may help you as you try to build these regular expressions.

Anyways, you've only defined 4 characters to match:

  1. something that's not a # or space
  2. something that's an :alpha:
  3. a space
  4. an equals sign

This regex will get you most of the way there: [[:alpha:]]* = as it will highlight zero or more alpha characters before a 'space' and 'equals sign'.

You may need to use precedence to make this 'match' not appear for comment lines (which is what I assume you trying to do with the [^# ] command). Unfortunately, a single regex cannot fill the need to highlight a portion of a full-line match (I don't think).

  • 1
    Typically, you don't need to take comments into account since font-lock by default don't add a face if another one (i.e. the comment face) already is present. May 30, 2020 at 20:38

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