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gawk: Testing field creation

 
 4.8 Checking How 'gawk' Is Splitting Records
 ============================================
 
 As we've seen, 'gawk' provides three independent methods to split input
 records into fields.  The mechanism used is based on which of the three
 variables--'FS', 'FIELDWIDTHS', or 'FPAT'--was last assigned to.  In
 addition, an API input parser may choose to override the record parsing
 mechanism; please refer to ⇒Input Parsers for further information
 about this feature.
 
    To restore normal field splitting after using 'FIELDWIDTHS' and/or
 'FPAT', simply assign a value to 'FS'.  You can use 'FS = FS' to do
 this, without having to know the current value of 'FS'.
 
    In order to tell which kind of field splitting is in effect, use
 'PROCINFO["FS"]' (⇒Auto-set).  The value is '"FS"' if regular
 field splitting is being used, '"FIELDWIDTHS"' if fixed-width field
 splitting is being used, or '"FPAT"' if content-based field splitting is
 being used:
 
      if (PROCINFO["FS"] == "FS")
          REGULAR FIELD SPLITTING ...
      else if (PROCINFO["FS"] == "FIELDWIDTHS")
          FIXED-WIDTH FIELD SPLITTING ...
      else if (PROCINFO["FS"] == "FPAT")
          CONTENT-BASED FIELD SPLITTING ...
      else
          API INPUT PARSER FIELD SPLITTING ... (advanced feature)
 
    This information is useful when writing a function that needs to
 temporarily change 'FS' or 'FIELDWIDTHS', read some records, and then
 restore the original settings (⇒Passwd Functions for an example
 of such a function).
 
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