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(gawk.info)Single Character Fields

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Making Each Character a Separate Field
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   There are times when you may want to examine each character of a
record separately.  This can be done in `gawk' by simply assigning the
null string (`""') to `FS'. In this case, each individual character in
the record becomes a separate field.  For example:

     $ echo a b | gawk 'BEGIN { FS = "" }
     >                  {
     >                      for (i = 1; i <= NF; i = i + 1)
     >                          print "Field", i, "is", $i
     >                  }'
     -| Field 1 is a
     -| Field 2 is
     -| Field 3 is b

   Traditionally, the behavior of `FS' equal to `""' was not defined.
In this case, most versions of Unix `awk' simply treat the entire record
as only having one field.  (d.c.)  In compatibility mode (Note:
Command-Line Options.), if `FS' is the null string, then
`gawk' also behaves this way.