Question

Can split(string, array, separator) in awk use sequence of whitespaces as the separator (or more generally any regexp as the separator)?

Obviously, one could use the internal autosplit (that runs on each line of the input with value of FS variable as the separator) and with simple for and $0 magic do the trick. However, I was just wondering if there’s a more straightforward way using the splititself.

Answer 1

The GNU Awk User’s Guide states:

split(string, array, fieldsep)

This divides string into pieces separated by fieldsep, and stores the
pieces in array. The first piece is stored in array[1], the second
piece in array[2], and so forth. The string value of the third
argument, fieldsep, is a regexp describing where to split string (much
as FS can be a regexp describing where to split input records). If
the fieldsep is omitted, the value of FS is used. split returns the
number of elements created. The split function, then, splits strings
into pieces in a manner similar to the way input lines are split into
fields

Here is a short (somewhat silly) example that uses a simple regular expression ".s " that will match any single character followed by a lower-case s and a space. The result of the split is put into array a. Note that the parts that match are not placed into the array.

BEGIN { 
  s = "this isn't a string yes isodore?"
  count = split(s, a, ".s ")
  printf("number of splits: %d\n", count)

  print "Contents of array:"
  for (i = 1; i <= count; i++) 
    printf "a[%d]: %s\n", i, a[i]
}

The output:

$ awk -f so.awk

number of splits: 3
Contents of array:
a[1]: th
a[2]: isn't a string y
a[3]: isodore?

The article Advanced Awk for Sysadmins show an example of parsing a line using split(). This page contains an example of using a regular expression to split data into
an array.