The RegSplit(pattern, text) command splits a string text at substrings matching the regular expression pattern. The sequence of substrings of text that remain after substrings of text that match pattern have been elided is returned.

Splitting the empty string on any regular expression yields the expression sequence NULL.

If the regular expression pattern matches the empty string, an exception is raised.

Empty strings may result when adjacent matches to pattern occur within text. These can be removed as shown in the examples below.

Use StringTools[Split] to split a string at any of a set of characters. (See the examples, below.) Although this can be accomplished with RegSplit, StringTools[Split] is more efficient for this special case.

All of the StringTools package commands treat strings as (null-terminated) sequences of $8$-bit (ASCII) characters.  Thus, there is no support for multibyte character encodings, such as unicode encodings.

$\mathrm{with}\left(\mathrm{StringTools}\right)\:$

$\mathrm{RegSplit}\left(''ab''\,''xabyabz''\right)$

$''x'',''y'',''z''$

$\mathrm{RegSplit}\left(''ab''\,''xababz''\right)$

$''x'','''',''z''$

$\mathrm{RegSplit}\left(''(a|b)''\,''xabyabz''\right)$

$''x'','''',''y'','''',''z''$

$\mathrm{RegSplit}\left(''(\backslash \backslash .|,|;)''\,''The\; Levi-Civita\; theorem\; provides\; a\; straightforward\; test\; for\; separability;\; however,\; because\; it\; is\; only\; a\; local\; characterization,\; it\; does\; not,\; in\; general,\; aid\; in\; the\; determination\; of\; separable\; coordinates.''\right)$

$''The\; Levi-Civita\; theorem\; provides\; a\; straightforward\; test\; for\; separability'',''however'',''because\; it\; is\; only\; a\; local\; characterization'',''it\; does\; not'',''in\; general'',''aid\; in\; the\; determination\; of\; separable\; coordinates''$

$\mathrm{RegSplit}\left(''[a-e]*''\,''xabyabz''\right)$

Error, (in StringTools:-RegSplit) empty string would match

$\mathrm{RegMatch}\left(''[a-e]*''\,''''\right)$

$\mathrm{true}$

$\mathrm{RegSplit}\left(''[a-e]+''\,''xabyabz''\right)$

$''x'',''y'',''z''$

$\mathrm{RegSplit}\left(''[a-e]''\,''xabyabz''\right)$

$''x'','''',''y'','''',''z''$

$\mathrm{RegSplit}\left(''[x-z]''\,''xabyabz''\right)$

$'''',''ab'',''ab''$

$\mathrm{Split}\left(''xabyabz''\,''abcde''\right)$

$\left[''x''\,''''\,''y''\,''''\,''z''\right]$

$\mathrm{remove}\left(\mathrm{type}\,\left[\mathrm{RegSplit}\right]\left(''ab''\,''abxabyabz''\right)\,''''\right)$

$\left[''x''\,''y''\,''z''\right]$