In RTF, { and } marks a group. Groups can be nested. \ marks beginning of a control word. Control words end with either a space or a non alphabetic character. A control word can have a numeric parameter following, without any delimiter in between. Some control words also take text parameters, separated by ';'. Those control words are usually in their own groups.
I think I have managed to make a pattern that takes care of most the cases.
\{\*?\\[^{}]+}|[{}]|\\\n?[A-Za-z]+\n?(?:-?\d+)?[ ]?
It leaves a few spaces when run on your pattern though.
Going trough the RTF specification (some of it), I see that there are a lot of pitfalls for pure regex based strippers. The most obvious one are that some groups should be ignored (headers, footers, etc.), while others should be rendered (formatting).
I have written a Python script that should work better than my regex above:
def striprtf(text):
pattern = re.compile(r"\\([a-z]{1,32})(-?\d{1,10})?[ ]?|\\'([0-9a-f]{2})|\\([^a-z])|([{}])|[\r\n]+|(.)", re.I)
# control words which specify a "destionation".
destinations = frozenset((
'aftncn','aftnsep','aftnsepc','annotation','atnauthor','atndate','atnicn','atnid',
'atnparent','atnref','atntime','atrfend','atrfstart','author','background',
'bkmkend','bkmkstart','blipuid','buptim','category','colorschememapping',
'colortbl','comment','company','creatim','datafield','datastore','defchp','defpap',
'do','doccomm','docvar','dptxbxtext','ebcend','ebcstart','factoidname','falt',
'fchars','ffdeftext','ffentrymcr','ffexitmcr','ffformat','ffhelptext','ffl',
'ffname','ffstattext','field','file','filetbl','fldinst','fldrslt','fldtype',
'fname','fontemb','fontfile','fonttbl','footer','footerf','footerl','footerr',
'footnote','formfield','ftncn','ftnsep','ftnsepc','g','generator','gridtbl',
'header','headerf','headerl','headerr','hl','hlfr','hlinkbase','hlloc','hlsrc',
'hsv','htmltag','info','keycode','keywords','latentstyles','lchars','levelnumbers',
'leveltext','lfolevel','linkval','list','listlevel','listname','listoverride',
'listoverridetable','listpicture','liststylename','listtable','listtext',
'lsdlockedexcept','macc','maccPr','mailmerge','maln','malnScr','manager','margPr',
'mbar','mbarPr','mbaseJc','mbegChr','mborderBox','mborderBoxPr','mbox','mboxPr',
'mchr','mcount','mctrlPr','md','mdeg','mdegHide','mden','mdiff','mdPr','me',
'mendChr','meqArr','meqArrPr','mf','mfName','mfPr','mfunc','mfuncPr','mgroupChr',
'mgroupChrPr','mgrow','mhideBot','mhideLeft','mhideRight','mhideTop','mhtmltag',
'mlim','mlimloc','mlimlow','mlimlowPr','mlimupp','mlimuppPr','mm','mmaddfieldname',
'mmath','mmathPict','mmathPr','mmaxdist','mmc','mmcJc','mmconnectstr',
'mmconnectstrdata','mmcPr','mmcs','mmdatasource','mmheadersource','mmmailsubject',
'mmodso','mmodsofilter','mmodsofldmpdata','mmodsomappedname','mmodsoname',
'mmodsorecipdata','mmodsosort','mmodsosrc','mmodsotable','mmodsoudl',
'mmodsoudldata','mmodsouniquetag','mmPr','mmquery','mmr','mnary','mnaryPr',
'mnoBreak','mnum','mobjDist','moMath','moMathPara','moMathParaPr','mopEmu',
'mphant','mphantPr','mplcHide','mpos','mr','mrad','mradPr','mrPr','msepChr',
'mshow','mshp','msPre','msPrePr','msSub','msSubPr','msSubSup','msSubSupPr','msSup',
'msSupPr','mstrikeBLTR','mstrikeH','mstrikeTLBR','mstrikeV','msub','msubHide',
'msup','msupHide','mtransp','mtype','mvertJc','mvfmf','mvfml','mvtof','mvtol',
'mzeroAsc','mzeroDesc','mzeroWid','nesttableprops','nextfile','nonesttables',
'objalias','objclass','objdata','object','objname','objsect','objtime','oldcprops',
'oldpprops','oldsprops','oldtprops','oleclsid','operator','panose','password',
'passwordhash','pgp','pgptbl','picprop','pict','pn','pnseclvl','pntext','pntxta',
'pntxtb','printim','private','propname','protend','protstart','protusertbl','pxe',
'result','revtbl','revtim','rsidtbl','rxe','shp','shpgrp','shpinst',
'shppict','shprslt','shptxt','sn','sp','staticval','stylesheet','subject','sv',
'svb','tc','template','themedata','title','txe','ud','upr','userprops',
'wgrffmtfilter','windowcaption','writereservation','writereservhash','xe','xform',
'xmlattrname','xmlattrvalue','xmlclose','xmlname','xmlnstbl',
'xmlopen',
))
# Translation of some special characters.
specialchars = {
'par': '\n',
'sect': '\n\n',
'page': '\n\n',
'line': '\n',
'tab': '\t',
'emdash': u'\u2014',
'endash': u'\u2013',
'emspace': u'\u2003',
'enspace': u'\u2002',
'qmspace': u'\u2005',
'bullet': u'\u2022',
'lquote': u'\u2018',
'rquote': u'\u2019',
'ldblquote': u'\201C',
'rdblquote': u'\u201D',
}
stack = []
ignorable = False # Whether this group (and all inside it) are "ignorable".
ucskip = 1 # Number of ASCII characters to skip after a unicode character.
curskip = 0 # Number of ASCII characters left to skip
out = [] # Output buffer.
for match in pattern.finditer(text):
word,arg,hex,char,brace,tchar = match.groups()
if brace:
curskip = 0
if brace == '{':
# Push state
stack.append((ucskip,ignorable))
elif brace == '}':
# Pop state
ucskip,ignorable = stack.pop()
elif char: # \x (not a letter)
curskip = 0
if char == '~':
if not ignorable:
out.append('\n')
elif char in '{}\\':
if not ignorable:
out.append(char)
elif char == '*':
ignorable = True
elif word: # \foo
curskip = 0
if word in destinations:
ignorable = True
elif ignorable:
pass
elif word in specialchars:
out.append(specialchars[word])
elif word == 'uc':
ucskip = int(arg)
elif word == 'u':
c = int(arg)
if c < 0: c += 0x10000
if c > 127: out.append(unichr(c))
else: out.append(chr(c))
curskip = ucskip
elif hex: # \'xx
if curskip > 0:
curskip -= 1
elif not ignorable:
c = int(hex,16)
if c > 127: out.append(unichr(c))
else: out.append(chr(c))
elif tchar:
if curskip > 0:
curskip -= 1
elif not ignorable:
out.append(tchar)
return ''.join(out)
It works by parsing the RTF code, and skipping any groups which has a "destination" specified, and all "ignorable" groups ({\*...}). I also added handling of some special characters.
There are lots of features missing to make this a full parser, but should be enough for simple documents.