MatchData encapsulates the result of matching a Regexp against string. It is returned by Regexp#match and String#match, and also stored in a global variable returned by Regexp.last_match.
Usage:
url = 'https://docs.ruby-lang.org/en/2.5.0/MatchData.html'
m = url.match(/(\d\.?)+/) # => #<MatchData "2.5.0" 1:"0">
m.string # => "https://docs.ruby-lang.org/en/2.5.0/MatchData.html"
m.regexp # => /(\d\.?)+/
# entire matched substring:
m[0] # => "2.5.0"
# Working with unnamed captures
m = url.match(%r{([^/]+)/([^/]+)\.html$})
m.captures # => ["2.5.0", "MatchData"]
m[1] # => "2.5.0"
m.values_at(1, 2) # => ["2.5.0", "MatchData"]
# Working with named captures
m = url.match(%r{(?<version>[^/]+)/(?<module>[^/]+)\.html$})
m.captures # => ["2.5.0", "MatchData"]
m.named_captures # => {"version"=>"2.5.0", "module"=>"MatchData"}
m[:version] # => "2.5.0"
m.values_at(:version, :module)
# => ["2.5.0", "MatchData"]
# Numerical indexes are working, too
m[1] # => "2.5.0"
m.values_at(1, 2) # => ["2.5.0", "MatchData"]
Parts of last MatchData (returned by Regexp.last_match) are also aliased as global variables:
$~ is Regexp.last_match;
$& is Regexp.last_match[ 0 ];
$1, $2, and so on are Regexp.last_match[ i ] (captures by number);
$` is Regexp.last_match.pre_match;
$' is Regexp.last_match.post_match;
$+ is Regexp.last_match[ -1 ] (the last capture).
See also “Special global variables” section in Regexp documentation.
Equality—Two matchdata are equal if their target strings, patterns, and matched positions are identical.
static VALUE
match_aref(int argc, VALUE *argv, VALUE match)
{
VALUE idx, length;
match_check(match);
rb_scan_args(argc, argv, "11", &idx, &length);
if (NIL_P(length)) {
if (FIXNUM_P(idx)) {
return rb_reg_nth_match(FIX2INT(idx), match);
}
else {
int num = namev_to_backref_number(RMATCH_REGS(match), RMATCH(match)->regexp, idx);
if (num >= 0) {
return rb_reg_nth_match(num, match);
}
else {
return match_ary_aref(match, idx, Qnil);
}
}
}
else {
long beg = NUM2LONG(idx);
long len = NUM2LONG(length);
long num_regs = RMATCH_REGS(match)->num_regs;
if (len < 0) {
return Qnil;
}
if (beg < 0) {
beg += num_regs;
if (beg < 0) return Qnil;
}
else if (beg > num_regs) {
return Qnil;
}
else if (beg+len > num_regs) {
len = num_regs - beg;
}
return match_ary_subseq(match, beg, len, Qnil);
}
} Match Reference – MatchData acts as an array, and may be accessed using the normal array indexing techniques. mtch[0] is equivalent to the special variable $&, and returns the entire matched string. mtch[1], mtch[2], and so on return the values of the matched backreferences (portions of the pattern between parentheses).
m = /(.)(.)(\d+)(\d)/.match("THX1138.")
m #=> #<MatchData "HX1138" 1:"H" 2:"X" 3:"113" 4:"8">
m[0] #=> "HX1138"
m[1, 2] #=> ["H", "X"]
m[1..3] #=> ["H", "X", "113"]
m[-3, 2] #=> ["X", "113"]
m = /(?<foo>a+)b/.match("ccaaab")
m #=> #<MatchData "aaab" foo:"aaa">
m["foo"] #=> "aaa"
m[:foo] #=> "aaa"
static VALUE
match_begin(VALUE match, VALUE n)
{
int i = match_backref_number(match, n);
struct re_registers *regs = RMATCH_REGS(match);
match_check(match);
if (i < 0 || regs->num_regs <= i)
rb_raise(rb_eIndexError, "index %d out of matches", i);
if (BEG(i) < 0)
return Qnil;
update_char_offset(match);
return INT2FIX(RMATCH(match)->rmatch->char_offset[i].beg);
} Returns the offset of the start of the nth element of the match array in the string. n can be a string or symbol to reference a named capture.
m = /(.)(.)(\d+)(\d)/.match("THX1138.")
m.begin(0) #=> 1
m.begin(2) #=> 2
m = /(?<foo>.)(.)(?<bar>.)/.match("hoge")
p m.begin(:foo) #=> 0
p m.begin(:bar) #=> 2
static VALUE
match_captures(VALUE match)
{
return match_array(match, 1);
} Returns the array of captures; equivalent to mtch.to_a[1..-1].
f1,f2,f3,f4 = /(.)(.)(\d+)(\d)/.match("THX1138.").captures
f1 #=> "H"
f2 #=> "X"
f3 #=> "113"
f4 #=> "8"
static VALUE
match_end(VALUE match, VALUE n)
{
int i = match_backref_number(match, n);
struct re_registers *regs = RMATCH_REGS(match);
match_check(match);
if (i < 0 || regs->num_regs <= i)
rb_raise(rb_eIndexError, "index %d out of matches", i);
if (BEG(i) < 0)
return Qnil;
update_char_offset(match);
return INT2FIX(RMATCH(match)->rmatch->char_offset[i].end);
} Returns the offset of the character immediately following the end of the nth element of the match array in the string. n can be a string or symbol to reference a named capture.
m = /(.)(.)(\d+)(\d)/.match("THX1138.")
m.end(0) #=> 7
m.end(2) #=> 3
m = /(?<foo>.)(.)(?<bar>.)/.match("hoge")
p m.end(:foo) #=> 1
p m.end(:bar) #=> 3
static VALUE
match_equal(VALUE match1, VALUE match2)
{
const struct re_registers *regs1, *regs2;
if (match1 == match2) return Qtrue;
if (!RB_TYPE_P(match2, T_MATCH)) return Qfalse;
if (!RMATCH(match1)->regexp || !RMATCH(match2)->regexp) return Qfalse;
if (!rb_str_equal(RMATCH(match1)->str, RMATCH(match2)->str)) return Qfalse;
if (!rb_reg_equal(match_regexp(match1), match_regexp(match2))) return Qfalse;
regs1 = RMATCH_REGS(match1);
regs2 = RMATCH_REGS(match2);
if (regs1->num_regs != regs2->num_regs) return Qfalse;
if (memcmp(regs1->beg, regs2->beg, regs1->num_regs * sizeof(*regs1->beg))) return Qfalse;
if (memcmp(regs1->end, regs2->end, regs1->num_regs * sizeof(*regs1->end))) return Qfalse;
return Qtrue;
} Equality—Two matchdata are equal if their target strings, patterns, and matched positions are identical.
static VALUE
match_hash(VALUE match)
{
const struct re_registers *regs;
st_index_t hashval;
match_check(match);
hashval = rb_hash_start(rb_str_hash(RMATCH(match)->str));
hashval = rb_hash_uint(hashval, reg_hash(match_regexp(match)));
regs = RMATCH_REGS(match);
hashval = rb_hash_uint(hashval, regs->num_regs);
hashval = rb_hash_uint(hashval, rb_memhash(regs->beg, regs->num_regs * sizeof(*regs->beg)));
hashval = rb_hash_uint(hashval, rb_memhash(regs->end, regs->num_regs * sizeof(*regs->end)));
hashval = rb_hash_end(hashval);
return ST2FIX(hashval);
} Produce a hash based on the target string, regexp and matched positions of this matchdata.
See also Object#hash.
static VALUE
match_inspect(VALUE match)
{
VALUE cname = rb_class_path(rb_obj_class(match));
VALUE str;
int i;
struct re_registers *regs = RMATCH_REGS(match);
int num_regs = regs->num_regs;
struct backref_name_tag *names;
VALUE regexp = RMATCH(match)->regexp;
if (regexp == 0) {
return rb_sprintf("#<%"PRIsVALUE":%p>", cname, (void*)match);
}
else if (NIL_P(regexp)) {
return rb_sprintf("#<%"PRIsVALUE": %"PRIsVALUE">",
cname, rb_reg_nth_match(0, match));
}
names = ALLOCA_N(struct backref_name_tag, num_regs);
MEMZERO(names, struct backref_name_tag, num_regs);
onig_foreach_name(RREGEXP_PTR(regexp),
match_inspect_name_iter, names);
str = rb_str_buf_new2("#<");
rb_str_append(str, cname);
for (i = 0; i < num_regs; i++) {
VALUE v;
rb_str_buf_cat2(str, " ");
if (0 < i) {
if (names[i].name)
rb_str_buf_cat(str, (const char *)names[i].name, names[i].len);
else {
rb_str_catf(str, "%d", i);
}
rb_str_buf_cat2(str, ":");
}
v = rb_reg_nth_match(i, match);
if (v == Qnil)
rb_str_buf_cat2(str, "nil");
else
rb_str_buf_append(str, rb_str_inspect(v));
}
rb_str_buf_cat2(str, ">");
return str;
} Returns a printable version of mtch.
puts /.$/.match("foo").inspect
#=> #<MatchData "o">
puts /(.)(.)(.)/.match("foo").inspect
#=> #<MatchData "foo" 1:"f" 2:"o" 3:"o">
puts /(.)(.)?(.)/.match("fo").inspect
#=> #<MatchData "fo" 1:"f" 2:nil 3:"o">
puts /(?<foo>.)(?<bar>.)(?<baz>.)/.match("hoge").inspect
#=> #<MatchData "hog" foo:"h" bar:"o" baz:"g">
Returns the number of elements in the match array.
m = /(.)(.)(\d+)(\d)/.match("THX1138.")
m.length #=> 5
m.size #=> 5
static VALUE
match_named_captures(VALUE match)
{
VALUE hash;
struct MEMO *memo;
match_check(match);
if (NIL_P(RMATCH(match)->regexp))
return rb_hash_new();
hash = rb_hash_new();
memo = MEMO_NEW(hash, match, 0);
onig_foreach_name(RREGEXP(RMATCH(match)->regexp)->ptr, match_named_captures_iter, (void*)memo);
return hash;
} Returns a Hash using named capture.
A key of the hash is a name of the named captures. A value of the hash is a string of last successful capture of corresponding group.
m = /(?<a>.)(?<b>.)/.match("01")
m.named_captures #=> {"a" => "0", "b" => "1"}
m = /(?<a>.)(?<b>.)?/.match("0")
m.named_captures #=> {"a" => "0", "b" => nil}
m = /(?<a>.)(?<a>.)/.match("01")
m.named_captures #=> {"a" => "1"}
m = /(?<a>x)|(?<a>y)/.match("x")
m.named_captures #=> {"a" => "x"}
static VALUE
match_names(VALUE match)
{
match_check(match);
if (NIL_P(RMATCH(match)->regexp))
return rb_ary_new_capa(0);
return rb_reg_names(RMATCH(match)->regexp);
} Returns a list of names of captures as an array of strings. It is same as mtch.regexp.names.
/(?<foo>.)(?<bar>.)(?<baz>.)/.match("hoge").names
#=> ["foo", "bar", "baz"]
m = /(?<x>.)(?<y>.)?/.match("a") #=> #<MatchData "a" x:"a" y:nil>
m.names #=> ["x", "y"]
static VALUE
match_offset(VALUE match, VALUE n)
{
int i = match_backref_number(match, n);
struct re_registers *regs = RMATCH_REGS(match);
match_check(match);
if (i < 0 || regs->num_regs <= i)
rb_raise(rb_eIndexError, "index %d out of matches", i);
if (BEG(i) < 0)
return rb_assoc_new(Qnil, Qnil);
update_char_offset(match);
return rb_assoc_new(INT2FIX(RMATCH(match)->rmatch->char_offset[i].beg),
INT2FIX(RMATCH(match)->rmatch->char_offset[i].end));
} Returns a two-element array containing the beginning and ending offsets of the nth match. n can be a string or symbol to reference a named capture.
m = /(.)(.)(\d+)(\d)/.match("THX1138.")
m.offset(0) #=> [1, 7]
m.offset(4) #=> [6, 7]
m = /(?<foo>.)(.)(?<bar>.)/.match("hoge")
p m.offset(:foo) #=> [0, 1]
p m.offset(:bar) #=> [2, 3]
VALUE
rb_reg_match_post(VALUE match)
{
VALUE str;
long pos;
struct re_registers *regs;
if (NIL_P(match)) return Qnil;
match_check(match);
regs = RMATCH_REGS(match);
if (BEG(0) == -1) return Qnil;
str = RMATCH(match)->str;
pos = END(0);
str = rb_str_subseq(str, pos, RSTRING_LEN(str) - pos);
return str;
} Returns the portion of the original string after the current match. Equivalent to the special variable $'.
m = /(.)(.)(\d+)(\d)/.match("THX1138: The Movie")
m.post_match #=> ": The Movie"
VALUE
rb_reg_match_pre(VALUE match)
{
VALUE str;
struct re_registers *regs;
if (NIL_P(match)) return Qnil;
match_check(match);
regs = RMATCH_REGS(match);
if (BEG(0) == -1) return Qnil;
str = rb_str_subseq(RMATCH(match)->str, 0, BEG(0));
return str;
} Returns the portion of the original string before the current match. Equivalent to the special variable $`.
m = /(.)(.)(\d+)(\d)/.match("THX1138.")
m.pre_match #=> "T"
static VALUE
match_regexp(VALUE match)
{
VALUE regexp;
match_check(match);
regexp = RMATCH(match)->regexp;
if (NIL_P(regexp)) {
VALUE str = rb_reg_nth_match(0, match);
regexp = rb_reg_regcomp(rb_reg_quote(str));
RMATCH(match)->regexp = regexp;
}
return regexp;
} Returns the regexp.
m = /a.*b/.match("abc")
m.regexp #=> /a.*b/
static VALUE
match_size(VALUE match)
{
match_check(match);
return INT2FIX(RMATCH_REGS(match)->num_regs);
} Returns the number of elements in the match array.
m = /(.)(.)(\d+)(\d)/.match("THX1138.")
m.length #=> 5
m.size #=> 5
static VALUE
match_string(VALUE match)
{
match_check(match);
return RMATCH(match)->str; /* str is frozen */
} Returns a frozen copy of the string passed in to match.
m = /(.)(.)(\d+)(\d)/.match("THX1138.")
m.string #=> "THX1138."
static VALUE
match_to_a(VALUE match)
{
return match_array(match, 0);
} Returns the array of matches.
m = /(.)(.)(\d+)(\d)/.match("THX1138.")
m.to_a #=> ["HX1138", "H", "X", "113", "8"]
Because to_a is called when expanding *variable, there's a useful assignment shortcut for extracting matched fields. This is slightly slower than accessing the fields directly (as an intermediate array is generated).
all,f1,f2,f3 = * /(.)(.)(\d+)(\d)/.match("THX1138.")
all #=> "HX1138"
f1 #=> "H"
f2 #=> "X"
f3 #=> "113"
static VALUE
match_to_s(VALUE match)
{
VALUE str = rb_reg_last_match(match);
match_check(match);
if (NIL_P(str)) str = rb_str_new(0,0);
return str;
} Returns the entire matched string.
m = /(.)(.)(\d+)(\d)/.match("THX1138.")
m.to_s #=> "HX1138"
static VALUE
match_values_at(int argc, VALUE *argv, VALUE match)
{
VALUE result;
int i;
match_check(match);
result = rb_ary_new2(argc);
for (i=0; i<argc; i++) {
if (FIXNUM_P(argv[i])) {
rb_ary_push(result, rb_reg_nth_match(FIX2INT(argv[i]), match));
}
else {
int num = namev_to_backref_number(RMATCH_REGS(match), RMATCH(match)->regexp, argv[i]);
if (num >= 0) {
rb_ary_push(result, rb_reg_nth_match(num, match));
}
else {
match_ary_aref(match, argv[i], result);
}
}
}
return result;
} Uses each index to access the matching values, returning an array of the corresponding matches.
m = /(.)(.)(\d+)(\d)/.match("THX1138: The Movie")
m.to_a #=> ["HX1138", "H", "X", "113", "8"]
m.values_at(0, 2, -2) #=> ["HX1138", "X", "113"]
m = /(?<a>\d+) *(?<op>[+\-*\/]) *(?<b>\d+)/.match("1 + 2")
m.to_a #=> ["1 + 2", "1", "+", "2"]
m.values_at(:a, :b, :op) #=> ["1", "2", "+"]
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Licensed under the Ruby License.
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Licensed under their own licenses.