Method: String#rindex

Defined in:
string.c

#rindex(substring, offset = self.length) ⇒ Integer? #rindex(regexp, offset = self.length) ⇒ Integer?

Returns the Integer index of the last occurrence of the given substring, or nil if none found:

'foo'.rindex('f') # => 0
'foo'.rindex('o') # => 2
'foo'.rindex('oo') # => 1
'foo'.rindex('ooo') # => nil

Returns the Integer index of the last match for the given Regexp regexp, or nil if none found:

'foo'.rindex(/f/) # => 0
'foo'.rindex(/o/) # => 2
'foo'.rindex(/oo/) # => 1
'foo'.rindex(/ooo/) # => nil

Integer argument offset, if given and non-negative, specifies the maximum starting position in the

string to _end_ the search:
 'foo'.rindex('o', 0) # => nil
 'foo'.rindex('o', 1) # => 1
 'foo'.rindex('o', 2) # => 2
 'foo'.rindex('o', 3) # => 2

If offset is a negative Integer, the maximum starting position in the string to end the search is the sum of the string’s length and offset:

'foo'.rindex('o', -1) # => 2
'foo'.rindex('o', -2) # => 1
'foo'.rindex('o', -3) # => nil
'foo'.rindex('o', -4) # => nil

Related: String#index

Overloads:

  • #rindex(substring, offset = self.length) ⇒ Integer?

    Returns:

  • #rindex(regexp, offset = self.length) ⇒ Integer?

    Returns:

[View source]

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# File 'string.c', line 3865

static VALUE
rb_str_rindex_m(int argc, VALUE *argv, VALUE str)
{
    VALUE sub;
    VALUE vpos;
    rb_encoding *enc = STR_ENC_GET(str);
    long pos, len = str_strlen(str, enc); /* str's enc */

    if (rb_scan_args(argc, argv, "11", &sub, &vpos) == 2) {
	pos = NUM2LONG(vpos);
	if (pos < 0) {
	    pos += len;
	    if (pos < 0) {
		if (RB_TYPE_P(sub, T_REGEXP)) {
		    rb_backref_set(Qnil);
		}
		return Qnil;
	    }
	}
	if (pos > len) pos = len;
    }
    else {
	pos = len;
    }

    if (RB_TYPE_P(sub, T_REGEXP)) {
	/* enc = rb_get_check(str, sub); */
	pos = str_offset(RSTRING_PTR(str), RSTRING_END(str), pos,
			 enc, single_byte_optimizable(str));

	if (rb_reg_search(sub, str, pos, 1) >= 0) {
            VALUE match = rb_backref_get();
            struct re_registers *regs = RMATCH_REGS(match);
            pos = rb_str_sublen(str, BEG(0));
            return LONG2NUM(pos);
        }
    }
    else {
        StringValue(sub);
	pos = rb_str_rindex(str, sub, pos);
	if (pos >= 0) return LONG2NUM(pos);
    }
    return Qnil;
}