Is this number a repdigit?

Brachylog, 1 byte

=

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This acts on integers.

From src/predicates.pl#L1151:

brachylog_equal('integer':0, 'integer':0, 'integer':0).
brachylog_equal('integer':0, 'integer':I, 'integer':I) :-
    H #\= 0,
    integer_value('integer':_:[H|T], I),
    brachylog_equal('integer':0, [H|T], [H|T]).

C (gcc), 33 30 29 bytes

f(n){n=n%100%11?9/n:f(n/10);}

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COBOL, 139 BYTES

I feel like COBOL doesn't get any love in code golfing (probably because there is no way it could win) but here goes:

IF A = ALL '1' OR ALL '2' OR ALL '3' OR ALL '4' OR ALL '5' OR
ALL '6' OR ALL '7' OR ALL '8' OR ALL '9' DISPLAY "TRUE" ELSE   
DISPLAY "FALSE".

A is defined as a PIC 9(4).