End of Life Ruby 3.0 has reached end of life and gets no more fixes. Switch to Ruby 4.0 →
instance method
IO#ungetbyte
ios.ungetbyte(string) → nil
ios.ungetbyte(integer) → nil
io.c
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VALUE
rb_io_ungetbyte(VALUE io, VALUE b)
{
rb_io_t *fptr;
GetOpenFile(io, fptr);
rb_io_check_byte_readable(fptr);
switch (TYPE(b)) {
case T_NIL:
return Qnil;
case T_FIXNUM:
case T_BIGNUM: ;
VALUE v = rb_int_modulo(b, INT2FIX(256));
unsigned char c = NUM2INT(v) & 0xFF;
b = rb_str_new((const char *)&c, 1);
break;
default:
SafeStringValue(b);
}
io_ungetbyte(b, fptr);
return Qnil;
}
Pushes back bytes (passed as a parameter) onto ios, such that a subsequent buffered read will return it. Only one byte may be pushed back before a subsequent read operation (that is, you will be able to read only the last of several bytes that have been pushed back). Has no effect with unbuffered reads (such as IO#sysread).
Example
f = File.new("testfile") #=> #<File:testfile> b = f.getbyte #=> 0x38 f.ungetbyte(b) #=> nil f.getbyte #=> 0x38