Replenish the input buffer and return the next character of input.
Declared in <bdls_fdstreambuf.h>
virtual
int_type
underflow() override;
Replenish the input buffer with data obtained from the file descriptor, and return the next character of input (or eof if no input is available). Note that in windows text mode, `\r ` sequences on the device will be translated to ` `s.
the next character of input, or eof if none is available