readBytesUntil() reads characters from a stream into a buffer. The function terminates if the terminator character is detected, the determined length has been read, or it times out (see setTimeout()). The function returns the characters up to the last character before the supplied terminator. The terminator itself is not returned in the buffer.

readBytesUntil() returns the number of bytes placed in the buffer. A 0 means no valid data was found.

This function is part of the Stream class, and can be called by any class that inherits from it (Wire, Serial, etc). See the Stream class main page for more information.


stream.readBytesUntil(character, buffer, length)


  • stream : an instance of a class that inherits from Stream.
  • character : the character to search for (char)
  • buffer: the buffer to store the bytes in (char[] or byte[])
  • length : the number of bytes to read(int)


  • The number of bytes placed in the buffer.

※ 주의 및 경고:

The terminator character is discarded from the stream.


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