Looks for the next valid integer in the incoming serial. The function terminates if it times out (see Serial.setTimeout()).

Serial.parseInt() inherits from the Stream utility class.

In particular:

  • Parsing stops when no characters have been read for a configurable time-out value, or a non-digit is read;
  • If no valid digits were read when the time-out (see Serial.setTimeout()) occurs, 0 is returned;




Serial.parseInt(lookahead, ignore)

Parameter Values

  • Serial: serial port object. See the list of available serial ports for each board on the Serial main page.
  • lookahead: the mode used to look ahead in the stream for an integer. Allowed data types: LookaheadMode. Allowed lookahead values:
    • SKIP_ALL: all characters other than digits or a minus sign are ignored when scanning the stream for an integer. This is the default mode.
    • SKIP_NONE: Nothing is skipped, and the stream is not touched unless the first waiting character is valid.
    • SKIP_WHITESPACE: Only tabs, spaces, line feeds, and carriage returns are skipped.
  • ignore: used to skip the indicated char in the search. Used for example to skip thousands divider. Allowed data types: char

Return Values

  • The next valid integer. Data type: long.

Example Code

void setup() { Serial.begin(9600); } void loop() { if (Serial.available() > 0) { long myInt = Serial.parseInt(SKIP_ALL, '\n'); // prints the received integer Serial.print("I received: "); Serial.println(myInt); } }
  • Compile and upload the above code to Arduino
  • Open Serial Monitor and select Newline option
  • Type -125 on Serial Monitor and click Send button:
  • COM6
    Autoscroll Show timestamp
    Clear output
    9600 baud  
  • The result on Serial Monitor:
  • COM6
    I received: -125
    Autoscroll Show timestamp
    Clear output
    9600 baud  


Serial functions are not only used for the communication between an Arduino board and Serial Monitor of Arduino IDE but also used for the communication between:

  • An Arduino board and other Arduino board
  • An Arduino board and other sensors/devices
  • An Arduino board and computer (any Serial software on computer)

See Also


Arduino UNO R3
Arduino Starter Kit
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