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How to format an integer as 3 digit string? If I give 3 formated string should be 003

printf("%03d\n", 3); // output: 003

This doesn't work in Arduino.

user119o
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  • You can use `sprintf` with a `char` array buffer and then pass it to `Serial.print()`. – jfpoilpret Feb 21 '17 at 16:51
  • Thanks its worked, 'char buff[3]; sprintf (buff,"%03d",3); Serial.print(buff);' – user119o Feb 21 '17 at 17:07
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    Rather use `char buff[4]` as you need one byte for the terminating zero that will be added by `sprintf`. If you don't, it may overwrite some value in your stack, leading to hard to understand problems. – jfpoilpret Feb 21 '17 at 17:12
  • Or you could [setup `printf()` to print through `Serial`](http://arduino.stackexchange.com/a/480). This way you don't have to allocate room for `sprintf()`, which can be (as you just experienced) error prone. – Edgar Bonet Feb 21 '17 at 18:10
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    BTW, you will need more than 4 chars if the number you print happens to be less than -99 or more than 999. With `buffer[7]` you can safely print any `int`, and with `buffer[12]` you can print any `long`. – Edgar Bonet Feb 21 '17 at 20:53
  • See this if you have a lot of strings and don't want them using up the limited amount of RAM. https://www.arduino.cc/en/Reference/PROGMEM – Gregg Aug 08 '17 at 19:59

1 Answers1

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The standard C function printf print to stdout. Arduino doesn't has a stdout. You can print to Serial, but must prepare/format the string first.

Instead of printf, use snprintf. It prints to a char array, which you later can use with Serial.print, or whatever other function that take a string.

void setup() {
  Serial.begin(9600);
  while(!Serial);

  char buffer[4];
  snprintf(buffer,sizeof(buffer), "%03d", 3);
  Serial.println(buffer);
}

void loop() {

}

Note: all the comments apply to this answers.