Making a String a certain length.

Projects Programming
1

Hi,

I am new to all this so please bear with me. My problem is that I need to turn a variable into a string with three digits.

e.g. I have a variable int called runs, which I need to convert to a string in order to output but it must be three digits long.

So my code is like this.

 int runs ;

String stringRuns = String(runs);

This works fine if the value of runs is 100 - 999, however if the value is 10 - 99 the string will be 2 digits long, if less than 10 only 1 digit long.

How can I force the string to include the leading zeroes?

2

mwtheplumber:
How can I force the string to include the leading zeroes?

use C style strings instead, along with sprintf/snprintf:

int runs = 99;

char string[4];

snprintf(string, "%03d", runs);  // Google: C++ format specifier

Serial.println(string);
3

which I need to convert to a string in order to output

As a matter of interest where is the output going to ?

4

The output is converted to a HEX string that goes to elctro-mechanical 7 digits displays via RS485

5

mwtheplumber:
...converted to a HEX string...

  char string[5];
  int data = 1010;
  snprintf(string, sizeof(string), "%04X", data);
  Serial.println(string);
6

Thanks for your help.

I have now progressed to putting three variables into 1 string which I can feed into the code to create the HEX string that will operate the numbers.

Code below which I have used to prove the concept.

void setup() {
  // put your setup code here, to run once:

 

 Serial.begin(19200);
}

void loop() {
  // put your main code here, to run repeatedly:

   int runs = 199;
    int wkts = 3;
     int overs = 24;

   char cruns [4];
   sprintf(cruns, "%03d", runs);

    char cwkts [4];
   sprintf(cwkts, "%03d", wkts);

    char covers [4];
   sprintf(covers, "%03d", overs);

   Serial.println(cruns);
   Serial.println(cwkts);
   Serial.println(covers);

   String StringRuns = String(cruns);
   String StringWkts = String(cwkts);
   String StringOvers = String(covers);
   String Output = String (StringRuns+StringWkts+StringOvers);
  

  Serial.print ("The runs are ");
  Serial.println(StringRuns);

   Serial.print ("The wkts are ");
  Serial.println(StringWkts);
   Serial.print ("The overs are ");
  Serial.println(StringOvers);
  Serial.println(Output);
  

  delay(1000);

}
7

Do you really need to convert the strings to Strings ?