How to set a char array to a specific spot in a 2d char array

Projects Programming
21

I'm still trying to figure out Arduino code the only coding language I know really well is python

22

here's my code pasted into the foroms directly

#include <SD.h>

int chipSelect = 4;
char bdaylist[2][6][13];// this use to be bdaylist[50][6][13] buy with strncpy i had to chaenge it
File file;

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

  pinMode(chipSelect, OUTPUT);
  while(true){
    if (SD.begin(chipSelect)){
      Serial.println("SD Card initialize.");
      break;
    }else{
      Serial.println("Could not initialize SD Card.");
    }
  }
  if(SD.exists("bdays.txt")){
    Serial.println("card contanse the birthday list");
    file = SD.open("bdays.txt", FILE_READ);
    char character;
    char charBuf[13];
    String word;
    int row = 0;
    int col = 0;
    while ((character = file.read()) != -1){
      if(character == '|'){
        Serial.println();
        Serial.print("word = ");
        Serial.println(word);
        word.toCharArray(charBuf, 13);
        Serial.print("charBuf = ");
        Serial.println(charBuf);
        word = "";
        
        Serial.println();
        Serial.print("bdaylist[");
        Serial.print(row);
        Serial.print("][");
        Serial.print(col);
        Serial.print("] = ");
        
        //strcpy(&bdaylist[0][1], charBuf, sizeof(charBuf));
        strncpy(bdaylist[row][col], charBuf, sizeof(charBuf));
        Serial.println(bdaylist[row][col]);
        col++;
      }
      else if(character == '\n'){
        Serial.println();
        Serial.print("word = ");
        Serial.println(word);
        word.toCharArray(charBuf, 13);
        Serial.print("charBuf = ");
        Serial.println(charBuf);
        word = "";
        
        Serial.println();
        Serial.print("bdaylist[");
        Serial.print(row);
        Serial.print("][");
        Serial.print(col);
        Serial.print("] = ");
        //strcpy(&bdaylist[0][1], charBuf, sizeof(charBuf));
        strncpy(bdaylist[row][col], charBuf, sizeof(charBuf));
        Serial.print(bdaylist[row][col]);
        
        //Serial.println();
        row++;
      }else{
        word = word+character;
      }
      //Serial.println();
    }
    Serial.println();
    file.close();
    Serial.println("--reading ended--");
    
    for(int r=0;r<2;r++){
      for(int c=0;c<6;c++){
        Serial.print("<");
        Serial.print(bdaylist[r][c]);
        Serial.print(">\t");
      }
      Serial.println();
    }
    
    Serial.println("--end--");
  }
}

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

}
23

strcpy doesn’t take 3 arguments

24

Don’t use the size with strcpy

25

Basically you want to use this strlcpy which is safer than strcpy and strncpy

size_t strlcpy( char *dst,
                const char *src,
                size_t size );

See https://www.qnx.com/developers/docs/7.1/#com.qnx.doc.neutrino.lib_ref/topic/s/strlcat.html for important notes

So you need the pointer to somewhere in memory where you have enough bytes to copy your charbuf content including the trailing null.

If you need a 2D array containing the texts, then indeed you need to define a 3D array, the last dimension being for the bytes of the data

const size_t nbCols = 30;
const size_t nbRows = 10;
const size_t maxTextLength = 12;
char storage[nbRows][nbCols][maxTextLength+1]; // +1 for the trailing null char

Note that this array uses up 30x10x12 bytes that is 3600 bytes. Depending on your arduino it’s a lot, It won’t fit on a UNO for example.

The destination pointer to the memory location where you have the bytes available can be given by the first part of the array, for example

storage[3][5]

Or by taking the address or the first byte

&(storage[3][5][0])

This would be the address of 4th row and 7th column (indexes start at 0).

And if you use strlcpy() then the size at that location is maxTextLength+1

To fill up the charbuf array you have only maxTextLength bytes available and you keep the +1 byte always for the trailing null if your text reaches max capacity

26

I figured it out I am reading only one line of the text file on the SD card instead of storing it into a 3d array thanks for the help.

this forum is solved no need to post anymore. thank you all. good bye.

27

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