assign variable to char array

Projects Programming
1

Hi There , i feel i'm still in the newbie stage but know enough to get into trouble. I'm stuck with one section of code in my sketch that i need guidance on please.

I have written a sketch that retrieves a users configuration settings from a webserver and stores them as variables for use in the sketch. It uses IotWebConf.h and TelegramBot.h for this portion of the code. for %99 of the variables it works as intended however i'm struggling with the last one.

Where i'm stuck is i'm trying to add a variable to initilise the BotToken[] array ?

original and working code is :

const char BotToken[] = "This is where my bots API code is put"; // Defines bot token. Enter your Telegram bot token here.

However i want to change it to use a variable as per below :

 #define STRING_LEN 128

 char stringParamValue3[STRING_LEN];

 IotWebConfParameter stringParam3 = IotWebConfParameter("Telegram API Number", "Telegram API",   
 stringParamValue3, STRING_LEN, "password");

const char BotToken[] = stringParamValue3; // Basically just taken away the "" and added a known variable in its place

Doing so i end up with the below error on compile
initializer fails to determine size of 'BotToken'

So not really understanding whats going on i then try this :

#define STRING_LEN 128

 char stringParamValue3[STRING_LEN];

 IotWebConfParameter stringParam3 = IotWebConfParameter("Telegram API Number", "Telegram API", stringParamValue3, STRING_LEN, "password");

const char BotToken[128] {stringParamValue3}; // I added char length in the [] and added {} from what i was reading up on initializing a char array

I then end up with the error of :

invalid conversion from 'char*' to 'char' [-fpermissive]

Again not really understanding what is going on i try :

#define STRING_LEN 128

 char stringParamValue3[STRING_LEN];

 IotWebConfParameter stringParam3 = IotWebConfParameter("Telegram API Number", "Telegram API", stringParamValue3, STRING_LEN, "password");

const char* BotToken[128] {stringParamValue3}; // I added a * to make it const char*

now the errors moved to a different line of code in the sketch of

TelegramBot bot (BotToken, net_ssl);    // Adds library functions.

and the error is

no matching function for call to 'TelegramBot::TelegramBot(const char* [128], BearSSL::WiFiClientSecure&)'

As you can see i haven't grasped the concept of what is going on and feel like i'm just playing a game of trial and error.

Is it possible someone can guide me on whats going on here and how i go about correcting it please ?

Cheers

2 
const char BotToken[] = stringParamValue3;

That code is broken. Try this.

  1. Remove the const modifier from BotToken declaration. Otherwise, any attempt to modify its contents will fail.

  2. Provide a length in the declaration statement - BotToken[nn].*

char BotToken[128];
  1. Don't use '=' , use strcpy() to transfer the variable into BotToken.
3

Thanks for that , certainly put me on the right track. I don't have it working just yet but i have learn't something new today which is awesome thanks.

Currently i have :

char BotToken[70] ;
char strcpy(char BotToken,char stringParamValue3);

Serial.print(" BotToken in setup code is : ");
Serial.println(BotToken); // This doesn't show API number in the serial monitor
Serial.println(BotToken[0]); // This doesn't show API number either

Serial.print(" The actual var is : ");
Serial.println(stringParamValue3);// this shows me that the API number is in the actual variable

and it compiles ok now but as per the comments , Bottoken doesn't print out the token in the serial monitor. Have i miss read the instructions for strcpy() ?

cheers

4 
char strcpy(char BotToken,char stringParamValue3);

You don't need a function prototype for strcpy, it is provided for you in a header.
Yours is incorrect anyway.

5

I did a bit more research and now have it working by doing the following

char *my_strcpy(char *BotToken, char *stringParamValue3)
{
  char *start = BotToken;

  while (*stringParamValue3 != '\0')
  {
    *BotToken = *stringParamValue3;
    BotToken++;
    stringParamValue3++;
  }

  *BotToken = '\0'; // add '\0' at the end
  return start;



}

and trigger it by calling

my_strcpy(BotToken, stringParamValue3);

Thanks

6

Ummm. Why didn’t you just use strcpy since your version is doing the same thing (except for checking for overlapping source and destination)? Or...better yet strncpy because it is safer.