Transform char array into String

Question

I have a function that returns a char array and I want that turned into a String so I can better process it (compare to other stored data). I am using this simple for that should work, but it doesn't for some reason (bufferPos is the length of the array, buffer is the array and item is an empty String):

for(int k=0; k<bufferPos; k++){
      item += buffer[k];
      }

The buffer has the right values and so does bufferPos, but when I try to convert, for example 544900010837154, it only holds 54. If I add Serial.prints to the for like this:

for(int k=0; k<bufferPos; k++){
                  Serial.print(buffer[k]);
                  Serial.print("\t");
                  Serial.println(item);
                  item += buffer[k];
                }

the output is this:

What am I missing? It feels like such a simple task and I fail to see the solution...

boop · Accepted Answer · 2019-11-17 20:49:59Z

36

If you have the char array null terminated, you can assign the char array to the string:

char[] chArray = "some characters";
String String(chArray);

As for your loop code, it looks right, but I will try on my controller to see if I get the same problem.

edited Nov 17, 2019 at 20:49

boop

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answered Jun 18, 2013 at 2:28

user2019047

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5 Comments

FloIancu Over a year ago

Thank you! For some reason str() didn't want to compile, but String() did and it works as intended.

Bruno Yuzo Over a year ago

'str' was not declared in this scope (Compiler 1.8.3)

Kenn Sebesta Over a year ago

Downvoting because str() is not an Arduino function. However, String() does indeed work so kudos to Flolancu.

Florian Burel Over a year ago

@KennSebesta : str(chArray) is not a function, it si the constructor. in c++ you dont do : String str = new String(chArray), you simply write String str(chArray)... does the same

thepirat000 Over a year ago

But the char array on your answer is not null terminated

Eswar · Accepted Answer · 2017-06-09 12:31:17Z

7

Visit https://www.arduino.cc/en/Reference/StringConstructor to solve the problem easily.

This worked for me:

char yyy[6];

String xxx;

yyy[0]='h';

yyy[1]='e';

yyy[2]='l';

yyy[3]='l';

yyy[4]='o';

yyy[5]='\0';

xxx=String(yyy);

edited Jun 9, 2017 at 12:31

user7605325

answered Jun 9, 2017 at 12:27

Eswar

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Comments

Rich Martin · Accepted Answer · 2016-10-28 19:11:15Z

Three years later, I ran into the same problem. Here's my solution, everybody feel free to cut-n-paste. The simplest things keep us up all night! Running on an ATMega, and Adafruit Feather M0:

void setup() {
  // turn on Serial so we can see...
  Serial.begin(9600);

  // the culprit:
  uint8_t my_str[6];    // an array big enough for a 5 character string

  // give it something so we can see what it's doing
  my_str[0] = 'H';
  my_str[1] = 'e';
  my_str[2] = 'l';
  my_str[3] = 'l';
  my_str[4] = 'o';
  my_str[5] = 0;  // be sure to set the null terminator!!!

  // can we see it?
  Serial.println((char*)my_str);

  // can we do logical operations with it as-is?
  Serial.println((char*)my_str == 'Hello');

  // okay, it can't; wrong data type (and no terminator!), so let's do this:
  String str((char*)my_str);

  // can we see it now?
  Serial.println(str);

  // make comparisons
  Serial.println(str == 'Hello');

  // one more time just because
  Serial.println(str == "Hello");

  // one last thing...!
  Serial.println(sizeof(str));
}

void loop() {
  // nothing
}

And we get:

Hello    // as expected
0        // no surprise; wrong data type and no terminator in comparison value
Hello    // also, as expected
1        // YAY!
1        // YAY!
6        // as expected

Hope this helps someone!

praks411 · Accepted Answer · 2013-06-18 11:07:22Z

0

May you should try creating a temp string object and then add to existing item string. Something like this.

for(int k=0; k<bufferPos; k++){
      item += String(buffer[k]);
      }

answered Jun 18, 2013 at 11:07

praks411

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Comments

sunshinestyle · Accepted Answer · 2014-12-03 07:48:45Z

-1

I have search it again and search this question in baidu. Then I find 2 ways:

1,

char ch[]={'a','b','c','d','e','f','g','\0'};
string s=ch;
cout<<s;

Be aware to that '\0' is necessary for char array ch.

2,

#include<iostream>
#include<string>
#include<strstream>
using namespace std;

int main()
{
	char ch[]={'a','b','g','e','d','\0'};
	strstream s;
	s<<ch;
	string str1;
	s>>str1;
	cout<<str1<<endl;
	return 0;
}

In this way, you also need to add the '\0' at the end of char array.

Also, strstream.h file will be abandoned and be replaced by stringstream

answered Dec 3, 2014 at 7:48

sunshinestyle

1

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