sprintf(,"%f",); does not work, gives back %f

[holgerlembke]

void setup() {
Serial.begin(115200);
delay(5000);

float dog = 43.34567;

char *cat = new char[100] ;
sprintf(cat,"%f",dog);

Serial.println(cat);
}

void loop() {
delay(100);

}

Instead of a number I get "%f" back...

[chadouming]

This is a well known issue among arduino user

On Tue, May 26, 2015, 5:22 PM holgerlembke notifications@github.com wrote:

void setup() {
Serial.begin(115200);
delay(5000);

float dog = 43.34567;

char *cat = new char[100] ;
sprintf(cat,"%f",dog);

Serial.println(cat);
}

void loop() {
delay(100);

}

Instead of a number I get "%f" back...

—
Reply to this email directly or view it on GitHub
#341.

[holgerlembke]

And so we don't want to fix it?

Or at least document it? Perhaps create a Wiki page with "things that don't work"...

[chadouming]

you can use this function in the meantime

http://pastebin.com/FdBFk3F4

[holgerlembke]

Thanks, but coding some float to string is not the problem.

The problem is that every noob uses the printf/sprint with floats and wastes time to find the root of the problems, not really assuming that printf doesn't work with floats...

[igrr]

I think *printf style functions are not really Arduino way of doing things.
String class know how to handle conversion from floats, and this is what I
see used in most example sketches, at least those supplied with Arduino.

Having floats supported in printf would be nice for some use cases though.
If you feel like rolling such an implementation, replacing printfs we have
in ROM, please go ahead. Such contribution would be appreciated.
On May 27, 2015 12:07, "holgerlembke" notifications@github.com wrote:

Thanks, but coding some float to string is not the problem.

The problem is that every noob uses the printf/sprint with floats and
wastes time to find the root of the problems, not really assuming that
printf doesn't work with floats...

—
Reply to this email directly or view it on GitHub
#341 (comment).

[holgerlembke]

I think you are right with the String class way to go.

My "complain" is more about the lack of documentation and finding errors again and again that are well known. To others.

[ricardoquesada]

Probably due to ignorance, but I prefer to use a big snprintf than multiple String()s since my intuition tells me that String might take more resources and might be slower (just a guess).
If I have time I'll send a patch to support %f

[ghost]

printf with %f not working with 2.2.0. That is fixed in beta?

[sidewaiise]

Any progress on this issue? Was trying to use a snprintf() for debugging but %<l>.<p>f , %f and %F all seem not to work.