Arduino trim: does it remove the \n as well?

Question

According to the manual:

https://www.arduino.cc/en/Reference/StringTrim

Trim strips one or more whitespaces from the beginning and the end. Does it also removes tabulators and \n ?

I have the following code which works:

 while (Serial.available()) {   // something came across the serial   
      char c = (char)Serial.read();
      Command += c;
      Command.trim();
      if (c=='\n')
         {
           Complete =true;
         }   
   if (Command.length() >0 && Complete) {

        if (Command == "LED_ON") {
               // Do stuff
        }       

Although I'm not sure that it is working because of the last if statement which says: if (Command == "LED_ON") ignores the ending \n and say ok it matched OR Command.trim() really takes off that \n.

Thank you

Answer 1

Yes, \n is also removed.

The source for the trim() function is in WString.cpp.

void String::trim(void)
{
    if (!buffer || len == 0) return;
    char *begin = buffer;
    while (isspace(*begin)) begin++;
    char *end = buffer + len - 1;
    while (isspace(*end) && end >= begin) end--;
    len = end + 1 - begin;
    if (begin > buffer) memcpy(buffer, begin, len);
    buffer[len] = 0;
}

We can see it uses the isspace() function, but where's that function defined? WString.cpp only #includes WString.h, so we go there.

In WString.h, we can see it includes ctype.h. Time to go to the C++ Reference, which tells us that yes, \n is a "space" according to isspace(), so it is trimmed.

(note that isspace() is affected by localization settings. I'm not sure what the localization settings are when compiling for Arduino)

Answer 2

Whilst rchard2scout is quite right that trim will remove newlines, why not rearrange the code so it doesn't matter?

  char c = (char)Serial.read();
  if (c == '\n')
     Complete = true;
  else
     Command += c;