How to Use String length()

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1/*
2
3  String length()
4
5  Examples of how to use length() in a String.
6
7  Open the Serial Monitor and start sending characters to see the results.
8
9  created 1 Aug 2010
10
11  by Tom Igoe
12
13  This example code is in the public domain.
14
15  https://www.arduino.cc/en/Tutorial/StringLengthTrim
16
17*/
18
19String txtMsg = "";                         // a string for incoming text
20unsigned int lastStringLength = txtMsg.length();     // previous length of the String
21
22void setup() {
23
24  // Open serial communications and wait for port to open:
25
26  Serial.begin(9600);
27
28  while (!Serial) {
29
30    ; // wait for serial port to connect. Needed for native USB port only
31
32  }
33
34  // send an intro:
35
36  Serial.println("\n\nString  length():");
37
38  Serial.println();
39}
40
41void loop() {
42
43  // add any incoming characters to the String:
44
45  while (Serial.available() > 0) {
46
47    char inChar = Serial.read();
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49    txtMsg += inChar;
50
51  }
52
53  // print the message and a notice if it's changed:
54
55  if (txtMsg.length() != lastStringLength) {
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57    Serial.println(txtMsg);
58
59    Serial.println(txtMsg.length());
60
61    // if the String's longer than 140 characters, complain:
62
63    if (txtMsg.length() < 140) {
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65      Serial.println("That's a perfectly acceptable text message");
66
67    } else {
68
69      Serial.println("That's too long for a text message.");
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71    }
72
73    // note the length for next time through the loop:
74
75    lastStringLength = txtMsg.length();
76
77  }
78}