Can You Use strcmp to Compare Char Arrays?

Yes, strcmp is a powerful function in C for comparing character arrays (also known as strings). This function allows you to determine if two strings are equal or if one comes before the other lexicographically. This article will explain how strcmp works and demonstrate its usage within the context of the provided Arduino code example.

Understanding strcmp()

The strcmp() function, part of the standard C library (string.h), compares two null-terminated strings lexicographically. It takes two arguments:

• str1: The first string to be compared.
• str2: The second string to be compared.

strcmp() returns an integer value indicating the relationship between the two strings:

• 0: If str1 and str2 are identical.
• Less than 0: If str1 lexicographically precedes str2. (e.g., “apple” comes before “banana”).
• Greater than 0: If str1 lexicographically follows str2. (e.g., “zebra” comes after “apple”).

Applying strcmp() to the Arduino Code

The original code snippet aims to compare a received message (messageFromPC) against a list of 30 fixed strings. Currently, the code lacks a mechanism for this comparison. Let’s integrate strcmp() to achieve this functionality:

// ... (Existing code from the example) ...

// Array of fixed strings to compare against
const char* fixedStrings[] = {
  "String1", "String2", "String3", ..., "String30"
};

void showParsedData() {
  // ... (Existing printing code) ...

  // Compare messageFromPC against the fixed strings
  for (int i = 0; i < 30; i++) {
      if (strcmp(messageFromPC, fixedStrings[i]) == 0) {
          Serial.print("Match found: ");
          Serial.println(fixedStrings[i]);
          Serial.print("Integer from PC: ");
          Serial.println(integerFromPC);
          break; // Exit the loop after a match is found
      }
  }
}

This modified showParsedData() function now iterates through the fixedStrings array. In each iteration, strcmp() compares messageFromPC with the current fixed string. If a match is found (strcmp returns 0), the matching string and the integerFromPC are printed, and the loop terminates. If no match is found after checking all 30 strings, no action is taken, as per the original requirement.

Conclusion

strcmp() provides a concise and efficient way to compare character arrays in C. By incorporating strcmp() into the Arduino code, we’ve enabled the desired functionality of comparing the received message against a predefined list of strings, and responding accordingly. This method is far more efficient than a series of lengthy if/else statements, especially when dealing with a large number of comparisons. Remember that strcmp() is case-sensitive. If case-insensitive comparison is needed, consider using strcasecmp() (or stricmp() on some systems).