Use the strlen() function provided by the C standard library string.h header file.

char name[7] = "Flavio";
strlen(name);

This function will return the length of a string as an integer value.

Working example:

#include <string.h>
#include <stdio.h>

int main(void) {
  char name[7] = "Flavio";
  int length = strlen(name);
  printf("Name length: %u", length);
}

Lessons in this unit:

0:	Introduction
1:	Input and output
2:	Variable scope
3:	Static variables
4:	Global variables
5:	Type definitions
6:	Enumerations
7:	Structures
8:	Command line parameters
9:	Header files
10:	The preprocessor
11:	NULL values
12:	Boolean values
13:	Nesting functions
14:	Conversion specifiers
15:	Using quotes
16:	▶︎ String length
17:	Returning strings
18:	Array length
19:	Looping through arrays
20:	Checking character values
21:	Printing percentage signs
22:	Troubleshooting: Implicit function declarations