C language strlen () function usage

C language strlen () function: Returns the length of a string

Header files: #include <string.h>

The strlen () function is used to calculate the length of a string, and its prototype is: unsigned int strlen (char *s); s for the specified string

eg

#include <stdio.h> #include <string.h>int main () {    char *str1 = "http://see.xidian.edu.cn/cpp/u/shipin/";    Char str2[100] = "http://see.xidian.edu.cn/cpp/u/shipin_liming/";    Char str3[5] = "12345";    printf ("strlen (str1) =%d, sizeof (STR1) =%d\n", strlen (str1), sizeof (STR1));    printf ("strlen (str2) =%d, sizeof (STR2) =%d\n", strlen (str2), sizeof (STR2));    printf ("strlen (STR3) =%d, sizeof (STR3) =%d\n", strlen (STR3), sizeof (STR3));    return 0;}
Operation Result:
Strlen (str1) =38, sizeof (STR1) =4
Strlen (str1) =45, sizeof (STR1) =100
Strlen (str1) =53, sizeof (STR1) =5

if the number of characters equals the size of the character array, then the return value of strlen () cannot be determined , for example
Char str[6] = "ABCXYZ";
The return value of strlen (str) will be indeterminate. Because the end of STR is not 0,strlen () will continue to retrieve backwards until it encounters ' \ ' and the contents of these areas are indeterminate.

C language strlen () function usage