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Library Function strlen in String Class
Library Function strlen of string.h Header File
On this page we will discuss about library function strlen in string class which is used in C. The C header file string.h contains a set of functions that can be used for performing various manipulation operations on strings. The strlen function is used to determine the length of a given string.
Library Function strlen in String Class used in C
In C programming language the strlen function is included in string.h header file.
The strlen function returns the number of characters in a string, but not including the null terminator.
Note:
In stlen function, the length of a given string consist of all the special characters, spaces, numbers, and alphabets.
Declaration of strlen function
int strlen(const char *str);
The strlen function can also be declared as:
size_t strlen(const char *str);
Here, strlen returns the length of the string as a size_t value.
Parameters of strlen function
The strcat function accepts single parameter which is str.
| Parameter | Description |
|---|---|
| str | It is a pointer to a null-terminated string. |
Return value of strlen function
The strlen function returns the length of the string as an integer value or of size_t value depending on the syntax used.
Implementation of Library Function string.h strlen
Example 1:
Run
#include <stdio.h>
#include <string.h>
int main() {
// Initializing string
char str[] = "Hello, world!";
//Using strlen() function
int len = strlen(str);
// Displaying the length of the string
printf("The length of the string is %d\n", len);
return 0;
}
Output:
The length of the string is 13.
Example 2:
Run
#include <stdio.h>
#include <string.h>
int main()
{
// Initializing string character by character
char p[30]={'P','r','e','p','I','n','s','t','a','\0'};
// Initializing strlen() function of size_t value.
// using the %zu format specifier to print size_t
printf("Length of the string p = %zu \n",strlen(p));
return 0;
}
Output:
Length of the string p = 9
Note
In C, the strlen function only counts the number of characters in the string, not including the null terminator at the end of the string. The null terminator is a character with the value '\0' that marks the end of the string.
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