std::strlen

 

C++

Language

Standard library headers

Concepts

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

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Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Technical Specifications

 

Strings library

Null-terminated strings

Byte strings

Multibyte strings

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Classes

basic_string

char_traits

 

Null-terminated byte strings

Functions
Character manipulation
isalnum isalpha islower isupper isdigit isxdigit isblank (C++11)	iscntrl isgraph isspace isprint ispunct tolower toupper
Conversions to numeric formats
atof atoiatolatoll strtolstrtoll	strtoulstrtoull strtofstrtodstrtold strtoimaxstrtouimax (C++11)(C++11)
String manipulation
strcpy
strncpy
strcat
strncat
strxfrm
String examination
strlen strcmp strncmp strcoll strchr strrchr	strspn strcspn strpbrk strstr strtok
Memory manipulation
memchr
memcmp
memset
memcpy
memmove
Miscellaneous
strerror

 

Defined in header <cstring>
std::size_t strlen( const char* str );

Returns the length of the given byte string, that is, the number of characters in a character array whose first element is pointed to by str up to and not including the first null character. The behavior is undefined if there is no null character in the character array pointed to by str.

Parameters

str

-

pointer to the null-terminated byte string to be examined

Return value

The length of the null-terminated string str.

Example

Run this code

#include <cstring>
#include <iostream>
 
int main()
{
   const char str[] = "How many characters does this string contain?";
 
   std::cout << "without null character: " << std::strlen(str) << '\n'
             << "with null character: " << sizeof str << '\n';
}

Output:

without null character: 45
with null character: 46

See also

wcslen	returns the length of a wide string (function)
mblen	returns the number of bytes in the next multibyte character (function)
C documentation for strlen