Standard library header <cstring>

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Technical specifications

Symbols index

External libraries

 

Standard library headers

Language support
<cstddef> <cstdlib> <version> (C++20) <limits> <climits>	<cfloat> <cstdint> (C++11) <stdfloat> (C++23) <new> <typeinfo>	<source_location> (C++20) <exception> <initializer_list> (C++11) <compare> (C++20)	<coroutine> (C++20) <csignal> <csetjmp> <cstdarg>
Concepts
<concepts> (C++20)
Diagnostics
<stdexcept> <stacktrace> (C++23)	<cassert>	<cerrno>	<system_error> (C++11)
Memory management
<memory>	<memory_resource> (C++17)	<scoped_allocator> (C++11)
Metaprogramming
<type_traits> (C++11)	<ratio> (C++11)
General utilities
<utility> <tuple> (C++11) <optional> (C++17) <variant> (C++17)	<any> (C++17) <debugging> (C++26) <expected> (C++23) <bitset>	<functional> <typeindex> (C++11) <execution> (C++17)	<charconv> (C++17) <format> (C++20) <bit> (C++20)
Strings
<string_view> (C++17) <string>	<cctype> <cwctype>	<cstring> <cwchar>	<cuchar> (C++11)
Containers
<array> (C++11) <deque> <forward_list> (C++11) <list>	<vector> <map> <set> <unordered_map> (C++11)	<unordered_set> (C++11) <queue> <stack> <flat_map> (C++23)	<flat_set> (C++23) <span> (C++20) <mdspan> (C++23) <inplace_vector> (C++26)
Iterators
<iterator>
Ranges
<ranges> (C++20)	<generator> (C++23)
Algorithms
<algorithm>	<numeric>
Numerics
<cfenv> (C++11) <complex>	<random> (C++11) <valarray>	<cmath> <linalg> (C++26)	<numbers> (C++20)
Time
<chrono> (C++11)	<ctime>
Localization
<locale>	<clocale>	<codecvt> (C++11/17/26*)	<text_encoding> (C++26)
Input/output
<iosfwd> <iostream> <ios> <streambuf>	<istream> <ostream> <iomanip> <print> (C++23)	<sstream> <spanstream> (C++23) <fstream> <syncstream> (C++20)	<filesystem> (C++17) <cstdio> <cinttypes> (C++11) <strstream> (C++98/26*)
Regular expressions
<regex> (C++11)
Concurrency support
<stop_token> (C++20) <thread> (C++11) <atomic> (C++11) <rcu> (C++26)	<stdatomic.h> (C++23) <mutex> (C++11) <shared_mutex> (C++14)	<condition_variable> (C++11)   <semaphore> (C++20) <latch> (C++20)	<barrier> (C++20) <future> (C++11) <hazard_pointer> (C++26)
C compatibility
<cstdbool> (C++11/17/20*)   <ccomplex> (C++11/17/20*)	<ctgmath> (C++11/17/20*)	<cstdalign> (C++11/17/20*)	<ciso646> (until C++20)

 

This header was originally in the C standard library as <string.h>.

This header is for C-style null-terminated byte strings.

Macros

NULL	implementation-defined null pointer constant (macro constant)

Types

size_t

unsigned integer type returned by the sizeof operator (typedef)

Functions

String manipulation
strcpy	copies one string to another (function)
strncpy	copies a certain amount of characters from one string to another (function)
strcat	concatenates two strings (function)
strncat	concatenates a certain amount of characters of two strings (function)
strxfrm	transform a string so that strcmp would produce the same result as strcoll (function)
String examination
strlen	returns the length of a given string (function)
strcmp	compares two strings (function)
strncmp	compares a certain number of characters from two strings (function)
strcoll	compares two strings in accordance to the current locale (function)
strchr	finds the first occurrence of a character (function)
strrchr	finds the last occurrence of a character (function)
strspn	returns the length of the maximum initial segment that consists of only the characters found in another byte string (function)
strcspn	returns the length of the maximum initial segment that consists of only the characters not found in another byte string (function)
strpbrk	finds the first location of any character from a set of separators (function)
strstr	finds the first occurrence of a substring of characters (function)
strtok	finds the next token in a byte string (function)
Character array manipulation
memchr	searches an array for the first occurrence of a character (function)
memcmp	compares two buffers (function)
memset	fills a buffer with a character (function)
memcpy	copies one buffer to another (function)
memmove	moves one buffer to another (function)
Miscellaneous
strerror	returns a text version of a given error code (function)

Notes

• NULL is also defined in the following headers:
  • <clocale>
  • <ctime>
  • <cstddef>
  • <cstdio>
  • <cwchar>
• std::size_t is also defined in the following headers:
  • <ctime>
  • <cstddef>
  • <cstdio>
  • <cuchar> (since C++17)
  • <cwchar>

Synopsis

namespace std {
  using size_t = /* see description */;                  // freestanding
 
  void* memcpy(void* s1, const void* s2, size_t n);      // freestanding
  void* memmove(void* s1, const void* s2, size_t n);     // freestanding
  char* strcpy(char* s1, const char* s2);                // freestanding
  char* strncpy(char* s1, const char* s2, size_t n);     // freestanding
  char* strcat(char* s1, const char* s2);                // freestanding
  char* strncat(char* s1, const char* s2, size_t n);     // freestanding
  int memcmp(const void* s1, const void* s2, size_t n);  // freestanding
  int strcmp(const char* s1, const char* s2);            // freestanding
  int strcoll(const char* s1, const char* s2);
  int strncmp(const char* s1, const char* s2, size_t n); // freestanding
  size_t strxfrm(char* s1, const char* s2, size_t n);
  const void* memchr(const void* s, int c, size_t n);    // freestanding
  void* memchr(void* s, int c, size_t n);                // freestanding
  const char* strchr(const char* s, int c);              // freestanding
  char* strchr(char* s, int c);                          // freestanding
  size_t strcspn(const char* s1, const char* s2);        // freestanding
  const char* strpbrk(const char* s1, const char* s2);   // freestanding
  char* strpbrk(char* s1, const char* s2);               // freestanding
  const char* strrchr(const char* s, int c);             // freestanding
  char* strrchr(char* s, int c);                         // freestanding
  size_t strspn(const char* s1, const char* s2);         // freestanding
  const char* strstr(const char* s1, const char* s2);    // freestanding
  char* strstr(char* s1, const char* s2);                // freestanding
  char* strtok(char* s1, const char* s2);                // freestanding
  void* memset(void* s, int c, size_t n);                // freestanding
  char* strerror(int errnum);
  size_t strlen(const char* s);                          // freestanding
}
 
#define NULL /* see description */                       // freestanding