std::strncpy

C++

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Named requirements

Language support library

Concepts library (C++20)

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Strings library

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Numerics library

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Regular expressions library (C++11)

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Thread support library (C++11)

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Technical Specifications

Strings library

Null-terminated strings

Byte strings

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Classes

basic_string

basic_string_view (C++17)

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 (C++11) strtolstrtoll (C++11)	strtoulstrtoull (C++11) strtofstrtodstrtold (C++11)(C++11) 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>
char *strncpy( char *dest, const char *src, std::size_t count );

Copies at most count characters of the byte string pointed to by src (including the terminating null character) to character array pointed to by dest.

If count is reached before the entire string src was copied, the resulting character array is not null-terminated.

If, after copying the terminating null character from src, count is not reached, additional null characters are written to dest until the total of count characters have been written.

If the strings overlap, the behavior is undefined.

Parameters

dest	-	pointer to the character array to copy to
src	-	pointer to the byte string to copy from
count	-	maximum number of characters to copy

Return value

dest

Example

Run this code

#include <iostream>
#include <cstring>

int main()
{
    const char* src = "hi";
    char dest[6] = {'a', 'b', 'c', 'd', 'e', 'f'};
    std::strncpy(dest, src, 5);

    std::cout << "The contents of dest are: ";
    for (char c : dest) {
        if (c) {
            std::cout << c << ' ';
        } else {
            std::cout << "\\0" << ' ';
        }
    }
    std::cout << '\n';
}

Output:

The contents of dest are: h i \0 \0 \0 f

See also

strcpy	copies one string to another (function)
memcpy	copies one buffer to another (function)