`strdup.3p` ( 3 )

дублировать определенное количество байтов из строки (duplicate a specific number of bytes from a string)

Пролог (Prolog)

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

Имя (Name)

strdup, strndup — duplicate a specific number of bytes from a string

Синопсис (Synopsis)

#include <string.h>

char *strdup(const char *s); char *strndup(const char *s, size_t size);

Описание (Description)

The strdup() function shall return a pointer to a new string, which is a duplicate of the string pointed to by s. The returned pointer can be passed to free(). A null pointer is returned if the new string cannot be created.

The strndup() function shall be equivalent to the strdup() function, duplicating the provided s in a new block of memory allocated as if by using malloc(), with the exception being that strndup() copies at most size plus one bytes into the newly allocated memory, terminating the new string with a NUL character. If the length of s is larger than size, only size bytes shall be duplicated. If size is larger than the length of s, all bytes in s shall be copied into the new memory buffer, including the terminating NUL character. The newly created string shall always be properly terminated.

Возвращаемое значение (Return value)

The strdup() function shall return a pointer to a new string on success. Otherwise, it shall return a null pointer and set errno to indicate the error.

Upon successful completion, the strndup() function shall return a pointer to the newly allocated memory containing the duplicated string. Otherwise, it shall return a null pointer and set errno to indicate the error.

Ошибки (Error)

These functions shall fail if:

ENOMEM Storage space available is insufficient.

The following sections are informative.

Примеры (Examples)

None.

Использование в приложениях (Application usage)

For functions that allocate memory as if by malloc(), the application should release such memory when it is no longer required by a call to free(). For strdup() and strndup(), this is the return value.

Implementations are free to malloc() a buffer containing either (size + 1) bytes or (strnlen( s, size) + 1) bytes. Applications should not assume that strndup() will allocate (size + 1) bytes when strlen( s) is smaller than size.

Обоснование (Rationale)

None.

Будущие направления (Future directions)