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   getentropy    ( 3 )

заполнить буфер случайными байтами (fill a buffer with random bytes)

Имя (Name)

getentropy - fill a buffer with random bytes

Синопсис (Synopsis)

#include <unistd.h>

int getentropy(void *buffer, size_t length);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

getentropy(): _DEFAULT_SOURCE


Описание (Description)

The getentropy() function writes length bytes of high-quality
       random data to the buffer starting at the location pointed to by
       buffer.  The maximum permitted value for the length argument is
       256.

A successful call to getentropy() always provides the requested number of bytes of entropy.


Возвращаемое значение (Return value)

On success, this function returns zero.  On error, -1 is
       returned, and errno is set to indicate the error.

Ошибки (Error)

EFAULT Part or all of the buffer specified by buffer and length
              is not in valid addressable memory.

EIO length is greater than 256.

EIO An unspecified error occurred while trying to overwrite buffer with random data.

ENOSYS This kernel version does not implement the getrandom(2) system call required to implement this function.


Версии (Versions)

The getentropy() function first appeared in glibc 2.25.

Стандарты (Conforming to)

This function is nonstandard.  It is also present on OpenBSD.

Примечание (Note)

The getentropy() function is implemented using getrandom(2).

Whereas the glibc wrapper makes getrandom(2) a cancellation point, getentropy() is not a cancellation point.

getentropy() is also declared in <sys/random.h>. (No feature test macro need be defined to obtain the declaration from that header file.)

A call to getentropy() may block if the system has just booted and the kernel has not yet collected enough randomness to initialize the entropy pool. In this case, getentropy() will keep blocking even if a signal is handled, and will return only once the entropy pool has been initialized.


Смотри также (See also)

getrandom(2), urandom(4), random(7)