POSIX implementation specifics

In KasperskyOS, the specific implementation of some POSIX interfaces not entirely defined by the POSIX.1-2008 standard differs from the implementation of these interfaces in Linux and other UNIX-like operating systems. Information about these interfaces is provided in the table below.

POSIX interfaces and their implementation specifics

Interface	Purpose	Implementation	Header file based on the POSIX.1-2008 standard
`bind()`	Assign a name to a socket.	When using a VFS version that supports only network operations, files of sockets in the `AF_UNIX` family are saved in a special file system implemented by this VFS version when `bind()` is called. A socket file can be created only in the root of the file system or in the `/tmp` directory, and it can be re-used after the socket is closed.	`sys/socket.h`
`mmap()`	Map to memory.	The `MAP_FIXED` flag in the `flags` parameter is not supported. Mapping more than 4 GB is not supported on hardware platforms running an AArch64 (Arm64) processor architecture.	`sys/mman.h`
`read()`	Read from a file.	If the size of the `buf` buffer exceeds the size of the read data, the remainder of this buffer is filled with zeros.	`unistd.h`
`poll()`	Track the state of file handles.	You cannot combine invalid file handles (for example, closed handles, unavailable handles, or handles with invalid values) with a negative `timeout` parameter value (unlimited timeout). In this case, the function returns `-1`, and `errno` is set to `EINVAL`.	`sys/poll.h`
`select()`	Track the state of file handles.	You cannot call a function with null values for all parameters. In this case, the function returns `-1`, and `errno` is set to `EINVAL`.	`sys/select.h`
`fcntl()`	Perform operations with a file handle.	The Linux-specific `F_SETPIPE_SZ` and `F_GETPIPE_SZ` macros are supported.	`fcntl.h`

In KasperskyOS, the errno variable can take the values of both standard POSIX error codes and those specific to KasperskyOS. For information about error codes specific to KasperskyOS, see Return codes.

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