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BIO_S_FD(3)                         OpenSSL                        BIO_S_FD(3)
NAME
       BIO_s_fd, BIO_set_fd, BIO_get_fd, BIO_new_fd - file descriptor BIO
SYNOPSIS
        #include <openssl/bio.h>
        const BIO_METHOD *BIO_s_fd(void);
        int BIO_set_fd(BIO *b, int fd, int c);
        int BIO_get_fd(BIO *b, int *c);
        BIO *BIO_new_fd(int fd, int close_flag);
DESCRIPTION
       BIO_s_fd() returns the file descriptor BIO method. This is a wrapper
       round the platforms file descriptor routines such as read() and
       write().
       BIO_read_ex() and BIO_write_ex() read or write the underlying
       descriptor.  BIO_puts() is supported but BIO_gets() is not.
       If the close flag is set then close() is called on the underlying file
       descriptor when the BIO is freed.
       BIO_reset() attempts to change the file pointer to the start of file
       such as by using lseek(fd, 0, 0).
       BIO_seek() sets the file pointer to position ofs from start of file
       such as by using lseek(fd, ofs, 0).
       BIO_tell() returns the current file position such as by calling
       lseek(fd, 0, 1).
       BIO_set_fd() sets the file descriptor of BIO b to fd and the close flag
       to c.
       BIO_get_fd() places the file descriptor in c if it is not NULL, it also
       returns the file descriptor.
       BIO_new_fd() returns a file descriptor BIO using fd and close_flag.
NOTES
       The behaviour of BIO_read_ex() and BIO_write_ex() depends on the
       behavior of the platforms read() and write() calls on the descriptor.
       If the underlying file descriptor is in a non blocking mode then the
       BIO will behave in the manner described in the BIO_read_ex(3) and
       BIO_should_retry(3) manual pages.
       File descriptor BIOs should not be used for socket I/O. Use socket BIOs
       instead.
       BIO_set_fd() and BIO_get_fd() are implemented as macros.
RETURN VALUES
       BIO_s_fd() returns the file descriptor BIO method.
       BIO_set_fd() always returns 1.
       BIO_get_fd() returns the file descriptor or -1 if the BIO has not been
       initialized.
       BIO_new_fd() returns the newly allocated BIO or NULL is an error
       occurred.
EXAMPLES
       This is a file descriptor BIO version of "Hello World":
        BIO *out;
        out = BIO_new_fd(fileno(stdout), BIO_NOCLOSE);
        BIO_printf(out, "Hello World\n");
        BIO_free(out);
SEE ALSO
       BIO_seek(3), BIO_tell(3), BIO_reset(3), BIO_read_ex(3),
       BIO_write_ex(3), BIO_puts(3), BIO_gets(3), BIO_printf(3),
       BIO_set_close(3), BIO_get_close(3)
COPYRIGHT
       Copyright 2000-2019 The OpenSSL Project Authors. All Rights Reserved.
       Licensed under the OpenSSL license (the "License").  You may not use
       this file except in compliance with the License.  You can obtain a copy
       in the file LICENSE in the source distribution or at
       <https://www.openssl.org/source/license.html>;.
1.1.1k                            2021-03-25                       BIO_S_FD(3)