BIO_s_fd() manual page.

diff --git a/doc/crypto/BIO_s_fd.pod b/doc/crypto/BIO_s_fd.pod
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+=pod
+
+=head1 NAME
+
+       BIO_s_fd - file descriptor BIO
+
+=head1 SYNOPSIS
+
+ #include <openssl/bio.h>
+
+ BIO_METHOD *  BIO_s_fd(void);
+
+ #define BIO_seek(b,ofs)       (int)BIO_ctrl(b,BIO_C_FILE_SEEK,ofs,NULL)
+ #define BIO_tell(b)           (int)BIO_ctrl(b,BIO_C_FILE_TELL,0,NULL)
+
+ #define BIO_set_fd(b,fd,c)    BIO_int_ctrl(b,BIO_C_SET_FD,c,fd)
+ #define BIO_get_fd(b,c)       BIO_ctrl(b,BIO_C_GET_FD,0,(char *)c)
+
+ BIO *BIO_new_fd(int fd, int close_flag);
+
+=head1 DESCRIPTION
+
+BIO_f_fd() returns the file descriptor BIO method. This is a wrapper
+round the platforms file descriptor routines such as read() and write().
+
+BIO_read() and BIO_write() read or write the underlying descriptor.
+BIO_puts() is supported but BIO_gets() is not.
+
+If the close flag is set then 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
+using lseek(fd, 0, 0).
+
+BIO_seek() sets the file pointer to position B<ofs> from start of file
+using lseek(fd, ofs, 0).
+
+BIO_tell() returns the current file position by calling lseek(fd, 0, 1).
+
+BIO_set_fd() sets the file descriptor of BIO B<b> to B<fd> and the close
+flag to B<c>.
+
+BIO_get_fd() places the file descriptor in B<c> if it is not NULL, it also
+returns the file descriptor. If B<c> is not NULL it should be of type
+(int *).
+
+BIO_new_fd() returns a file desciptor BIO using B<fd> and B<close_flag>.
+
+=head1 NOTES
+
+The behaviour of BIO_read() and BIO_write() depends on the behaviour 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 L<BIO_read(3)|BIO_read(3)> and L<BIO_should_retry(3)|BIO_should_retry(3)>
+manual pages.
+
+File descriptor BIOs should not be used for socket I/O. Use socket BIOs
+instead.
+
+=head1 RETURN VALUES
+
+BIO_s_fd() returns the file descriptor BIO method.
+
+BIO_reset() returns zero for success and -1 if an error occurred.
+BIO_seek() and BIO_tell() return the current file position or -1
+is an error occurred. These values reflect the underlying lseek()
+behaviour.
+
+BIO_set_fd() always returns 1.
+
+BIO_get_fd() returns the file descriptor or -1 if the BIO has not
+been initialised.
+
+BIO_new_fd() returns the newly allocated BIO or NULL is an error
+occurred.
+
+=head1 EXAMPLE
+
+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);
+
+=head1 SEE ALSO
+
+TBA