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.\" ========================================================================
.\"
.IX Title "BIO_s_fd 3"
.TH BIO_s_fd 3 "2019-12-20" "1.0.2u" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
BIO_s_fd, BIO_set_fd, BIO_get_fd, BIO_new_fd \- file descriptor BIO
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/bio.h>
\&
\& BIO_METHOD *   BIO_s_fd(void);
\&
\& #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);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fBBIO_s_fd()\fR returns the file descriptor \s-1BIO\s0 method. This is a wrapper
round the platforms file descriptor routines such as \fBread()\fR and \fBwrite()\fR.
.PP
\&\fBBIO_read()\fR and \fBBIO_write()\fR read or write the underlying descriptor.
\&\fBBIO_puts()\fR is supported but \fBBIO_gets()\fR is not.
.PP
If the close flag is set then then \fBclose()\fR is called on the underlying
file descriptor when the \s-1BIO\s0 is freed.
.PP
\&\fBBIO_reset()\fR attempts to change the file pointer to the start of file
using lseek(fd, 0, 0).
.PP
\&\fBBIO_seek()\fR sets the file pointer to position \fBofs\fR from start of file
using lseek(fd, ofs, 0).
.PP
\&\fBBIO_tell()\fR returns the current file position by calling lseek(fd, 0, 1).
.PP
\&\fBBIO_set_fd()\fR sets the file descriptor of \s-1BIO\s0 \fBb\fR to \fBfd\fR and the close
flag to \fBc\fR.
.PP
\&\fBBIO_get_fd()\fR places the file descriptor in \fBc\fR if it is not \s-1NULL,\s0 it also
returns the file descriptor. If \fBc\fR is not \s-1NULL\s0 it should be of type
(int *).
.PP
\&\fBBIO_new_fd()\fR returns a file descriptor \s-1BIO\s0 using \fBfd\fR and \fBclose_flag\fR.
.SH "NOTES"
.IX Header "NOTES"
The behaviour of \fBBIO_read()\fR and \fBBIO_write()\fR depends on the behavior of the
platforms \fBread()\fR and \fBwrite()\fR calls on the descriptor. If the underlying 
file descriptor is in a non blocking mode then the \s-1BIO\s0 will behave in the
manner described in the \fBBIO_read\fR\|(3) and \fBBIO_should_retry\fR\|(3)
manual pages.
.PP
File descriptor BIOs should not be used for socket I/O. Use socket BIOs
instead.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBBIO_s_fd()\fR returns the file descriptor \s-1BIO\s0 method.
.PP
\&\fBBIO_reset()\fR returns zero for success and \-1 if an error occurred.
\&\fBBIO_seek()\fR and \fBBIO_tell()\fR return the current file position or \-1
if an error occurred. These values reflect the underlying \fBlseek()\fR
behaviour.
.PP
\&\fBBIO_set_fd()\fR always returns 1.
.PP
\&\fBBIO_get_fd()\fR returns the file descriptor or \-1 if the \s-1BIO\s0 has not
been initialized.
.PP
\&\fBBIO_new_fd()\fR returns the newly allocated \s-1BIO\s0 or \s-1NULL\s0 is an error
occurred.
.SH "EXAMPLE"
.IX Header "EXAMPLE"
This is a file descriptor \s-1BIO\s0 version of \*(L"Hello World\*(R":
.PP
.Vb 4
\& BIO *out;
\& out = BIO_new_fd(fileno(stdout), BIO_NOCLOSE);
\& BIO_printf(out, "Hello World\en");
\& BIO_free(out);
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBBIO_seek\fR\|(3), \fBBIO_tell\fR\|(3),
\&\fBBIO_reset\fR\|(3), \fBBIO_read\fR\|(3),
\&\fBBIO_write\fR\|(3), \fBBIO_puts\fR\|(3),
\&\fBBIO_gets\fR\|(3), \fBBIO_printf\fR\|(3),
\&\fBBIO_set_close\fR\|(3), \fBBIO_get_close\fR\|(3)