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.\" ========================================================================
.\"
.IX Title "BIO_S_FD 3"
.TH BIO_S_FD 3 "2023-09-11" "1.1.1w" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.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>
\&
\& 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);
.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_ex()\fR and \fBBIO_write_ex()\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 \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
such as by using \fBlseek(fd, 0, 0)\fR.
.PP
\&\fBBIO_seek()\fR sets the file pointer to position \fBofs\fR from start of file
such as by using \fBlseek(fd, ofs, 0)\fR.
.PP
\&\fBBIO_tell()\fR returns the current file position such as by calling
\&\fBlseek(fd, 0, 1)\fR.
.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.
.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_ex()\fR and \fBBIO_write_ex()\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_ex\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.
.PP
\&\fBBIO_set_fd()\fR and \fBBIO_get_fd()\fR are implemented as macros.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBBIO_s_fd()\fR returns the file descriptor \s-1BIO\s0 method.
.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 "EXAMPLES"
.IX Header "EXAMPLES"
This is a file descriptor \s-1BIO\s0 version of \*(L"Hello World\*(R":
.PP
.Vb 1
\& 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_ex\fR\|(3),
\&\fBBIO_write_ex\fR\|(3), \fBBIO_puts\fR\|(3),
\&\fBBIO_gets\fR\|(3), \fBBIO_printf\fR\|(3),
\&\fBBIO_set_close\fR\|(3), \fBBIO_get_close\fR\|(3)
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2000\-2019 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the OpenSSL license (the \*(L"License\*(R").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file \s-1LICENSE\s0 in the source distribution or at
<https://www.openssl.org/source/license.html>.