.\" Copyright (C) 2014 Michael Kerrisk <mtk.manpages@gmail.com>
.\"
.\" %%%LICENSE_START(VERBATIM)
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Permission is granted to copy and distribute modified versions of this
.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
.\" permission notice identical to this one.
.\"
.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date.  The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" the use of the information contained herein.  The author(s) may not
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
.\" professionally.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\" %%%LICENSE_END
.\"
.TH ISFDTYPE 3 2020-08-13 "Linux" "Linux Programmer's Manual"
.SH NAME
isfdtype \- test file type of a file descriptor
.SH SYNOPSIS
.nf
.B #include <sys/stat.h>
.B #include <sys/socket.h>
.PP
.BI "int isfdtype(int " fd ", int " fdtype );
.fi
.PP
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.PP
.BR isfdtype ():
.ad l
.RS 4
.PD 0
.TP 4
Since glibc 2.20:
_DEFAULT_SOURCE
.TP 4
Before glibc 2.20:
_BSD_SOURCE || _SVID_SOURCE
.PD
.RE
.ad b
.SH DESCRIPTION
The
.BR isfdtype ()
function tests whether the file descriptor
.I fd
refers to a file of type
.IR fdtype .
The
.I fdtype
argument specifies one of the
.B S_IF*
constants defined in
.I <sys/stat.h>
and documented in
.BR stat (2)
(e.g.,
.BR S_IFREG ).
.SH RETURN VALUE
The
.BR isfdtype ()
function returns 1 if the file descriptor
.I fd
is of type
.IR fdtype
and 0 if it is not.
On error, -1 is returned and
.I errno
is set to indicate the cause.
.SH ERRORS
The
.BR isfdtype ()
function can fail with any of the same errors as
.BR fstat (3).
.SH CONFORMING TO
The
.BR isfdtype ()
function is not specified in any standard,
but did appear in the draft POSIX.1g standard.
It is present on OpenBSD and Tru64 UNIX
(where the required header file in both cases is just
.IR <sys/stat.h> ,
as shown in the POSIX.1g draft),
and possibly other systems.
.SH NOTES
Portable applications should use
.BR fstat (3)
instead.
.SH SEE ALSO
.BR fstat (3)
.SH COLOPHON
This page is part of release 5.10 of the Linux
.I man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
\%https://www.kernel.org/doc/man\-pages/.