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+'\" t
+.\" Copyright 2008, Linux Foundation, written by Michael Kerrisk
+.\"     <mtk.manpages@gmail.com>
+.\"
+.\" SPDX-License-Identifier: Linux-man-pages-copyleft
+.\"
+.TH isatty 3 (date) "Linux man-pages (unreleased)"
+.SH NAME
+isatty \- test whether a file descriptor refers to a terminal
+.SH LIBRARY
+Standard C library
+.RI ( libc ", " \-lc )
+.SH SYNOPSIS
+.nf
+.B #include <unistd.h>
+.P
+.BI "int isatty(int " fd );
+.fi
+.SH DESCRIPTION
+The
+.BR isatty ()
+function tests whether
+.I fd
+is an open file descriptor referring to a terminal.
+.SH RETURN VALUE
+.BR isatty ()
+returns 1 if
+.I fd
+is an open file descriptor referring to a terminal;
+otherwise 0 is returned, and
+.I errno
+is set to indicate the error.
+.SH ERRORS
+.TP
+.B EBADF
+.I fd
+is not a valid file descriptor.
+.TP
+.B ENOTTY
+.I fd
+refers to a file other than a terminal.
+On some older kernels, some types of files
+.\" e.g., FIFOs and pipes on 2.6.32
+resulted in the error
+.B EINVAL
+in this case (which is a violation of POSIX, which specifies the error
+.BR ENOTTY ).
+.SH ATTRIBUTES
+For an explanation of the terms used in this section, see
+.BR attributes (7).
+.TS
+allbox;
+lbx lb lb
+l l l.
+Interface	Attribute	Value
+T{
+.na
+.nh
+.BR isatty ()
+T}	Thread safety	MT-Safe
+.TE
+.SH STANDARDS
+POSIX.1-2008.
+.SH HISTORY
+POSIX.1-2001, SVr4, 4.3BSD.
+.SH SEE ALSO
+.BR fstat (2),
+.BR ttyname (3)