man3/isatty.3

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  26 .TH ISATTY 3 2015-08-08 "Linux" "Linux Programmer's Manual"
  27 .SH NAME
  28 isatty \- test whether a file descriptor refers to a terminal
  29 .SH SYNOPSIS
  30 .nf
  31 .B #include <unistd.h>
  32 .PP
  33 .BI "int isatty(int " fd );
  34 .fi
  35 .SH DESCRIPTION
  36 The
  37 .BR isatty ()
  38 function tests whether
  39 .I fd
  40 is an open file descriptor referring to a terminal.
  41 .SH RETURN VALUE
  42 .BR isatty ()
  43 returns 1 if
  44 .I fd
  45 is an open file descriptor referring to a terminal;
  46 otherwise 0 is returned, and
  47 .I errno
  48 is set to indicate the error.
  49 .SH ERRORS
  50 .TP
  51 .B EBADF
  52 .I fd
  53 is not a valid file descriptor.
  54 .TP
  55 .B EINVAL
  56 .I fd
  57 refers to a file other than a terminal.
  58 POSIX.1 specifies the error
  59 .BR ENOTTY
  60 .\" FIXME . File a bug for this?
  61 for this case.
  62 .SH ATTRIBUTES
  63 For an explanation of the terms used in this section, see
  64 .BR attributes (7).
  65 .TS
  66 allbox;
  67 lb lb lb
  68 l l l.
  69 Interface       Attribute       Value
  70 T{
  71 .BR isatty ()
  72 T}      Thread safety   MT-Safe
  73 .TE
  74 .SH CONFORMING TO
  75 POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.
  76 .SH SEE ALSO
  77 .BR fstat (2),
  78 .BR ttyname (3)