1ISATTY(3P)                 POSIX Programmer's Manual                ISATTY(3P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
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NAME

12       isatty — test for a terminal device
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SYNOPSIS

15       #include <unistd.h>
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17       int isatty(int fildes);
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DESCRIPTION

20       The isatty() function shall test whether fildes, an open file  descrip‐
21       tor, is associated with a terminal device.
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RETURN VALUE

24       The  isatty()  function  shall  return 1 if fildes is associated with a
25       terminal; otherwise, it shall return 0 and may set  errno  to  indicate
26       the error.
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ERRORS

29       The isatty() function may fail if:
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31       EBADF  The fildes argument is not a valid open file descriptor.
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33       ENOTTY The file associated with the fildes argument is not a terminal.
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35       The following sections are informative.
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EXAMPLES

38       None.
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APPLICATION USAGE

41       The  isatty() function does not necessarily indicate that a human being
42       is available for interaction via fildes.  It  is  quite  possible  that
43       non-terminal devices are connected to the communications line.
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RATIONALE

46       None.
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FUTURE DIRECTIONS

49       None.
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SEE ALSO

52       The Base Definitions volume of POSIX.1‐2017, <unistd.h>
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55       Portions  of  this text are reprinted and reproduced in electronic form
56       from IEEE Std 1003.1-2017, Standard for Information Technology --  Por‐
57       table  Operating System Interface (POSIX), The Open Group Base Specifi‐
58       cations Issue 7, 2018 Edition, Copyright (C) 2018 by the  Institute  of
59       Electrical  and  Electronics Engineers, Inc and The Open Group.  In the
60       event of any discrepancy between this version and the original IEEE and
61       The  Open Group Standard, the original IEEE and The Open Group Standard
62       is the referee document. The original Standard can be  obtained  online
63       at http://www.opengroup.org/unix/online.html .
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65       Any  typographical  or  formatting  errors that appear in this page are
66       most likely to have been introduced during the conversion of the source
67       files  to  man page format. To report such errors, see https://www.ker‐
68       nel.org/doc/man-pages/reporting_bugs.html .
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72IEEE/The Open Group                  2017                           ISATTY(3P)
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