The Open Group Base Specifications Issue 6
IEEE Std 1003.1, 2003 Edition
Copyright © 2001-2003 The IEEE and The Open Group, All Rights reserved.

NAME

isatty - test for a terminal device

SYNOPSIS

#include <unistd.h>

int isatty(int fildes);

DESCRIPTION

The isatty() function shall test whether fildes, an open file descriptor, is associated with a terminal device.

RETURN VALUE

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

ERRORS

The isatty() function may fail if:

[EBADF]
The fildes argument is not a valid open file descriptor.
[ENOTTY]
The fildes argument is not associated with a terminal.
The following sections are informative.

EXAMPLES

None.

APPLICATION USAGE

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

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

The Base Definitions volume of IEEE Std 1003.1-2001, <unistd.h>

CHANGE HISTORY

First released in Issue 1. Derived from Issue 1 of the SVID.

Issue 6

The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:

End of informative text.
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POSIX ® is a registered Trademark of The IEEE.
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