1ISATTY(3)                  Linux Programmer's Manual                 ISATTY(3)
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NAME

6       isatty - test whether a file descriptor refers to a terminal
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SYNOPSIS

9       #include <unistd.h>
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11       int isatty(int fd);
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DESCRIPTION

14       The  isatty()  function tests whether fd is an open file descriptor re‐
15       ferring to a terminal.
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RETURN VALUE

18       isatty() returns 1 if fd is an open file descriptor referring to a ter‐
19       minal; otherwise 0 is returned, and errno is set to indicate the error.
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ERRORS

22       EBADF  fd is not a valid file descriptor.
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24       ENOTTY fd  refers  to a file other than a terminal.  On some older ker‐
25              nels, some types of files resulted in the error EINVAL  in  this
26              case  (which  is a violation of POSIX, which specifies the error
27              ENOTTY).
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ATTRIBUTES

30       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
31       tributes(7).
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33       ┌────────────────────────────────────────────┬───────────────┬─────────┐
34       │Interface                                   │ Attribute     │ Value   │
35       ├────────────────────────────────────────────┼───────────────┼─────────┤
36       │isatty()                                    │ Thread safety │ MT-Safe │
37       └────────────────────────────────────────────┴───────────────┴─────────┘
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CONFORMING TO

40       POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.
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SEE ALSO

43       fstat(2), ttyname(3)
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COLOPHON

46       This  page  is  part of release 5.13 of the Linux man-pages project.  A
47       description of the project, information about reporting bugs,  and  the
48       latest     version     of     this    page,    can    be    found    at
49       https://www.kernel.org/doc/man-pages/.
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53Linux                             2021-03-22                         ISATTY(3)
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