isatty(3)

1isatty(3)                  Library Functions Manual                  isatty(3)
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NAME

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

9       Standard C library (libc, -lc)
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SYNOPSIS

12       #include <unistd.h>
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14       int isatty(int fd);
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DESCRIPTION

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

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

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

33       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
34       tributes(7).
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36       ┌────────────────────────────────────────────┬───────────────┬─────────┐
37       │Interface                                   │ Attribute     │ Value   │
38       ├────────────────────────────────────────────┼───────────────┼─────────┤
39       │isatty()                                    │ Thread safety │ MT-Safe │
40       └────────────────────────────────────────────┴───────────────┴─────────┘
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STANDARDS

43       POSIX.1-2008.
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HISTORY

46       POSIX.1-2001, SVr4, 4.3BSD.
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