isatty(3) Library Functions Manual isatty(3)
NAME
isatty - test whether a file descriptor refers to a terminal
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#include <unistd.h>
int isatty(int fd);
DESCRIPTION
The isatty() function tests whether fd is an open file descriptor re-
ferring to a terminal.
RETURN VALUE
isatty() returns 1 if fd is an open file descriptor referring to a ter-
minal; otherwise 0 is returned, and errno is set to indicate the error.
ERRORS
EBADF fd is not a valid file descriptor.
ENOTTY fd refers to a file other than a terminal. On some older ker-
nels, some types of files resulted in the error EINVAL in this
case (which is a violation of POSIX, which specifies the error
ENOTTY).
ATTRIBUTES
For an explanation of the terms used in this section, see at-
tributes(7).
┌────────────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├────────────────────────────────────────────┼───────────────┼─────────┤
│isatty() │ Thread safety │ MT-Safe │
└────────────────────────────────────────────┴───────────────┴─────────┘
STANDARDS
POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.
SEE ALSO
fstat(2), ttyname(3)
Linux man-pages 6.03 2022-12-15 isatty(3)
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