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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 referring to a terminal.

RETURN VALUE

isatty() returns 1 if fd is an open file descriptor referring to a terminal; otherwise 0 is returned, and errno is set to indicate the error.

ERRORS

fd is not a valid file descriptor.
fd refers to a file other than a terminal. On some older kernels, 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 attributes(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)

2022-10-09 Linux man-pages 6.01