isatty(3) Library Functions Manual isatty(3) isatty - (libc -lc) #include int isatty(int fd); isatty() fd . isatty() 1 fd 0 errno . EBADF fd . ENOTTY fd . EINVAL ( POSIX ENOTTY). attributes(7). +------------+------------------------------------+--------------------+ || | | +------------+------------------------------------+--------------------+ |isatty() | | MT-Safe | +------------+------------------------------------+--------------------+ POSIX.1-2008. POSIX.1-2001 SVr4 4.3BSD. fstat(2), ttyname(3) 3 . . : . 6.18 17 2025 isatty(3)