36 lines · cpp
1//===-- Linux implementation of isatty ------------------------------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8 9#include "src/unistd/isatty.h"10 11#include "src/__support/OSUtil/syscall.h" // For internal syscall function.12#include "src/__support/common.h"13 14#include "src/__support/libc_errno.h"15#include "src/__support/macros/config.h"16#include <sys/ioctl.h> // For ioctl numbers.17#include <sys/syscall.h> // For syscall numbers.18 19namespace LIBC_NAMESPACE_DECL {20 21LLVM_LIBC_FUNCTION(int, isatty, (int fd)) {22 constexpr int INIT_VAL = 0x1234abcd;23 int line_d_val = INIT_VAL;24 // This gets the line dicipline of the terminal. When called on something that25 // isn't a terminal it doesn't change line_d_val and returns -1.26 int result =27 LIBC_NAMESPACE::syscall_impl<int>(SYS_ioctl, fd, TIOCGETD, &line_d_val);28 if (result == 0)29 return 1;30 31 libc_errno = -result;32 return 0;33}34 35} // namespace LIBC_NAMESPACE_DECL36