17639ba69SMichael Jones //===-- Linux implementation of isatty ------------------------------------===// 27639ba69SMichael Jones // 37639ba69SMichael Jones // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 47639ba69SMichael Jones // See https://llvm.org/LICENSE.txt for license information. 57639ba69SMichael Jones // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 67639ba69SMichael Jones // 77639ba69SMichael Jones //===----------------------------------------------------------------------===// 87639ba69SMichael Jones 97639ba69SMichael Jones #include "src/unistd/isatty.h" 107639ba69SMichael Jones 117639ba69SMichael Jones #include "src/__support/OSUtil/syscall.h" // For internal syscall function. 127639ba69SMichael Jones #include "src/__support/common.h" 137639ba69SMichael Jones 14*5ff3ff33SPetr Hosek #include "src/__support/macros/config.h" 15803437dbSMichael Jones #include "src/errno/libc_errno.h" 167639ba69SMichael Jones #include <sys/ioctl.h> // For ioctl numbers. 177639ba69SMichael Jones #include <sys/syscall.h> // For syscall numbers. 187639ba69SMichael Jones 19*5ff3ff33SPetr Hosek namespace LIBC_NAMESPACE_DECL { 207639ba69SMichael Jones 217639ba69SMichael Jones LLVM_LIBC_FUNCTION(int, isatty, (int fd)) { 227639ba69SMichael Jones constexpr int INIT_VAL = 0x1234abcd; 237639ba69SMichael Jones int line_d_val = INIT_VAL; 247639ba69SMichael Jones // This gets the line dicipline of the terminal. When called on something that 257639ba69SMichael Jones // isn't a terminal it doesn't change line_d_val and returns -1. 26f0a3954eSMichael Jones int result = 27b6bc9d72SGuillaume Chatelet LIBC_NAMESPACE::syscall_impl<int>(SYS_ioctl, fd, TIOCGETD, &line_d_val); 287639ba69SMichael Jones if (result == 0) 297639ba69SMichael Jones return 1; 307639ba69SMichael Jones 31204587a3SSiva Chandra Reddy libc_errno = -result; 327639ba69SMichael Jones return 0; 337639ba69SMichael Jones } 347639ba69SMichael Jones 35*5ff3ff33SPetr Hosek } // namespace LIBC_NAMESPACE_DECL 36