xref: /aosp_15_r20/external/llvm-libc/src/unistd/linux/isatty.cpp (revision 71db0c75aadcf003ffe3238005f61d7618a3fead)
1*71db0c75SAndroid Build Coastguard Worker //===-- Linux implementation of isatty ------------------------------------===//
2*71db0c75SAndroid Build Coastguard Worker //
3*71db0c75SAndroid Build Coastguard Worker // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4*71db0c75SAndroid Build Coastguard Worker // See https://llvm.org/LICENSE.txt for license information.
5*71db0c75SAndroid Build Coastguard Worker // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6*71db0c75SAndroid Build Coastguard Worker //
7*71db0c75SAndroid Build Coastguard Worker //===----------------------------------------------------------------------===//
8*71db0c75SAndroid Build Coastguard Worker 
9*71db0c75SAndroid Build Coastguard Worker #include "src/unistd/isatty.h"
10*71db0c75SAndroid Build Coastguard Worker 
11*71db0c75SAndroid Build Coastguard Worker #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
12*71db0c75SAndroid Build Coastguard Worker #include "src/__support/common.h"
13*71db0c75SAndroid Build Coastguard Worker 
14*71db0c75SAndroid Build Coastguard Worker #include "src/__support/macros/config.h"
15*71db0c75SAndroid Build Coastguard Worker #include "src/errno/libc_errno.h"
16*71db0c75SAndroid Build Coastguard Worker #include <sys/ioctl.h>   // For ioctl numbers.
17*71db0c75SAndroid Build Coastguard Worker #include <sys/syscall.h> // For syscall numbers.
18*71db0c75SAndroid Build Coastguard Worker 
19*71db0c75SAndroid Build Coastguard Worker namespace LIBC_NAMESPACE_DECL {
20*71db0c75SAndroid Build Coastguard Worker 
21*71db0c75SAndroid Build Coastguard Worker LLVM_LIBC_FUNCTION(int, isatty, (int fd)) {
22*71db0c75SAndroid Build Coastguard Worker   constexpr int INIT_VAL = 0x1234abcd;
23*71db0c75SAndroid Build Coastguard Worker   int line_d_val = INIT_VAL;
24*71db0c75SAndroid Build Coastguard Worker   // This gets the line dicipline of the terminal. When called on something that
25*71db0c75SAndroid Build Coastguard Worker   // isn't a terminal it doesn't change line_d_val and returns -1.
26*71db0c75SAndroid Build Coastguard Worker   int result =
27*71db0c75SAndroid Build Coastguard Worker       LIBC_NAMESPACE::syscall_impl<int>(SYS_ioctl, fd, TIOCGETD, &line_d_val);
28*71db0c75SAndroid Build Coastguard Worker   if (result == 0)
29*71db0c75SAndroid Build Coastguard Worker     return 1;
30*71db0c75SAndroid Build Coastguard Worker 
31*71db0c75SAndroid Build Coastguard Worker   libc_errno = -result;
32*71db0c75SAndroid Build Coastguard Worker   return 0;
33*71db0c75SAndroid Build Coastguard Worker }
34*71db0c75SAndroid Build Coastguard Worker 
35*71db0c75SAndroid Build Coastguard Worker } // namespace LIBC_NAMESPACE_DECL
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