1//! Functions which operate on file descriptors which might be terminals.
2
3use crate::backend;
4#[cfg(feature = "alloc")]
5#[cfg(feature = "fs")]
6#[cfg(not(any(target_os = "fuchsia", target_os = "wasi")))]
7use crate::path::SMALL_PATH_BUFFER_SIZE;
8use backend::fd::AsFd;
9#[cfg(feature = "alloc")]
10#[cfg(not(any(target_os = "fuchsia", target_os = "wasi")))]
11use {crate::ffi::CString, crate::io, alloc::vec::Vec, backend::fd::BorrowedFd};
12
13/// `isatty(fd)`—Tests whether a file descriptor refers to a terminal.
14///
15/// # References
16/// - [POSIX]
17/// - [Linux]
18///
19/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9799919799/functions/isatty.html
20/// [Linux]: https://man7.org/linux/man-pages/man3/isatty.3.html
21#[inline]
22pub fn isatty<Fd: AsFd>(fd: Fd) -> bool {
23 backend::termios::syscalls::isatty(fd.as_fd())
24}
25
26/// `ttyname_r(fd)`—Returns the name of the tty open on `fd`.
27///
28/// If `reuse` already has available capacity, reuse it if possible.
29///
30/// On Linux, this function depends on procfs being mounted on /proc.
31///
32/// # References
33/// - [POSIX]
34/// - [Linux]
35///
36/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9799919799/functions/ttyname.html
37/// [Linux]: https://man7.org/linux/man-pages/man3/ttyname.3.html
38#[cfg(not(any(target_os = "fuchsia", target_os = "wasi")))]
39#[cfg(feature = "alloc")]
40#[cfg(feature = "fs")]
41#[doc(alias = "ttyname_r")]
42#[cfg_attr(docsrs, doc(cfg(feature = "fs")))]
43#[cfg_attr(docsrs, doc(cfg(feature = "alloc")))]
44#[inline]
45pub fn ttyname<Fd: AsFd, B: Into<Vec<u8>>>(fd: Fd, reuse: B) -> io::Result<CString> {
46 _ttyname(fd.as_fd(), buffer:reuse.into())
47}
48
49#[cfg(not(any(target_os = "fuchsia", target_os = "wasi")))]
50#[cfg(feature = "alloc")]
51#[cfg(feature = "fs")]
52#[allow(unsafe_code)]
53fn _ttyname(fd: BorrowedFd<'_>, mut buffer: Vec<u8>) -> io::Result<CString> {
54 buffer.clear();
55 buffer.reserve(SMALL_PATH_BUFFER_SIZE);
56
57 loop {
58 match backend::termios::syscalls::ttyname(fd, buffer.spare_capacity_mut()) {
59 Err(io::Errno::RANGE) => {
60 // Use `Vec` reallocation strategy to grow capacity
61 // exponentially.
62 buffer.reserve(buffer.capacity() + 1);
63 }
64 Ok(len) => {
65 // SAFETY: Assume the backend returns the length of the string
66 // excluding the NUL.
67 unsafe {
68 buffer.set_len(len + 1);
69 }
70
71 // SAFETY:
72 // - “ttyname_r stores this pathname in the buffer buf”
73 // - [POSIX definition 3.271: Pathname]: “A string that is
74 // used to identify a file.”
75 // - [POSIX definition 3.375: String]: “A contiguous sequence
76 // of bytes terminated by and including the first null byte.”
77 //
78 // Thus, there will be a single NUL byte at the end of the
79 // string.
80 //
81 // [POSIX definition 3.271: Pathname]: https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/V1_chap03.html#tag_03_271
82 // [POSIX definition 3.375: String]: https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/V1_chap03.html#tag_03_375
83 unsafe {
84 return Ok(CString::from_vec_with_nul_unchecked(buffer));
85 }
86 }
87 Err(errno) => return Err(errno),
88 }
89 }
90}
91