rustix/io/
dup.rs

1//! Functions which duplicate file descriptors.
2
3use crate::fd::OwnedFd;
4use crate::{backend, io};
5use backend::fd::AsFd;
6
7#[cfg(not(target_os = "wasi"))]
8pub use backend::io::types::DupFlags;
9
10/// `dup(fd)`—Creates a new `OwnedFd` instance that shares the same
11/// underlying [file description] as `fd`.
12///
13/// This function does not set the `O_CLOEXEC` flag. To do a `dup` that does
14/// set `O_CLOEXEC`, use [`fcntl_dupfd_cloexec`].
15///
16/// POSIX guarantees that `dup` will use the lowest unused file descriptor,
17/// however it is not safe in general to rely on this, as file descriptors may
18/// be unexpectedly allocated on other threads or in libraries.
19///
20/// # References
21///  - [POSIX]
22///  - [Linux]
23///  - [Apple]
24///  - [FreeBSD]
25///  - [NetBSD]
26///  - [OpenBSD]
27///  - [DragonFly BSD]
28///  - [illumos]
29///  - [glibc]
30///
31/// [file description]: https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/V1_chap03.html#tag_03_258
32/// [`fcntl_dupfd_cloexec`]: crate::io::fcntl_dupfd_cloexec
33/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9799919799/functions/dup.html
34/// [Linux]: https://man7.org/linux/man-pages/man2/dup.2.html
35/// [Apple]: https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man2/dup.2.html
36/// [FreeBSD]: https://man.freebsd.org/cgi/man.cgi?query=dup&sektion=2
37/// [NetBSD]: https://man.netbsd.org/dup.2
38/// [OpenBSD]: https://man.openbsd.org/dup.2
39/// [DragonFly BSD]: https://man.dragonflybsd.org/?command=dup&section=2
40/// [illumos]: https://illumos.org/man/2/dup
41/// [glibc]: https://sourceware.org/glibc/manual/latest/html_node/Duplicating-Descriptors.html
42#[cfg(not(target_os = "wasi"))]
43#[inline]
44pub fn dup<Fd: AsFd>(fd: Fd) -> io::Result<OwnedFd> {
45    backend::io::syscalls::dup(fd.as_fd())
46}
47
48/// `dup2(fd, new)`—Changes the [file description] of a file descriptor.
49///
50/// `dup2` conceptually closes `new` and then sets the file description for
51/// `new` to be the same as the one for `fd`. This is a very unusual operation,
52/// and should only be used on file descriptors where you know how `new` will
53/// be subsequently used.
54///
55/// This function does not set the `O_CLOEXEC` flag. To do a `dup2` that does
56/// set `O_CLOEXEC`, use [`dup3`] with [`DupFlags::CLOEXEC`] on platforms which
57/// support it, or [`fcntl_dupfd_cloexec`].
58///
59/// For `dup2` to stdin, stdout, and stderr, see [`stdio::dup2_stdin`],
60/// [`stdio::dup2_stdout`], and [`stdio::dup2_stderr`].
61///
62/// # References
63///  - [POSIX]
64///  - [Linux]
65///  - [Apple]
66///  - [FreeBSD]
67///  - [NetBSD]
68///  - [OpenBSD]
69///  - [DragonFly BSD]
70///  - [illumos]
71///  - [glibc]
72///
73/// [file description]: https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/V1_chap03.html#tag_03_258
74/// [`fcntl_dupfd_cloexec`]: crate::io::fcntl_dupfd_cloexec
75/// [POSIX]: https://pubs.opengroup.org/onlinepubs/9799919799/functions/dup2.html
76/// [Linux]: https://man7.org/linux/man-pages/man2/dup2.2.html
77/// [Apple]: https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man2/dup2.2.html
78/// [FreeBSD]: https://man.freebsd.org/cgi/man.cgi?query=dup2&sektion=2
79/// [NetBSD]: https://man.netbsd.org/dup2.2
80/// [OpenBSD]: https://man.openbsd.org/dup2.2
81/// [DragonFly BSD]: https://man.dragonflybsd.org/?command=dup2&section=2
82/// [illumos]: https://illumos.org/man/2/dup
83/// [glibc]: https://sourceware.org/glibc/manual/latest/html_node/Duplicating-Descriptors.html
84/// [`stdio::dup2_stdin`]: https://docs.rs/rustix/*/rustix/stdio/fn.dup2_stdin.html
85/// [`stdio::dup2_stdout`]: https://docs.rs/rustix/*/rustix/stdio/fn.dup2_stdout.html
86/// [`stdio::dup2_stderr`]: https://docs.rs/rustix/*/rustix/stdio/fn.dup2_stderr.html
87#[cfg(not(target_os = "wasi"))]
88#[inline]
89pub fn dup2<Fd: AsFd>(fd: Fd, new: &mut OwnedFd) -> io::Result<()> {
90    backend::io::syscalls::dup2(fd.as_fd(), new)
91}
92
93/// `dup3(fd, new, flags)`—Changes the [file description] of a file
94/// descriptor, with flags.
95///
96/// `dup3` is the same as [`dup2`] but adds an additional flags operand, and it
97/// fails in the case that `fd` and `new` have the same file descriptor value.
98/// This additional difference is the reason this function isn't named
99/// `dup2_with`.
100///
101/// # References
102///  - [Linux]
103///  - [FreeBSD]
104///  - [NetBSD]
105///  - [OpenBSD]
106///  - [DragonFly BSD]
107///
108/// [file description]: https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/V1_chap03.html#tag_03_258
109/// [Linux]: https://man7.org/linux/man-pages/man2/dup3.2.html
110/// [FreeBSD]: https://man.freebsd.org/cgi/man.cgi?query=dup3&sektion=3
111/// [NetBSD]: https://man.netbsd.org/dup3.2
112/// [OpenBSD]: https://man.openbsd.org/dup3.2
113/// [DragonFly BSD]: https://man.dragonflybsd.org/?command=dup3&section=3
114#[cfg(not(any(
115    target_os = "aix",
116    target_os = "espidf",
117    target_os = "horizon",
118    target_os = "nto",
119    target_os = "vita",
120    target_os = "wasi"
121)))]
122#[inline]
123pub fn dup3<Fd: AsFd>(fd: Fd, new: &mut OwnedFd, flags: DupFlags) -> io::Result<()> {
124    backend::io::syscalls::dup3(fd.as_fd(), new, flags)
125}
rustix/io/dup.rs

rustix/io/
dup.rs
