library/std/src/env.rs

   1 //! Inspection and manipulation of the process's environment.
   2 //!
   3 //! This module contains functions to inspect various aspects such as
   4 //! environment variables, process arguments, the current directory, and various
   5 //! other important directories.
   6 //!
   7 //! There are several functions and structs in this module that have a
   8 //! counterpart ending in `os`. Those ending in `os` will return an [`OsString`]
   9 //! and those without will return a [`String`].
  10
  11 #![stable(feature = "env", since = "1.0.0")]
  12
  13 #[cfg(test)]
  14 mod tests;
  15
  16 use crate::error::Error;
  17 use crate::ffi::{OsStr, OsString};
  18 use crate::fmt;
  19 use crate::io;
  20 use crate::path::{Path, PathBuf};
  21 use crate::sys;
  22 use crate::sys::os as os_imp;
  23
  24 /// Returns the current working directory as a [`PathBuf`].
  25 ///
  26 /// # Errors
  27 ///
  28 /// Returns an [`Err`] if the current working directory value is invalid.
  29 /// Possible cases:
  30 ///
  31 /// * Current directory does not exist.
  32 /// * There are insufficient permissions to access the current directory.
  33 ///
  34 /// # Examples
  35 ///
  36 /// ```
  37 /// use std::env;
  38 ///
  39 /// fn main() -> std::io::Result<()> {
  40 ///     let path = env::current_dir()?;
  41 ///     println!("The current directory is {}", path.display());
  42 ///     Ok(())
  43 /// }
  44 /// ```
  45 #[stable(feature = "env", since = "1.0.0")]
  46 pub fn current_dir() -> io::Result<PathBuf> {
  47     os_imp::getcwd()
  48 }
  49
  50 /// Changes the current working directory to the specified path.
  51 ///
  52 /// Returns an [`Err`] if the operation fails.
  53 ///
  54 /// # Examples
  55 ///
  56 /// ```
  57 /// use std::env;
  58 /// use std::path::Path;
  59 ///
  60 /// let root = Path::new("/");
  61 /// assert!(env::set_current_dir(&root).is_ok());
  62 /// println!("Successfully changed working directory to {}!", root.display());
  63 /// ```
  64 #[stable(feature = "env", since = "1.0.0")]
  65 pub fn set_current_dir<P: AsRef<Path>>(path: P) -> io::Result<()> {
  66     os_imp::chdir(path.as_ref())
  67 }
  68
  69 /// An iterator over a snapshot of the environment variables of this process.
  70 ///
  71 /// This structure is created by [`env::vars()`]. See its documentation for more.
  72 ///
  73 /// [`env::vars()`]: vars
  74 #[stable(feature = "env", since = "1.0.0")]
  75 pub struct Vars {
  76     inner: VarsOs,
  77 }
  78
  79 /// An iterator over a snapshot of the environment variables of this process.
  80 ///
  81 /// This structure is created by [`env::vars_os()`]. See its documentation for more.
  82 ///
  83 /// [`env::vars_os()`]: vars_os
  84 #[stable(feature = "env", since = "1.0.0")]
  85 pub struct VarsOs {
  86     inner: os_imp::Env,
  87 }
  88
  89 /// Returns an iterator of (variable, value) pairs of strings, for all the
  90 /// environment variables of the current process.
  91 ///
  92 /// The returned iterator contains a snapshot of the process's environment
  93 /// variables at the time of this invocation. Modifications to environment
  94 /// variables afterwards will not be reflected in the returned iterator.
  95 ///
  96 /// # Panics
  97 ///
  98 /// While iterating, the returned iterator will panic if any key or value in the
  99 /// environment is not valid unicode. If this is not desired, consider using
 100 /// [`env::vars_os()`].
 101 ///
 102 /// # Examples
 103 ///
 104 /// ```
 105 /// use std::env;
 106 ///
 107 /// // We will iterate through the references to the element returned by
 108 /// // env::vars();
 109 /// for (key, value) in env::vars() {
 110 ///     println!("{}: {}", key, value);
 111 /// }
 112 /// ```
 113 ///
 114 /// [`env::vars_os()`]: vars_os
 115 #[stable(feature = "env", since = "1.0.0")]
 116 pub fn vars() -> Vars {
 117     Vars { inner: vars_os() }
 118 }
 119
 120 /// Returns an iterator of (variable, value) pairs of OS strings, for all the
 121 /// environment variables of the current process.
 122 ///
 123 /// The returned iterator contains a snapshot of the process's environment
 124 /// variables at the time of this invocation. Modifications to environment
 125 /// variables afterwards will not be reflected in the returned iterator.
 126 ///
 127 /// Note that the returned iterator will not check if the environment variables
 128 /// are valid Unicode. If you want to panic on invalid UTF-8,
 129 /// use the [`vars`] function instead.
 130 ///
 131 /// # Examples
 132 ///
 133 /// ```
 134 /// use std::env;
 135 ///
 136 /// // We will iterate through the references to the element returned by
 137 /// // env::vars_os();
 138 /// for (key, value) in env::vars_os() {
 139 ///     println!("{:?}: {:?}", key, value);
 140 /// }
 141 /// ```
 142 #[stable(feature = "env", since = "1.0.0")]
 143 pub fn vars_os() -> VarsOs {
 144     VarsOs { inner: os_imp::env() }
 145 }
 146
 147 #[stable(feature = "env", since = "1.0.0")]
 148 impl Iterator for Vars {
 149     type Item = (String, String);
 150     fn next(&mut self) -> Option<(String, String)> {
 151         self.inner.next().map(|(a, b)| (a.into_string().unwrap(), b.into_string().unwrap()))
 152     }
 153     fn size_hint(&self) -> (usize, Option<usize>) {
 154         self.inner.size_hint()
 155     }
 156 }
 157
 158 #[stable(feature = "std_debug", since = "1.16.0")]
 159 impl fmt::Debug for Vars {
 160     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 161         f.debug_struct("Vars").finish_non_exhaustive()
 162     }
 163 }
 164
 165 #[stable(feature = "env", since = "1.0.0")]
 166 impl Iterator for VarsOs {
 167     type Item = (OsString, OsString);
 168     fn next(&mut self) -> Option<(OsString, OsString)> {
 169         self.inner.next()
 170     }
 171     fn size_hint(&self) -> (usize, Option<usize>) {
 172         self.inner.size_hint()
 173     }
 174 }
 175
 176 #[stable(feature = "std_debug", since = "1.16.0")]
 177 impl fmt::Debug for VarsOs {
 178     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 179         f.debug_struct("VarOs").finish_non_exhaustive()
 180     }
 181 }
 182
 183 /// Fetches the environment variable `key` from the current process.
 184 ///
 185 /// # Errors
 186 ///
 187 /// Errors if the environment variable is not present.
 188 /// Errors if the environment variable is not valid Unicode. If this is not desired, consider using
 189 /// [`var_os`].
 190 ///
 191 /// # Panics
 192 ///
 193 /// This function may panic if `key` is empty, contains an ASCII equals sign
 194 /// `'='` or the NUL character `'\0'`, or when the value contains the NUL
 195 /// character.
 196 ///
 197 /// # Examples
 198 ///
 199 /// ```
 200 /// use std::env;
 201 ///
 202 /// let key = "HOME";
 203 /// match env::var(key) {
 204 ///     Ok(val) => println!("{}: {:?}", key, val),
 205 ///     Err(e) => println!("couldn't interpret {}: {}", key, e),
 206 /// }
 207 /// ```
 208 #[stable(feature = "env", since = "1.0.0")]
 209 pub fn var<K: AsRef<OsStr>>(key: K) -> Result<String, VarError> {
 210     _var(key.as_ref())
 211 }
 212
 213 fn _var(key: &OsStr) -> Result<String, VarError> {
 214     match var_os(key) {
 215         Some(s) => s.into_string().map_err(VarError::NotUnicode),
 216         None => Err(VarError::NotPresent),
 217     }
 218 }
 219
 220 /// Fetches the environment variable `key` from the current process, returning
 221 /// [`None`] if the variable isn't set.
 222 ///
 223 /// # Panics
 224 ///
 225 /// This function may panic if `key` is empty, contains an ASCII equals sign
 226 /// `'='` or the NUL character `'\0'`, or when the value contains the NUL
 227 /// character.
 228 ///
 229 /// Note that the method will not check if the environment variable
 230 /// is valid Unicode. If you want to have an error on invalid UTF-8,
 231 /// use the [`var`] function instead.
 232 ///
 233 /// # Examples
 234 ///
 235 /// ```
 236 /// use std::env;
 237 ///
 238 /// let key = "HOME";
 239 /// match env::var_os(key) {
 240 ///     Some(val) => println!("{}: {:?}", key, val),
 241 ///     None => println!("{} is not defined in the environment.", key)
 242 /// }
 243 /// ```
 244 #[stable(feature = "env", since = "1.0.0")]
 245 pub fn var_os<K: AsRef<OsStr>>(key: K) -> Option<OsString> {
 246     _var_os(key.as_ref())
 247 }
 248
 249 fn _var_os(key: &OsStr) -> Option<OsString> {
 250     os_imp::getenv(key)
 251         .unwrap_or_else(|e| panic!("failed to get environment variable `{:?}`: {}", key, e))
 252 }
 253
 254 /// The error type for operations interacting with environment variables.
 255 /// Possibly returned from [`env::var()`].
 256 ///
 257 /// [`env::var()`]: var
 258 #[derive(Debug, PartialEq, Eq, Clone)]
 259 #[stable(feature = "env", since = "1.0.0")]
 260 pub enum VarError {
 261     /// The specified environment variable was not present in the current
 262     /// process's environment.
 263     #[stable(feature = "env", since = "1.0.0")]
 264     NotPresent,
 265
 266     /// The specified environment variable was found, but it did not contain
 267     /// valid unicode data. The found data is returned as a payload of this
 268     /// variant.
 269     #[stable(feature = "env", since = "1.0.0")]
 270     NotUnicode(#[stable(feature = "env", since = "1.0.0")] OsString),
 271 }
 272
 273 #[stable(feature = "env", since = "1.0.0")]
 274 impl fmt::Display for VarError {
 275     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 276         match *self {
 277             VarError::NotPresent => write!(f, "environment variable not found"),
 278             VarError::NotUnicode(ref s) => {
 279                 write!(f, "environment variable was not valid unicode: {:?}", s)
 280             }
 281         }
 282     }
 283 }
 284
 285 #[stable(feature = "env", since = "1.0.0")]
 286 impl Error for VarError {
 287     #[allow(deprecated)]
 288     fn description(&self) -> &str {
 289         match *self {
 290             VarError::NotPresent => "environment variable not found",
 291             VarError::NotUnicode(..) => "environment variable was not valid unicode",
 292         }
 293     }
 294 }
 295
 296 /// Sets the environment variable `k` to the value `v` for the currently running
 297 /// process.
 298 ///
 299 /// Note that while concurrent access to environment variables is safe in Rust,
 300 /// some platforms only expose inherently unsafe non-threadsafe APIs for
 301 /// inspecting the environment. As a result, extra care needs to be taken when
 302 /// auditing calls to unsafe external FFI functions to ensure that any external
 303 /// environment accesses are properly synchronized with accesses in Rust.
 304 ///
 305 /// Discussion of this unsafety on Unix may be found in:
 306 ///
 307 ///  - [Austin Group Bugzilla](http://austingroupbugs.net/view.php?id=188)
 308 ///  - [GNU C library Bugzilla](https://sourceware.org/bugzilla/show_bug.cgi?id=15607#c2)
 309 ///
 310 /// # Panics
 311 ///
 312 /// This function may panic if `key` is empty, contains an ASCII equals sign
 313 /// `'='` or the NUL character `'\0'`, or when the value contains the NUL
 314 /// character.
 315 ///
 316 /// # Examples
 317 ///
 318 /// ```
 319 /// use std::env;
 320 ///
 321 /// let key = "KEY";
 322 /// env::set_var(key, "VALUE");
 323 /// assert_eq!(env::var(key), Ok("VALUE".to_string()));
 324 /// ```
 325 #[stable(feature = "env", since = "1.0.0")]
 326 pub fn set_var<K: AsRef<OsStr>, V: AsRef<OsStr>>(k: K, v: V) {
 327     _set_var(k.as_ref(), v.as_ref())
 328 }
 329
 330 fn _set_var(k: &OsStr, v: &OsStr) {
 331     os_imp::setenv(k, v).unwrap_or_else(|e| {
 332         panic!("failed to set environment variable `{:?}` to `{:?}`: {}", k, v, e)
 333     })
 334 }
 335
 336 /// Removes an environment variable from the environment of the currently running process.
 337 ///
 338 /// Note that while concurrent access to environment variables is safe in Rust,
 339 /// some platforms only expose inherently unsafe non-threadsafe APIs for
 340 /// inspecting the environment. As a result extra care needs to be taken when
 341 /// auditing calls to unsafe external FFI functions to ensure that any external
 342 /// environment accesses are properly synchronized with accesses in Rust.
 343 ///
 344 /// Discussion of this unsafety on Unix may be found in:
 345 ///
 346 ///  - [Austin Group Bugzilla](http://austingroupbugs.net/view.php?id=188)
 347 ///  - [GNU C library Bugzilla](https://sourceware.org/bugzilla/show_bug.cgi?id=15607#c2)
 348 ///
 349 /// # Panics
 350 ///
 351 /// This function may panic if `key` is empty, contains an ASCII equals sign
 352 /// `'='` or the NUL character `'\0'`, or when the value contains the NUL
 353 /// character.
 354 ///
 355 /// # Examples
 356 ///
 357 /// ```
 358 /// use std::env;
 359 ///
 360 /// let key = "KEY";
 361 /// env::set_var(key, "VALUE");
 362 /// assert_eq!(env::var(key), Ok("VALUE".to_string()));
 363 ///
 364 /// env::remove_var(key);
 365 /// assert!(env::var(key).is_err());
 366 /// ```
 367 #[stable(feature = "env", since = "1.0.0")]
 368 pub fn remove_var<K: AsRef<OsStr>>(k: K) {
 369     _remove_var(k.as_ref())
 370 }
 371
 372 fn _remove_var(k: &OsStr) {
 373     os_imp::unsetenv(k)
 374         .unwrap_or_else(|e| panic!("failed to remove environment variable `{:?}`: {}", k, e))
 375 }
 376
 377 /// An iterator that splits an environment variable into paths according to
 378 /// platform-specific conventions.
 379 ///
 380 /// The iterator element type is [`PathBuf`].
 381 ///
 382 /// This structure is created by [`env::split_paths()`]. See its
 383 /// documentation for more.
 384 ///
 385 /// [`env::split_paths()`]: split_paths
 386 #[stable(feature = "env", since = "1.0.0")]
 387 pub struct SplitPaths<'a> {
 388     inner: os_imp::SplitPaths<'a>,
 389 }
 390
 391 /// Parses input according to platform conventions for the `PATH`
 392 /// environment variable.
 393 ///
 394 /// Returns an iterator over the paths contained in `unparsed`. The iterator
 395 /// element type is [`PathBuf`].
 396 ///
 397 /// # Examples
 398 ///
 399 /// ```
 400 /// use std::env;
 401 ///
 402 /// let key = "PATH";
 403 /// match env::var_os(key) {
 404 ///     Some(paths) => {
 405 ///         for path in env::split_paths(&paths) {
 406 ///             println!("'{}'", path.display());
 407 ///         }
 408 ///     }
 409 ///     None => println!("{} is not defined in the environment.", key)
 410 /// }
 411 /// ```
 412 #[stable(feature = "env", since = "1.0.0")]
 413 pub fn split_paths<T: AsRef<OsStr> + ?Sized>(unparsed: &T) -> SplitPaths<'_> {
 414     SplitPaths { inner: os_imp::split_paths(unparsed.as_ref()) }
 415 }
 416
 417 #[stable(feature = "env", since = "1.0.0")]
 418 impl<'a> Iterator for SplitPaths<'a> {
 419     type Item = PathBuf;
 420     fn next(&mut self) -> Option<PathBuf> {
 421         self.inner.next()
 422     }
 423     fn size_hint(&self) -> (usize, Option<usize>) {
 424         self.inner.size_hint()
 425     }
 426 }
 427
 428 #[stable(feature = "std_debug", since = "1.16.0")]
 429 impl fmt::Debug for SplitPaths<'_> {
 430     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 431         f.debug_struct("SplitPaths").finish_non_exhaustive()
 432     }
 433 }
 434
 435 /// The error type for operations on the `PATH` variable. Possibly returned from
 436 /// [`env::join_paths()`].
 437 ///
 438 /// [`env::join_paths()`]: join_paths
 439 #[derive(Debug)]
 440 #[stable(feature = "env", since = "1.0.0")]
 441 pub struct JoinPathsError {
 442     inner: os_imp::JoinPathsError,
 443 }
 444
 445 /// Joins a collection of [`Path`]s appropriately for the `PATH`
 446 /// environment variable.
 447 ///
 448 /// # Errors
 449 ///
 450 /// Returns an [`Err`] (containing an error message) if one of the input
 451 /// [`Path`]s contains an invalid character for constructing the `PATH`
 452 /// variable (a double quote on Windows or a colon on Unix).
 453 ///
 454 /// # Examples
 455 ///
 456 /// Joining paths on a Unix-like platform:
 457 ///
 458 /// ```
 459 /// use std::env;
 460 /// use std::ffi::OsString;
 461 /// use std::path::Path;
 462 ///
 463 /// fn main() -> Result<(), env::JoinPathsError> {
 464 /// # if cfg!(unix) {
 465 ///     let paths = [Path::new("/bin"), Path::new("/usr/bin")];
 466 ///     let path_os_string = env::join_paths(paths.iter())?;
 467 ///     assert_eq!(path_os_string, OsString::from("/bin:/usr/bin"));
 468 /// # }
 469 ///     Ok(())
 470 /// }
 471 /// ```
 472 ///
 473 /// Joining a path containing a colon on a Unix-like platform results in an
 474 /// error:
 475 ///
 476 /// ```
 477 /// # if cfg!(unix) {
 478 /// use std::env;
 479 /// use std::path::Path;
 480 ///
 481 /// let paths = [Path::new("/bin"), Path::new("/usr/bi:n")];
 482 /// assert!(env::join_paths(paths.iter()).is_err());
 483 /// # }
 484 /// ```
 485 ///
 486 /// Using `env::join_paths()` with [`env::split_paths()`] to append an item to
 487 /// the `PATH` environment variable:
 488 ///
 489 /// ```
 490 /// use std::env;
 491 /// use std::path::PathBuf;
 492 ///
 493 /// fn main() -> Result<(), env::JoinPathsError> {
 494 ///     if let Some(path) = env::var_os("PATH") {
 495 ///         let mut paths = env::split_paths(&path).collect::<Vec<_>>();
 496 ///         paths.push(PathBuf::from("/home/xyz/bin"));
 497 ///         let new_path = env::join_paths(paths)?;
 498 ///         env::set_var("PATH", &new_path);
 499 ///     }
 500 ///
 501 ///     Ok(())
 502 /// }
 503 /// ```
 504 ///
 505 /// [`env::split_paths()`]: split_paths
 506 #[stable(feature = "env", since = "1.0.0")]
 507 pub fn join_paths<I, T>(paths: I) -> Result<OsString, JoinPathsError>
 508 where
 509     I: IntoIterator<Item = T>,
 510     T: AsRef<OsStr>,
 511 {
 512     os_imp::join_paths(paths.into_iter()).map_err(|e| JoinPathsError { inner: e })
 513 }
 514
 515 #[stable(feature = "env", since = "1.0.0")]
 516 impl fmt::Display for JoinPathsError {
 517     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 518         self.inner.fmt(f)
 519     }
 520 }
 521
 522 #[stable(feature = "env", since = "1.0.0")]
 523 impl Error for JoinPathsError {
 524     #[allow(deprecated, deprecated_in_future)]
 525     fn description(&self) -> &str {
 526         self.inner.description()
 527     }
 528 }
 529
 530 /// Returns the path of the current user's home directory if known.
 531 ///
 532 /// # Unix
 533 ///
 534 /// - Returns the value of the 'HOME' environment variable if it is set
 535 ///   (including to an empty string).
 536 /// - Otherwise, it tries to determine the home directory by invoking the `getpwuid_r` function
 537 ///   using the UID of the current user. An empty home directory field returned from the
 538 ///   `getpwuid_r` function is considered to be a valid value.
 539 /// - Returns `None` if the current user has no entry in the /etc/passwd file.
 540 ///
 541 /// # Windows
 542 ///
 543 /// - Returns the value of the 'HOME' environment variable if it is set
 544 ///   (including to an empty string).
 545 /// - Otherwise, returns the value of the 'USERPROFILE' environment variable if it is set
 546 ///   (including to an empty string).
 547 /// - If both do not exist, [`GetUserProfileDirectory`][msdn] is used to return the path.
 548 ///
 549 /// [msdn]: https://docs.microsoft.com/en-us/windows/win32/api/userenv/nf-userenv-getuserprofiledirectorya
 550 ///
 551 /// # Examples
 552 ///
 553 /// ```
 554 /// use std::env;
 555 ///
 556 /// match env::home_dir() {
 557 ///     Some(path) => println!("Your home directory, probably: {}", path.display()),
 558 ///     None => println!("Impossible to get your home dir!"),
 559 /// }
 560 /// ```
 561 #[rustc_deprecated(
 562     since = "1.29.0",
 563     reason = "This function's behavior is unexpected and probably not what you want. \
 564               Consider using a crate from crates.io instead."
 565 )]
 566 #[stable(feature = "env", since = "1.0.0")]
 567 pub fn home_dir() -> Option<PathBuf> {
 568     os_imp::home_dir()
 569 }
 570
 571 /// Returns the path of a temporary directory.
 572 ///
 573 /// The temporary directory may be shared among users, or between processes
 574 /// with different privileges; thus, the creation of any files or directories
 575 /// in the temporary directory must use a secure method to create a uniquely
 576 /// named file. Creating a file or directory with a fixed or predictable name
 577 /// may result in "insecure temporary file" security vulnerabilities. Consider
 578 /// using a crate that securely creates temporary files or directories.
 579 ///
 580 /// # Unix
 581 ///
 582 /// Returns the value of the `TMPDIR` environment variable if it is
 583 /// set, otherwise for non-Android it returns `/tmp`. If Android, since there
 584 /// is no global temporary folder (it is usually allocated per-app), it returns
 585 /// `/data/local/tmp`.
 586 ///
 587 /// # Windows
 588 ///
 589 /// Returns the value of, in order, the `TMP`, `TEMP`,
 590 /// `USERPROFILE` environment variable if any are set and not the empty
 591 /// string. Otherwise, `temp_dir` returns the path of the Windows directory.
 592 /// This behavior is identical to that of [`GetTempPath`][msdn], which this
 593 /// function uses internally.
 594 ///
 595 /// [msdn]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-gettemppatha
 596 ///
 597 /// ```no_run
 598 /// use std::env;
 599 ///
 600 /// fn main() {
 601 ///     let mut dir = env::temp_dir();
 602 ///     println!("Temporary directory: {}", dir.display());
 603 /// }
 604 /// ```
 605 #[stable(feature = "env", since = "1.0.0")]
 606 pub fn temp_dir() -> PathBuf {
 607     os_imp::temp_dir()
 608 }
 609
 610 /// Returns the full filesystem path of the current running executable.
 611 ///
 612 /// # Platform-specific behavior
 613 ///
 614 /// If the executable was invoked through a symbolic link, some platforms will
 615 /// return the path of the symbolic link and other platforms will return the
 616 /// path of the symbolic link’s target.
 617 ///
 618 /// # Errors
 619 ///
 620 /// Acquiring the path of the current executable is a platform-specific operation
 621 /// that can fail for a good number of reasons. Some errors can include, but not
 622 /// be limited to, filesystem operations failing or general syscall failures.
 623 ///
 624 /// # Security
 625 ///
 626 /// The output of this function should not be used in anything that might have
 627 /// security implications. For example:
 628 ///
 629 /// ```
 630 /// fn main() {
 631 ///     println!("{:?}", std::env::current_exe());
 632 /// }
 633 /// ```
 634 ///
 635 /// On Linux systems, if this is compiled as `foo`:
 636 ///
 637 /// ```bash
 638 /// $ rustc foo.rs
 639 /// $ ./foo
 640 /// Ok("/home/alex/foo")
 641 /// ```
 642 ///
 643 /// And you make a hard link of the program:
 644 ///
 645 /// ```bash
 646 /// $ ln foo bar
 647 /// ```
 648 ///
 649 /// When you run it, you won’t get the path of the original executable, you’ll
 650 /// get the path of the hard link:
 651 ///
 652 /// ```bash
 653 /// $ ./bar
 654 /// Ok("/home/alex/bar")
 655 /// ```
 656 ///
 657 /// This sort of behavior has been known to [lead to privilege escalation] when
 658 /// used incorrectly.
 659 ///
 660 /// [lead to privilege escalation]: https://securityvulns.com/Wdocument183.html
 661 ///
 662 /// # Examples
 663 ///
 664 /// ```
 665 /// use std::env;
 666 ///
 667 /// match env::current_exe() {
 668 ///     Ok(exe_path) => println!("Path of this executable is: {}",
 669 ///                              exe_path.display()),
 670 ///     Err(e) => println!("failed to get current exe path: {}", e),
 671 /// };
 672 /// ```
 673 #[stable(feature = "env", since = "1.0.0")]
 674 pub fn current_exe() -> io::Result<PathBuf> {
 675     os_imp::current_exe()
 676 }
 677
 678 /// An iterator over the arguments of a process, yielding a [`String`] value for
 679 /// each argument.
 680 ///
 681 /// This struct is created by [`env::args()`]. See its documentation
 682 /// for more.
 683 ///
 684 /// The first element is traditionally the path of the executable, but it can be
 685 /// set to arbitrary text, and may not even exist. This means this property
 686 /// should not be relied upon for security purposes.
 687 ///
 688 /// [`env::args()`]: args
 689 #[stable(feature = "env", since = "1.0.0")]
 690 pub struct Args {
 691     inner: ArgsOs,
 692 }
 693
 694 /// An iterator over the arguments of a process, yielding an [`OsString`] value
 695 /// for each argument.
 696 ///
 697 /// This struct is created by [`env::args_os()`]. See its documentation
 698 /// for more.
 699 ///
 700 /// The first element is traditionally the path of the executable, but it can be
 701 /// set to arbitrary text, and may not even exist. This means this property
 702 /// should not be relied upon for security purposes.
 703 ///
 704 /// [`env::args_os()`]: args_os
 705 #[stable(feature = "env", since = "1.0.0")]
 706 pub struct ArgsOs {
 707     inner: sys::args::Args,
 708 }
 709
 710 /// Returns the arguments that this program was started with (normally passed
 711 /// via the command line).
 712 ///
 713 /// The first element is traditionally the path of the executable, but it can be
 714 /// set to arbitrary text, and may not even exist. This means this property should
 715 /// not be relied upon for security purposes.
 716 ///
 717 /// On Unix systems the shell usually expands unquoted arguments with glob patterns
 718 /// (such as `*` and `?`). On Windows this is not done, and such arguments are
 719 /// passed as-is.
 720 ///
 721 /// On glibc Linux systems, arguments are retrieved by placing a function in `.init_array`.
 722 /// glibc passes `argc`, `argv`, and `envp` to functions in `.init_array`, as a non-standard
 723 /// extension. This allows `std::env::args` to work even in a `cdylib` or `staticlib`, as it
 724 /// does on macOS and Windows.
 725 ///
 726 /// # Panics
 727 ///
 728 /// The returned iterator will panic during iteration if any argument to the
 729 /// process is not valid Unicode. If this is not desired,
 730 /// use the [`args_os`] function instead.
 731 ///
 732 /// # Examples
 733 ///
 734 /// ```
 735 /// use std::env;
 736 ///
 737 /// // Prints each argument on a separate line
 738 /// for argument in env::args() {
 739 ///     println!("{}", argument);
 740 /// }
 741 /// ```
 742 #[stable(feature = "env", since = "1.0.0")]
 743 pub fn args() -> Args {
 744     Args { inner: args_os() }
 745 }
 746
 747 /// Returns the arguments that this program was started with (normally passed
 748 /// via the command line).
 749 ///
 750 /// The first element is traditionally the path of the executable, but it can be
 751 /// set to arbitrary text, and may not even exist. This means this property should
 752 /// not be relied upon for security purposes.
 753 ///
 754 /// On Unix systems the shell usually expands unquoted arguments with glob patterns
 755 /// (such as `*` and `?`). On Windows this is not done, and such arguments are
 756 /// passed as-is.
 757 ///
 758 /// On glibc Linux systems, arguments are retrieved by placing a function in `.init_array`.
 759 /// glibc passes `argc`, `argv`, and `envp` to functions in `.init_array`, as a non-standard
 760 /// extension. This allows `std::env::args_os` to work even in a `cdylib` or `staticlib`, as it
 761 /// does on macOS and Windows.
 762 ///
 763 /// Note that the returned iterator will not check if the arguments to the
 764 /// process are valid Unicode. If you want to panic on invalid UTF-8,
 765 /// use the [`args`] function instead.
 766 ///
 767 /// # Examples
 768 ///
 769 /// ```
 770 /// use std::env;
 771 ///
 772 /// // Prints each argument on a separate line
 773 /// for argument in env::args_os() {
 774 ///     println!("{:?}", argument);
 775 /// }
 776 /// ```
 777 #[stable(feature = "env", since = "1.0.0")]
 778 pub fn args_os() -> ArgsOs {
 779     ArgsOs { inner: sys::args::args() }
 780 }
 781
 782 #[stable(feature = "env_unimpl_send_sync", since = "1.26.0")]
 783 impl !Send for Args {}
 784
 785 #[stable(feature = "env_unimpl_send_sync", since = "1.26.0")]
 786 impl !Sync for Args {}
 787
 788 #[stable(feature = "env", since = "1.0.0")]
 789 impl Iterator for Args {
 790     type Item = String;
 791     fn next(&mut self) -> Option<String> {
 792         self.inner.next().map(|s| s.into_string().unwrap())
 793     }
 794     fn size_hint(&self) -> (usize, Option<usize>) {
 795         self.inner.size_hint()
 796     }
 797 }
 798
 799 #[stable(feature = "env", since = "1.0.0")]
 800 impl ExactSizeIterator for Args {
 801     fn len(&self) -> usize {
 802         self.inner.len()
 803     }
 804     fn is_empty(&self) -> bool {
 805         self.inner.is_empty()
 806     }
 807 }
 808
 809 #[stable(feature = "env_iterators", since = "1.12.0")]
 810 impl DoubleEndedIterator for Args {
 811     fn next_back(&mut self) -> Option<String> {
 812         self.inner.next_back().map(|s| s.into_string().unwrap())
 813     }
 814 }
 815
 816 #[stable(feature = "std_debug", since = "1.16.0")]
 817 impl fmt::Debug for Args {
 818     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 819         f.debug_struct("Args").field("inner", &self.inner.inner).finish()
 820     }
 821 }
 822
 823 #[stable(feature = "env_unimpl_send_sync", since = "1.26.0")]
 824 impl !Send for ArgsOs {}
 825
 826 #[stable(feature = "env_unimpl_send_sync", since = "1.26.0")]
 827 impl !Sync for ArgsOs {}
 828
 829 #[stable(feature = "env", since = "1.0.0")]
 830 impl Iterator for ArgsOs {
 831     type Item = OsString;
 832     fn next(&mut self) -> Option<OsString> {
 833         self.inner.next()
 834     }
 835     fn size_hint(&self) -> (usize, Option<usize>) {
 836         self.inner.size_hint()
 837     }
 838 }
 839
 840 #[stable(feature = "env", since = "1.0.0")]
 841 impl ExactSizeIterator for ArgsOs {
 842     fn len(&self) -> usize {
 843         self.inner.len()
 844     }
 845     fn is_empty(&self) -> bool {
 846         self.inner.is_empty()
 847     }
 848 }
 849
 850 #[stable(feature = "env_iterators", since = "1.12.0")]
 851 impl DoubleEndedIterator for ArgsOs {
 852     fn next_back(&mut self) -> Option<OsString> {
 853         self.inner.next_back()
 854     }
 855 }
 856
 857 #[stable(feature = "std_debug", since = "1.16.0")]
 858 impl fmt::Debug for ArgsOs {
 859     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 860         f.debug_struct("ArgsOs").field("inner", &self.inner).finish()
 861     }
 862 }
 863
 864 /// Constants associated with the current target
 865 #[stable(feature = "env", since = "1.0.0")]
 866 pub mod consts {
 867     use crate::sys::env::os;
 868
 869     /// A string describing the architecture of the CPU that is currently
 870     /// in use.
 871     ///
 872     /// Some possible values:
 873     ///
 874     /// - x86
 875     /// - x86_64
 876     /// - arm
 877     /// - aarch64
 878     /// - mips
 879     /// - mips64
 880     /// - powerpc
 881     /// - powerpc64
 882     /// - riscv64
 883     /// - s390x
 884     /// - sparc64
 885     #[stable(feature = "env", since = "1.0.0")]
 886     pub const ARCH: &str = env!("STD_ENV_ARCH");
 887
 888     /// The family of the operating system. Example value is `unix`.
 889     ///
 890     /// Some possible values:
 891     ///
 892     /// - unix
 893     /// - windows
 894     #[stable(feature = "env", since = "1.0.0")]
 895     pub const FAMILY: &str = os::FAMILY;
 896
 897     /// A string describing the specific operating system in use.
 898     /// Example value is `linux`.
 899     ///
 900     /// Some possible values:
 901     ///
 902     /// - linux
 903     /// - macos
 904     /// - ios
 905     /// - freebsd
 906     /// - dragonfly
 907     /// - netbsd
 908     /// - openbsd
 909     /// - solaris
 910     /// - android
 911     /// - windows
 912     #[stable(feature = "env", since = "1.0.0")]
 913     pub const OS: &str = os::OS;
 914
 915     /// Specifies the filename prefix used for shared libraries on this
 916     /// platform. Example value is `lib`.
 917     ///
 918     /// Some possible values:
 919     ///
 920     /// - lib
 921     /// - `""` (an empty string)
 922     #[stable(feature = "env", since = "1.0.0")]
 923     pub const DLL_PREFIX: &str = os::DLL_PREFIX;
 924
 925     /// Specifies the filename suffix used for shared libraries on this
 926     /// platform. Example value is `.so`.
 927     ///
 928     /// Some possible values:
 929     ///
 930     /// - .so
 931     /// - .dylib
 932     /// - .dll
 933     #[stable(feature = "env", since = "1.0.0")]
 934     pub const DLL_SUFFIX: &str = os::DLL_SUFFIX;
 935
 936     /// Specifies the file extension used for shared libraries on this
 937     /// platform that goes after the dot. Example value is `so`.
 938     ///
 939     /// Some possible values:
 940     ///
 941     /// - so
 942     /// - dylib
 943     /// - dll
 944     #[stable(feature = "env", since = "1.0.0")]
 945     pub const DLL_EXTENSION: &str = os::DLL_EXTENSION;
 946
 947     /// Specifies the filename suffix used for executable binaries on this
 948     /// platform. Example value is `.exe`.
 949     ///
 950     /// Some possible values:
 951     ///
 952     /// - .exe
 953     /// - .nexe
 954     /// - .pexe
 955     /// - `""` (an empty string)
 956     #[stable(feature = "env", since = "1.0.0")]
 957     pub const EXE_SUFFIX: &str = os::EXE_SUFFIX;
 958
 959     /// Specifies the file extension, if any, used for executable binaries
 960     /// on this platform. Example value is `exe`.
 961     ///
 962     /// Some possible values:
 963     ///
 964     /// - exe
 965     /// - `""` (an empty string)
 966     #[stable(feature = "env", since = "1.0.0")]
 967     pub const EXE_EXTENSION: &str = os::EXE_EXTENSION;
 968 }