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#![deny(missing_docs)] //! Utility for running a command in a subprocess. //! //! The [`Command`] type is a wrapper around the [`std::process::Command`] //! type that adds a few convenient features: //! //! - Print or log the command before running it //! - Optionally return an error if the command is not successful //! - The command can be formatted as a command-line string //! - The [`Command`] type can be cloned and its fields are public //! //! [`Command`]: struct.Command.html //! [`std::process::Command`]: https://doc.rust-lang.org/std/process/struct.Command.html use std::borrow::Cow; use std::collections::HashMap; use std::ffi::{OsStr, OsString}; use std::io::Read; use std::os::unix::ffi::OsStrExt; use std::path::PathBuf; use std::{fmt, io, process}; /// Type of error. #[derive(Debug)] pub enum ErrorKind { /// An error occurred in the calls used to run the command. For /// example, this variant is used if the program does not exist. Run(io::Error), /// The command exited non-zero or due to a signal. Exit(process::ExitStatus), } /// Error returned by [`Command::run`]. /// /// [`Command::run`]: struct.Command.html#method.run #[derive(Debug)] pub struct Error { /// The command that caused the error. pub command: Command, /// The type of error. pub kind: ErrorKind, } impl Error { /// Check if the error kind is `Run`. pub fn is_run_error(&self) -> bool { matches!(self.kind, ErrorKind::Run(_)) } /// Check if the error kind is `Exit`. pub fn is_exit_error(&self) -> bool { matches!(self.kind, ErrorKind::Exit(_)) } } /// Internal trait for converting an io::Error to an Error. trait IntoError<T> { fn into_run_error(self, command: &Command) -> Result<T, Error>; } impl<T> IntoError<T> for Result<T, io::Error> { fn into_run_error(self, command: &Command) -> Result<T, Error> { self.map_err(|err| Error { command: command.clone(), kind: ErrorKind::Run(err), }) } } impl fmt::Display for Error { fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> { match &self.kind { ErrorKind::Run(err) => write!( f, "failed to run '{}': {}", self.command.command_line_lossy(), err ), ErrorKind::Exit(err) => write!( f, "command '{}' failed: {}", self.command.command_line_lossy(), err ), } } } impl std::error::Error for Error {} /// The output of a finished process. #[derive(Clone, Debug, Eq, PartialEq)] pub struct Output { /// The status (exit code) of the process. pub status: process::ExitStatus, /// The data that the process wrote to stdout. pub stdout: Vec<u8>, /// The data that the process wrote to stderr. pub stderr: Vec<u8>, } impl Output { /// Get stdout as a string. pub fn stdout_string_lossy(&self) -> Cow<str> { String::from_utf8_lossy(&self.stdout) } /// Get stderr as a string. pub fn stderr_string_lossy(&self) -> Cow<str> { String::from_utf8_lossy(&self.stderr) } } impl From<process::Output> for Output { fn from(o: process::Output) -> Output { Output { status: o.status, stdout: o.stdout, stderr: o.stderr, } } } fn combine_output(mut cmd: process::Command) -> Result<Output, io::Error> { let (mut reader, writer) = os_pipe::pipe()?; let writer_clone = writer.try_clone()?; cmd.stdout(writer); cmd.stderr(writer_clone); let mut handle = cmd.spawn()?; drop(cmd); let mut output = Vec::new(); reader.read_to_end(&mut output)?; let status = handle.wait()?; Ok(Output { stdout: output, stderr: Vec::new(), status, }) } /// Where log messages go. #[derive(Clone, Copy, Debug, Eq, PartialEq)] pub enum LogTo { /// Print to stdout. Stdout, /// Use the standard `log` crate. #[cfg(feature = "logging")] Log, } /// A command to run in a subprocess and options for how it is run. /// /// Some notable trait implementations: /// - Derives `Clone`, `Debug`, `Eq`, and `PartialEq` /// - `Default` (see docstrings for each field for what the /// corresponding default is) /// - `From<&Command> for std::process::Command` to convert to a /// [`std::process::Command`] /// /// [`std::process::Command`]: https://doc.rust-lang.org/std/process/struct.Command.html #[derive(Clone, Debug, Eq, PartialEq)] pub struct Command { /// Program path. /// /// The path can be just a file name, in which case the `$PATH` is /// searched. pub program: PathBuf, /// Arguments passed to the program. pub args: Vec<OsString>, /// Directory from which to run the program. /// /// If not set (the default), the current working directory is /// used. pub dir: Option<PathBuf>, /// Where log messages go. The default is stdout. pub log_to: LogTo, /// If `true` (the default), log the command before running it. pub log_command: bool, /// If `true`, log the output if the command exits non-zero or due /// to a signal. This does nothing is `capture` is `false` or if /// `check` is `false`. The default is `false`. pub log_output_on_error: bool, /// If `true` (the default), check if the command exited /// successfully and return an error if not. pub check: bool, /// If `true`, capture the stdout and stderr of the /// command. The default is `false`. pub capture: bool, /// If `true`, send stderr to stdout; the `stderr` field in /// `Output` will be empty. The default is `false.` pub combine_output: bool, /// If `false` (the default), inherit environment variables from the /// current process. pub clear_env: bool, /// Add or update environment variables in the child process. pub env: HashMap<OsString, OsString>, } impl Command { /// Make a new Command with the given program. /// /// All other fields are set to the defaults. pub fn new<S: AsRef<OsStr>>(program: S) -> Command { Command { program: program.as_ref().into(), ..Default::default() } } /// Make a new Command with the given program and args. /// /// All other fields are set to the defaults. pub fn with_args<I, S1, S2>(program: S1, args: I) -> Command where S1: AsRef<OsStr>, S2: AsRef<OsStr>, I: IntoIterator<Item = S2>, { Command { program: program.as_ref().into(), args: args.into_iter().map(|arg| arg.as_ref().into()).collect(), ..Default::default() } } /// Append a single argument. pub fn add_arg<S: AsRef<OsStr>>(&mut self, arg: S) -> &mut Self { self.args.push(arg.as_ref().into()); self } /// Append two arguments. /// /// This is equivalent to calling `add_arg` twice; it is for the /// common case where the arguments have different types, e.g. a /// literal string for the first argument and a `Path` for the /// second argument. pub fn add_arg_pair<S1, S2>(&mut self, arg1: S1, arg2: S2) -> &mut Self where S1: AsRef<OsStr>, S2: AsRef<OsStr>, { self.add_arg(arg1); self.add_arg(arg2); self } /// Append multiple arguments. pub fn add_args<I, S>(&mut self, args: I) -> &mut Self where S: AsRef<OsStr>, I: IntoIterator<Item = S>, { for arg in args { self.add_arg(arg); } self } /// Set `capture` to `true`. pub fn enable_capture(&mut self) -> &mut Self { self.capture = true; self } /// Set `combine_output` to `true`. pub fn combine_output(&mut self) -> &mut Self { self.combine_output = true; self } /// Set the directory from which to run the program. pub fn set_dir<S: AsRef<OsStr>>(&mut self, dir: S) -> &mut Self { self.dir = Some(dir.as_ref().into()); self } /// Set `check` to `false`. pub fn disable_check(&mut self) -> &mut Self { self.check = false; self } /// Run the command. /// /// If `capture` is `true`, the command's output (stdout and /// stderr) is returned along with the status. If not, the stdout /// and stderr are empty. /// /// If the command fails to start an error is returned. If check /// is set, an error is also returned if the command exits /// non-zero or due to a signal. /// /// If `log_command` is `true` then the command line is logged /// before running it. If the command fails the error is not /// logged or printed, but the resulting error type implements /// `Display` and can be used for this purpose. pub fn run(&self) -> Result<Output, Error> { let cmd_str = self.command_line_lossy(); if self.log_command { match self.log_to { LogTo::Stdout => println!("{}", cmd_str), #[cfg(feature = "logging")] LogTo::Log => log::info!("{}", cmd_str), } } let mut cmd: process::Command = self.into(); let out = if self.capture { if self.combine_output { combine_output(cmd).into_run_error(self)? } else { cmd.output().into_run_error(self)?.into() } } else { let status = cmd.status().into_run_error(self)?; Output { stdout: Vec::new(), stderr: Vec::new(), status, } }; if self.check && !out.status.success() { if self.capture && self.log_output_on_error { let mut msg = format!("command '{}' failed: {}", cmd_str, out.status); if self.combine_output { msg = format!( "{}\noutput:\n{}", msg, out.stdout_string_lossy() ); } else { msg = format!( "{}\nstdout:\n{}\nstderr:\n{}", msg, out.stdout_string_lossy(), out.stderr_string_lossy() ); } match self.log_to { LogTo::Stdout => println!("{}", msg), #[cfg(feature = "logging")] LogTo::Log => log::error!("{}", msg), } } return Err(Error { command: self.clone(), kind: ErrorKind::Exit(out.status), }); } Ok(out) } /// Format as a space-separated command line. /// /// The program path and the arguments are converted to strings /// with [`String::from_utf8_lossy`]. /// /// If any component contains characters that are not ASCII /// alphanumeric or in the set `/-,:.=`, the component is /// quoted with `'` (single quotes). This is both too aggressive /// (unnecessarily quoting things that don't need to be quoted) /// and incorrect (e.g. a single quote will itself be quoted with /// a single quote). This method is mostly intended for logging /// though, and it should work reasonably well for that. /// /// [`String::from_utf8_lossy`]: https://doc.rust-lang.org/std/string/struct.String.html#method.from_utf8_lossy pub fn command_line_lossy(&self) -> String { fn convert_word<S: AsRef<OsStr>>(word: S) -> String { fn char_requires_quoting(c: char) -> bool { if c.is_ascii_alphanumeric() { return false; } let allowed_chars = "/-,:.="; !allowed_chars.contains(c) } let s = String::from_utf8_lossy(word.as_ref().as_bytes()).to_string(); if s.chars().any(char_requires_quoting) { format!("'{}'", s) } else { s } } let mut out = convert_word(&self.program); for arg in &self.args { out.push(' '); out.push_str(&convert_word(arg)); } out } } impl Default for Command { fn default() -> Self { Command { program: PathBuf::new(), args: Vec::new(), dir: None, log_to: LogTo::Stdout, log_command: true, log_output_on_error: false, check: true, capture: false, combine_output: false, clear_env: false, env: HashMap::new(), } } } impl From<&Command> for process::Command { fn from(cmd: &Command) -> Self { let mut out = process::Command::new(&cmd.program); out.args(&cmd.args); if let Some(dir) = &cmd.dir { out.current_dir(dir); } if cmd.clear_env { out.env_clear(); } out.envs(&cmd.env); out } }