Implement tee -p

This amounts to enabling pipe errors when -p is not specified, but only
on unixish platforms.

src/uu/tee/src/tee.rs

@@ -27,13 +27,15 @@ mod options {
     pub const APPEND: &str = "append";
     pub const IGNORE_INTERRUPTS: &str = "ignore-interrupts";
     pub const FILE: &str = "file";
+    pub const IGNORE_PIPE_ERRORS: &str = "ignore-pipe-errors";
 }
 
 #[allow(dead_code)]
 struct Options {
     append: bool,
     ignore_interrupts: bool,
     files: Vec<String>,
+    ignore_pipe_errors: bool,
 }
 
 #[uucore::main]
@@ -47,6 +49,7 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
             .values_of(options::FILE)
             .map(|v| v.map(ToString::to_string).collect())
             .unwrap_or_default(),
+        ignore_pipe_errors: matches.is_present(options::IGNORE_PIPE_ERRORS),
     };
 
     match tee(&options) {
@@ -79,6 +82,11 @@ pub fn uu_app<'a>() -> Command<'a> {
                 .multiple_occurrences(true)
                 .value_hint(clap::ValueHint::FilePath),
         )
+        .arg(
+            Arg::new(options::IGNORE_PIPE_ERRORS)
+                .short('p')
+                .help("diagnose errors writing to non-pipes (ignored on non-Unix platforms)"),
+        )
 }
 
 #[cfg(unix)]
@@ -96,10 +104,28 @@ fn ignore_interrupts() -> Result<()> {
     Ok(())
 }
 
+#[cfg(unix)]
+fn enable_pipe_errors() -> Result<()> {
+    let ret = unsafe { libc::signal(libc::SIGPIPE, libc::SIG_DFL) };
+    if ret == libc::SIG_ERR {
+        return Err(Error::new(ErrorKind::Other, ""));
+    }
+    Ok(())
+}
+
+#[cfg(not(unix))]
+fn enable_pipe_errors() -> Result<()> {
+    // Do nothing.
+    Ok(())
+}
+
 fn tee(options: &Options) -> Result<()> {
     if options.ignore_interrupts {
         ignore_interrupts()?;
     }
+    if !options.ignore_pipe_errors {
+        enable_pipe_errors()?;
+    }
     let mut writers: Vec<NamedWriter> = options
         .files
         .clone()