stty: columns env support and integration testing

src/uu/stty/src/stty.rs

@@ -539,8 +539,71 @@ fn print_special_setting(setting: &PrintSetting, fd: i32) -> nix::Result<()> {
     Ok(())
 }
 
-fn print_terminal_size(termios: &Termios, opts: &Options) -> nix::Result<()> {
+/// Handles line wrapping for stty output to fit within terminal width
+struct WrappedPrinter {
+    width: usize,
+    current: usize,
+    first_in_line: bool,
+}
+
+impl WrappedPrinter {
+    /// Creates a new printer with the specified terminal width.
+    /// If term_size is None (typically when output is piped), falls back to
+    /// the COLUMNS environment variable or a default width of 80 columns.
+    fn new(term_size: Option<&TermSize>) -> Self {
+        let columns = match term_size {
+            Some(term_size) => term_size.columns,
+            None => {
+                const DEFAULT_TERM_WIDTH: u16 = 80;
+
+                std::env::var_os("COLUMNS")
+                    .and_then(|s| s.to_str()?.parse().ok())
+                    .filter(|&c| c > 0)
+                    .unwrap_or(DEFAULT_TERM_WIDTH)
+            }
+        };
+
+        Self {
+            width: columns.max(1) as usize,
+            current: 0,
+            first_in_line: true,
+        }
+    }
+
+    fn print(&mut self, token: &str) {
+        let token_len = self.prefix().chars().count() + token.chars().count();
+        if self.current > 0 && self.current + token_len > self.width {
+            println!();
+            self.current = 0;
+            self.first_in_line = true;
+        }
+
+        print!("{}{}", self.prefix(), token);
+        self.current += token_len;
+        self.first_in_line = false;
+    }
+
+    fn prefix(&self) -> &str {
+        if self.first_in_line { "" } else { " " }
+    }
+
+    fn flush(&mut self) {
+        if self.current > 0 {
+            println!();
+            self.current = 0;
+            self.first_in_line = false;
+        }
+    }
+}
+
+fn print_terminal_size(
+    termios: &Termios,
+    opts: &Options,
+    window_size: Option<&TermSize>,
+    term_size: Option<&TermSize>,
+) -> nix::Result<()> {
     let speed = cfgetospeed(termios);
+    let mut printer = WrappedPrinter::new(window_size);
 
     // BSDs use a u32 for the baud rate, so we can simply print it.
     #[cfg(any(
@@ -551,7 +614,7 @@ fn print_terminal_size(termios: &Termios, opts: &Options) -> nix::Result<()> {
         target_os = "netbsd",
         target_os = "openbsd"
     ))]
-    print!("{} ", translate!("stty-output-speed", "speed" => speed));
+    printer.print(&translate!("stty-output-speed", "speed" => speed));
 
     // Other platforms need to use the baud rate enum, so printing the right value
     // becomes slightly more complicated.
@@ -565,17 +628,15 @@ fn print_terminal_size(termios: &Termios, opts: &Options) -> nix::Result<()> {
     )))]
     for (text, baud_rate) in BAUD_RATES {
         if *baud_rate == speed {
-            print!("{} ", translate!("stty-output-speed", "speed" => (*text)));
+            printer.print(&translate!("stty-output-speed", "speed" => (*text)));
             break;
         }
     }
 
     if opts.all {
-        let mut size = TermSize::default();
-        unsafe { tiocgwinsz(opts.file.as_raw_fd(), &raw mut size)? };
-        print!(
-            "{} ",
-            translate!("stty-output-rows-columns", "rows" => size.rows, "columns" => size.columns)
+        let term_size = term_size.as_ref().expect("terminal size should be set");
+        printer.print(
+            &translate!("stty-output-rows-columns", "rows" => term_size.rows, "columns" => term_size.columns),
         );
     }
 
@@ -585,10 +646,9 @@ fn print_terminal_size(termios: &Termios, opts: &Options) -> nix::Result<()> {
         // so we get the underlying libc::termios struct to get that information.
         let libc_termios: nix::libc::termios = termios.clone().into();
         let line = libc_termios.c_line;
-        print!("{}", translate!("stty-output-line", "line" => line));
+        printer.print(&translate!("stty-output-line", "line" => line));
     }
-
-    println!();
+    printer.flush();
     Ok(())
 }
 
@@ -756,39 +816,41 @@ fn control_char_to_string(cc: nix::libc::cc_t) -> nix::Result<String> {
     Ok(format!("{meta_prefix}{ctrl_prefix}{character}"))
 }
 
-fn print_control_chars(termios: &Termios, opts: &Options) -> nix::Result<()> {
+fn print_control_chars(
+    termios: &Termios,
+    opts: &Options,
+    term_size: Option<&TermSize>,
+) -> nix::Result<()> {
     if !opts.all {
         // Print only control chars that differ from sane defaults
-        let mut printed = false;
+        let mut printer = WrappedPrinter::new(term_size);
         for (text, cc_index) in CONTROL_CHARS {
             let current_val = termios.control_chars[*cc_index as usize];
             let sane_val = get_sane_control_char(*cc_index);
 
             if current_val != sane_val {
-                print!("{text} = {}; ", control_char_to_string(current_val)?);
-                printed = true;
+                printer.print(&format!(
+                    "{text} = {};",
+                    control_char_to_string(current_val)?
+                ));
             }
         }
-
-        if printed {
-            println!();
-        }
+        printer.flush();
         return Ok(());
     }
 
+    let mut printer = WrappedPrinter::new(term_size);
     for (text, cc_index) in CONTROL_CHARS {
-        print!(
-            "{text} = {}; ",
+        printer.print(&format!(
+            "{text} = {};",
             control_char_to_string(termios.control_chars[*cc_index as usize])?
-        );
+        ));
     }
-    println!(
-        "{}",
-        translate!("stty-output-min-time",
+    printer.print(&translate!("stty-output-min-time",
         "min" => termios.control_chars[S::VMIN as usize],
         "time" => termios.control_chars[S::VTIME as usize]
-        )
-    );
+    ));
+    printer.flush();
     Ok(())
 }
 
@@ -806,22 +868,48 @@ fn print_in_save_format(termios: &Termios) {
     println!();
 }
 
+/// Gets terminal size using the tiocgwinsz ioctl system call.
+/// This queries the kernel for the current terminal window dimensions.
+fn get_terminal_size(fd: RawFd) -> nix::Result<TermSize> {
+    let mut term_size = TermSize::default();
+    unsafe { tiocgwinsz(fd, &raw mut term_size) }.map(|_| term_size)
+}
+
 fn print_settings(termios: &Termios, opts: &Options) -> nix::Result<()> {
     if opts.save {
         print_in_save_format(termios);
     } else {
-        print_terminal_size(termios, opts)?;
-        print_control_chars(termios, opts)?;
-        print_flags(termios, opts, CONTROL_FLAGS);
-        print_flags(termios, opts, INPUT_FLAGS);
-        print_flags(termios, opts, OUTPUT_FLAGS);
-        print_flags(termios, opts, LOCAL_FLAGS);
+        let device_fd = opts.file.as_raw_fd();
+        let term_size = if opts.all {
+            Some(get_terminal_size(device_fd)?)
+        } else {
+            get_terminal_size(device_fd).ok()
+        };
+
+        let stdout_fd = stdout().as_raw_fd();
+        let window_size = if device_fd == stdout_fd {
+            &term_size
+        } else {
+            &get_terminal_size(stdout_fd).ok()
+        };
+
+        print_terminal_size(termios, opts, window_size.as_ref(), term_size.as_ref())?;
+        print_control_chars(termios, opts, window_size.as_ref())?;
+        print_flags(termios, opts, CONTROL_FLAGS, window_size.as_ref());
+        print_flags(termios, opts, INPUT_FLAGS, window_size.as_ref());
+        print_flags(termios, opts, OUTPUT_FLAGS, window_size.as_ref());
+        print_flags(termios, opts, LOCAL_FLAGS, window_size.as_ref());
     }
     Ok(())
 }
 
-fn print_flags<T: TermiosFlag>(termios: &Termios, opts: &Options, flags: &[Flag<T>]) {
-    let mut printed = false;
+fn print_flags<T: TermiosFlag>(
+    termios: &Termios,
+    opts: &Options,
+    flags: &[Flag<T>],
+    term_size: Option<&TermSize>,
+) {
+    let mut printer = WrappedPrinter::new(term_size);
     for &Flag {
         name,
         flag,
@@ -836,20 +924,17 @@ fn print_flags<T: TermiosFlag>(termios: &Termios, opts: &Options, flags: &[Flag<
         let val = flag.is_in(termios, group);
         if group.is_some() {
             if val && (!sane || opts.all) {
-                print!("{name} ");
-                printed = true;
+                printer.print(name);
             }
         } else if opts.all || val != sane {
             if !val {
-                print!("-");
+                printer.print(&format!("-{name}"));
+                continue;
             }
-            print!("{name} ");
-            printed = true;
+            printer.print(name);
         }
     }
-    if printed {
-        println!();
-    }
+    printer.flush();
 }
 
 /// Apply a single setting

tests/by-util/test_stty.rs

@@ -526,3 +526,60 @@ fn test_saved_state_with_control_chars() {
         .stderr_is(exp_result.stderr_str())
         .code_is(exp_result.code());
 }
+
+#[test]
+#[cfg(unix)]
+fn test_columns_env_wrapping() {
+    use std::process::Stdio;
+    let (path, _controller, _replica) = pty_path();
+
+    // Must pipe output so stty uses COLUMNS env instead of actual terminal size
+    for (columns, max_len) in [(20, 20), (40, 40), (50, 50)] {
+        let result = new_ucmd!()
+            .args(&["--all", "--file", &path])
+            .env("COLUMNS", columns.to_string())
+            .set_stdout(Stdio::piped())
+            .succeeds();
+
+        for line in result.stdout_str().lines() {
+            assert!(
+                line.len() <= max_len,
+                "Line exceeds COLUMNS={columns}: '{line}'"
+            );
+        }
+    }
+
+    // Wide columns should allow longer lines
+    let result = new_ucmd!()
+        .args(&["--all", "--file", &path])
+        .env("COLUMNS", "200")
+        .set_stdout(Stdio::piped())
+        .succeeds();
+    let has_long_line = result.stdout_str().lines().any(|line| line.len() > 80);
+    assert!(
+        has_long_line,
+        "Expected at least one line longer than 80 chars with COLUMNS=200"
+    );
+
+    // Invalid values should fall back to default
+    for invalid in ["invalid", "0", "-10"] {
+        new_ucmd!()
+            .args(&["--all", "--file", &path])
+            .env("COLUMNS", invalid)
+            .set_stdout(Stdio::piped())
+            .succeeds();
+    }
+
+    // Without --all flag
+    let result = new_ucmd!()
+        .args(&["--file", &path])
+        .env("COLUMNS", "30")
+        .set_stdout(Stdio::piped())
+        .succeeds();
+    for line in result.stdout_str().lines() {
+        assert!(
+            line.len() <= 30,
+            "Line exceeds COLUMNS=30 without --all: '{line}'"
+        );
+    }
+}