Strip overstriking to better support man pages

src/preprocessor.rs

@@ -1,3 +1,4 @@
+use std::borrow::Cow;
 use std::fmt::Write;
 
 use crate::{
@@ -149,6 +150,31 @@ pub fn strip_ansi(line: &str) -> String {
     buffer
 }
 
+/// Strips overstrike sequences (backspace formatting) from input.
+///
+/// Overstrike formatting is used by man pages and some help output:
+/// - Bold: `X\x08X` (character, backspace, same character)
+/// - Underline: `_\x08X` (underscore, backspace, character)
+///
+/// This function removes these sequences, keeping only the visible character.
+pub fn strip_overstrike(line: &str) -> Cow<'_, str> {
+    if !line.contains('\x08') {
+        return Cow::Borrowed(line);
+    }
+
+    let mut output = String::with_capacity(line.len());
+
+    for c in line.chars() {
+        if c == '\x08' {
+            output.pop();
+        } else {
+            output.push(c);
+        }
+    }
+
+    Cow::Owned(output)
+}
+
 #[derive(Debug, PartialEq, Clone, Copy, Default)]
 pub enum StripAnsiMode {
     #[default]
@@ -211,3 +237,30 @@ fn test_strip_ansi() {
         "multiple sequences"
     );
 }
+
+#[test]
+fn test_strip_overstrike() {
+    // No overstrike - should return borrowed reference
+    assert_eq!(strip_overstrike("no overstrike"), "no overstrike");
+
+    // Empty string
+    assert_eq!(strip_overstrike(""), "");
+
+    // Bold: X\x08X (same char repeated)
+    assert_eq!(strip_overstrike("H\x08Hello"), "Hello");
+
+    // Underline: _\x08X (underscore before char)
+    assert_eq!(strip_overstrike("_\x08Hello"), "Hello");
+
+    // Multiple overstrike sequences
+    assert_eq!(strip_overstrike("B\x08Bo\x08ol\x08ld\x08d"), "Bold");
+
+    // Backspace at start of line (nothing to pop)
+    assert_eq!(strip_overstrike("\x08Hello"), "Hello");
+
+    // Multiple consecutive backspaces
+    assert_eq!(strip_overstrike("ABC\x08\x08\x08XYZ"), "XYZ");
+
+    // Unicode with overstrike
+    assert_eq!(strip_overstrike("ä\x08äöü"), "äöü");
+}

src/printer.rs

@@ -1,3 +1,4 @@
+use std::borrow::Cow;
 use std::vec::Vec;
 
 use nu_ansi_term::Color::{Fixed, Green, Red, Yellow};
@@ -29,8 +30,7 @@ use crate::error::*;
 use crate::input::OpenedInput;
 use crate::line_range::{MaxBufferedLineNumber, RangeCheckResult};
 use crate::output::OutputHandle;
-use crate::preprocessor::strip_ansi;
+use crate::preprocessor::{expand_tabs, replace_nonprintable, strip_ansi, strip_overstrike};
-use crate::preprocessor::{expand_tabs, replace_nonprintable};
 use crate::style::StyleComponent;
 use crate::terminal::{as_terminal_escaped, to_ansi_color};
 use crate::vscreen::{AnsiStyle, EscapeSequence, EscapeSequenceIterator};
@@ -152,7 +152,7 @@ impl Printer for SimplePrinter<'_> {
                     self.config.nonprintable_notation,
                 );
                 write!(handle, "{line}")?;
-            } else {
+            } else if self.config.binary == BinaryBehavior::AsText {
                 match handle {
                     OutputHandle::IoWrite(handle) => handle.write_all(line_buffer)?,
                     OutputHandle::FmtWrite(handle) => {
@@ -166,6 +166,23 @@ impl Printer for SimplePrinter<'_> {
                         )?;
                     }
                 }
+            } else {
+                match handle {
+                    OutputHandle::IoWrite(handle) => {
+                        // Only strip overstrike for valid UTF-8, otherwise write raw bytes
+                        if let Ok(line) = std::str::from_utf8(line_buffer) {
+                            let line = strip_overstrike(line);
+                            handle.write_all(line.as_bytes())?;
+                        } else {
+                            handle.write_all(line_buffer)?;
+                        }
+                    }
+                    OutputHandle::FmtWrite(handle) => {
+                        let line = String::from_utf8_lossy(line_buffer);
+                        let line = strip_overstrike(&line);
+                        write!(handle, "{line}")?;
+                    }
+                }
             };
         }
         Ok(())
@@ -622,6 +639,11 @@ impl Printer for InteractivePrinter<'_> {
                 }
             };
 
+            // Strip overstrike sequences (used by man pages for bold/underline).
+            if line.contains('\x08') {
+                line = Cow::Owned(strip_overstrike(&line).into_owned());
+            }
+
             // If ANSI escape sequences are supposed to be stripped, do it before syntax highlighting.
             if self.strip_ansi {
                 line = strip_ansi(&line).into()