Implement address compilation

README.md

@@ -8,8 +8,9 @@
 # sed
 
 Rust reimplementation of the [sed utility](https://pubs.opengroup.org/onlinepubs/9799919799/utilities/sed.html)
-with some [GNU sed](https://www.gnu.org/software/sed/manual/sed.html)
-and [FreeBSD sed](https://man.freebsd.org/cgi/man.cgi?sed(1)) extensions.
+with some [GNU sed](https://www.gnu.org/software/sed/manual/sed.html),
+[FreeBSD sed](https://man.freebsd.org/cgi/man.cgi?sed(1)),
+and other extensions.
 
 ## Installation
 
@@ -23,6 +24,17 @@ cd sed
 cargo build --release
 cargo run --release
 ```
+## Extensions
+### GNU
+* Command-line arguments can be specified in long (`--`) form.
+* Spaces can precede a regular expression modifier.
+
+### BSD and GNU
+* The second address in a range can be specified as a relative address with +N.
+
+### Other
+* Unicode characters can be specified in regular expression pattern, replacement
+  and transliteration sequences using `\uXXXX` or `\UXXXXXXXX` sequences.
 
 ## License
 

src/uu/sed/src/command.rs

@@ -18,7 +18,7 @@ use std::path::PathBuf; // For file descriptors and equivalent
 
 // Compilation and processing options provided mostly through the
 // command-line interface
-#[derive(Debug)]
+#[derive(Debug, Default)]
 pub struct CliOptions {
     // Command-line flags with corresponding names
     pub all_output_files: bool,
@@ -107,6 +107,21 @@ pub struct Command {
     pub next: Option<Box<Command>>, // Pointer to next command
 }
 
+impl Default for Command {
+    fn default() -> Self {
+        Command {
+            code: '_',
+            addr1: None,
+            addr2: None,
+            non_select: false,
+            start_line: Some(0),
+            text: None,
+            data: CommandData::None,
+            next: None,
+        }
+    }
+}
+
 #[derive(Debug)]
 pub enum CommandData {
     None,