Implement silent comment command

src/uu/sed/src/compiler.rs

@@ -78,7 +78,6 @@ pub fn compile(
     }
     patch_block_endings(result.clone());
 
-    // TODO: setup append & match structures
     Ok(result)
 }
 
@@ -229,8 +228,25 @@ fn compile_sequence(
 
     loop {
         line.eat_spaces();
+
+        // According to POSIX: "If the first two characters in the script are
+        // "#n", the default output shall be suppressed".
+        if !line.eol()
+            && line.current() == '#'
+            && lines.get_line_number() == 1
+            && line.get_pos() == 0
+        {
+            line.advance();
+            if !line.eol() && line.current() == 'n' {
+                context.quiet = true;
+            }
+            // Ignore rest of line
+            while !line.eol() {
+                line.advance();
+            }
+        }
+
         if line.eol() || line.current() == '#' {
-            // TODO: set context.quiet for StringVal starting with #n
             match lines.next_line()? {
                 None => {
                     return Ok(head);

tests/by-util/test_sed.rs

@@ -154,6 +154,12 @@ const LINES1: &str = "input/lines1";
 const LINES2: &str = "input/lines2";
 const NO_NEW_LINE: &str = "input/no-new-line.txt";
 
+////////////////////////////////////////////////////////////
+// Comments
+check_output!(comment, ["-n", "-e", "4p;# comment", LINES1]);
+check_output!(comment_silent, ["-e", "#n", "-e", "4p", LINES1]);
+check_output!(comment_no_silent, ["-e", "4p;#n comment", LINES1]);
+
 ////////////////////////////////////////////////////////////
 // Address ranges: One and two, numeric and pattern
 check_output!(addr_one_line, ["-n", "-e", "4p", LINES1]);

tests/fixtures/sed/output/comment

@@ -0,0 +1 @@
+l1_4

tests/fixtures/sed/output/comment_no_silent

@@ -0,0 +1,15 @@
+l1_1
+l1_2
+l1_3
+l1_4
+l1_4
+l1_5
+l1_6
+l1_7
+l1_8
+l1_9
+l1_10
+l1_11
+l1_12
+l1_13
+l1_14

tests/fixtures/sed/output/comment_silent

@@ -0,0 +1 @@
+l1_4