feat(builtins): implement yes and realpath builtins

yes: repeatedly output a string (with 10K line safety limit)
realpath: resolve absolute pathname with . and .. normalization

https://claude.ai/code/session_012rzB3FRw7yoQWCG1mxyW7J

Author: claude

crates/bashkit/src/builtins/mod.rs

@@ -63,6 +63,7 @@ mod timeout;
 mod vars;
 mod wait;
 mod wc;
+mod yes;
 
 #[cfg(feature = "git")]
 mod git;
@@ -94,7 +95,7 @@ pub use ls::{Find, Ls, Rmdir};
 pub use navigation::{Cd, Pwd};
 pub use nl::Nl;
 pub use paste::Paste;
-pub use path::{Basename, Dirname};
+pub use path::{Basename, Dirname, Realpath};
 pub use pipeline::{Tee, Watch, Xargs};
 pub use printf::Printf;
 pub use read::Read;
@@ -111,6 +112,7 @@ pub use timeout::Timeout;
 pub use vars::{Eval, Local, Readonly, Set, Shift, Shopt, Times, Unset};
 pub use wait::Wait;
 pub use wc::Wc;
+pub use yes::Yes;
 
 #[cfg(feature = "git")]
 pub use git::Git;

crates/bashkit/src/builtins/path.rs

@@ -119,6 +119,38 @@ impl Builtin for Dirname {
     }
 }
 
+/// The realpath builtin - resolve absolute pathname.
+///
+/// Usage: realpath [PATH...]
+///
+/// Resolves `.` and `..` components and prints absolute canonical paths.
+/// In bashkit's virtual filesystem, symlink resolution is not performed.
+pub struct Realpath;
+
+#[async_trait]
+impl Builtin for Realpath {
+    async fn execute(&self, ctx: Context<'_>) -> Result<ExecResult> {
+        if ctx.args.is_empty() {
+            return Ok(ExecResult::err(
+                "realpath: missing operand\n".to_string(),
+                1,
+            ));
+        }
+
+        let mut output = String::new();
+        for arg in ctx.args {
+            if arg.starts_with('-') {
+                continue; // skip flags like -e, -m, -s
+            }
+            let resolved = super::resolve_path(ctx.cwd, arg);
+            output.push_str(&resolved.to_string_lossy());
+            output.push('\n');
+        }
+
+        Ok(ExecResult::ok(output))
+    }
+}
+
 #[cfg(test)]
 #[allow(clippy::unwrap_used)]
 mod tests {

crates/bashkit/src/builtins/yes.rs

@@ -0,0 +1,37 @@
+//! yes builtin - repeatedly output a line
+
+use async_trait::async_trait;
+
+use super::{Builtin, Context};
+use crate::error::Result;
+use crate::interpreter::ExecResult;
+
+/// The yes builtin - output a string repeatedly.
+///
+/// Usage: yes [STRING]
+///
+/// Repeatedly outputs STRING (default: "y") followed by newline.
+/// In bashkit, output is limited to avoid infinite loops.
+pub struct Yes;
+
+/// Maximum number of lines to output (safety limit)
+const MAX_LINES: usize = 10_000;
+
+#[async_trait]
+impl Builtin for Yes {
+    async fn execute(&self, ctx: Context<'_>) -> Result<ExecResult> {
+        let text = if ctx.args.is_empty() {
+            "y".to_string()
+        } else {
+            ctx.args.join(" ")
+        };
+
+        let mut output = String::new();
+        for _ in 0..MAX_LINES {
+            output.push_str(&text);
+            output.push('\n');
+        }
+
+        Ok(ExecResult::ok(output))
+    }
+}

crates/bashkit/src/interpreter/mod.rs

@@ -237,6 +237,7 @@ impl Interpreter {
         builtins.insert("tail".to_string(), Box::new(builtins::Tail));
         builtins.insert("basename".to_string(), Box::new(builtins::Basename));
         builtins.insert("dirname".to_string(), Box::new(builtins::Dirname));
+        builtins.insert("realpath".to_string(), Box::new(builtins::Realpath));
         builtins.insert("mkdir".to_string(), Box::new(builtins::Mkdir));
         builtins.insert("mktemp".to_string(), Box::new(builtins::Mktemp));
         builtins.insert("rm".to_string(), Box::new(builtins::Rm));
@@ -260,6 +261,7 @@ impl Interpreter {
         builtins.insert("seq".to_string(), Box::new(builtins::Seq));
         builtins.insert("tac".to_string(), Box::new(builtins::Tac));
         builtins.insert("rev".to_string(), Box::new(builtins::Rev));
+        builtins.insert("yes".to_string(), Box::new(builtins::Yes));
         builtins.insert("sort".to_string(), Box::new(builtins::Sort));
         builtins.insert("uniq".to_string(), Box::new(builtins::Uniq));
         builtins.insert("cut".to_string(), Box::new(builtins::Cut));

crates/bashkit/tests/spec_cases/bash/path.test.sh

@@ -97,3 +97,35 @@ dirname file
 ### expect
 .
 ### end
+
+### realpath_absolute
+# realpath resolves .. components
+### bash_diff
+realpath /tmp/../tmp/test
+### expect
+/tmp/test
+### end
+
+### realpath_dot
+# realpath resolves . components
+### bash_diff
+realpath /home/user/./file.txt
+### expect
+/home/user/file.txt
+### end
+
+### realpath_dotdot
+# realpath resolves parent directory references
+### bash_diff
+realpath /home/user/docs/../file.txt
+### expect
+/home/user/file.txt
+### end
+
+### realpath_no_args
+# realpath with no args should error
+realpath 2>/dev/null
+echo $?
+### expect
+1
+### end

crates/bashkit/tests/spec_cases/bash/textrev.test.sh

@@ -90,3 +90,28 @@ echo "a b c" | rev
 ### expect
 c b a
 ### end
+
+### yes_default
+# yes outputs "y" by default (piped through head)
+yes | head -3
+### expect
+y
+y
+y
+### end
+
+### yes_custom_string
+# yes with custom string
+yes hello | head -2
+### expect
+hello
+hello
+### end
+
+### yes_multiple_args
+# yes joins multiple args with space
+yes a b c | head -2
+### expect
+a b c
+a b c
+### end

specs/009-implementation-status.md

@@ -103,17 +103,17 @@ Bashkit implements IEEE 1003.1-2024 Shell Command Language. See
 
 ## Spec Test Coverage
 
-**Total spec test cases:** 1369 (1364 pass, 5 skip)
+**Total spec test cases:** 1376 (1371 pass, 5 skip)
 
 | Category | Cases | In CI | Pass | Skip | Notes |
 |----------|-------|-------|------|------|-------|
-| Bash (core) | 951 | Yes | 946 | 5 | `bash_spec_tests` in CI |
+| Bash (core) | 958 | Yes | 953 | 5 | `bash_spec_tests` in CI |
 | AWK | 96 | Yes | 96 | 0 | loops, arrays, -v, ternary, field assign, getline, %.6g |
 | Grep | 76 | Yes | 76 | 0 | -z, -r, -a, -b, -H, -h, -f, -P, --include, --exclude, binary detect |
 | Sed | 75 | Yes | 75 | 0 | hold space, change, regex ranges, -E |
 | JQ | 114 | Yes | 114 | 0 | reduce, walk, regex funcs, --arg/--argjson, combined flags, input/inputs, env |
 | Python | 57 | Yes | 57 | 0 | embedded Python (Monty) |
-| **Total** | **1369** | **Yes** | **1364** | **5** | |
+| **Total** | **1376** | **Yes** | **1371** | **5** | |
 
 ### Bash Spec Tests Breakdown
 
@@ -147,7 +147,7 @@ Bashkit implements IEEE 1003.1-2024 Shell Command Language. See
 | nl.test.sh | 14 | line numbering |
 | nounset.test.sh | 7 | `set -u` unbound variable checks, `${var:-default}` nounset-aware |
 | paste.test.sh | 4 | line merging with `-s` serial and `-d` delimiter |
-| path.test.sh | 14 | |
+| path.test.sh | 18 | basename, dirname, `realpath` canonical path resolution |
 | pipes-redirects.test.sh | 19 | includes stderr redirects |
 | printf.test.sh | 32 | format specifiers, array expansion, `-v` variable assignment, `%q` shell quoting |
 | procsub.test.sh | 6 | |
@@ -165,7 +165,7 @@ Bashkit implements IEEE 1003.1-2024 Shell Command Language. See
 | eval-bugs.test.sh | 4 | regression tests for eval/script bugs |
 | script-exec.test.sh | 10 | script execution by path, $PATH search, exit codes |
 | seq.test.sh | 12 | `seq` numeric sequences, `-w`, `-s`, decrement, negative |
-| textrev.test.sh | 11 | `tac` reverse line order, `rev` reverse characters |
+| textrev.test.sh | 14 | `tac` reverse line order, `rev` reverse characters, `yes` repeated output |
 | heredoc.test.sh | 10 | heredoc variable expansion, quoted delimiters, file redirects, `<<-` tab strip |
 | string-ops.test.sh | 14 | string replacement (prefix/suffix anchored), `${var:?}`, case conversion |
 | read-builtin.test.sh | 10 | `read` builtin, IFS splitting, `-r`, `-a` (array), `-n` (nchars), here-string |