diff --git a/Makefile b/Makefile
index 63ad5c739..ca4309339 100644
--- a/Makefile
+++ b/Makefile
@@ -23,6 +23,7 @@ PROGS       := \
   rmdir \
   sleep \
   seq \
+  tac \
   tee \
   true \
   truncate \
diff --git a/README.md b/README.md
index 3e2fe76a4..593a493ee 100644
--- a/README.md
+++ b/README.md
@@ -95,7 +95,6 @@ To do
 - fold
 - getlimits
 - group-list
-- groups
 - hostid
 - install
 - join
@@ -144,7 +143,6 @@ To do
 - sum
 - sync
 - tac-pipe
-- tac
 - tail
 - test
 - timeout
diff --git a/common/util.rs b/common/util.rs
index 2968b6822..e26c715e5 100644
--- a/common/util.rs
+++ b/common/util.rs
@@ -26,6 +26,16 @@ macro_rules! crash(
     })
 )
 
+#[macro_export]
+macro_rules! crash_if_err(
+    ($exitcode:expr, $exp:expr) => (
+        match $exp {
+            Ok(m) => m,
+            Err(f) => crash!($exitcode, "{}", f.to_str())
+        }
+    )
+)
+
 #[macro_export]
 macro_rules! safe_write(
     ($fd:expr, $($args:expr),+) => (
diff --git a/tac/tac.rs b/tac/tac.rs
new file mode 100644
index 000000000..fe6340478
--- /dev/null
+++ b/tac/tac.rs
@@ -0,0 +1,76 @@
+#[crate_id(name = "tac", vers = "1.0.0", author = "Arcterus")];
+
+/*
+ * This file is part of the uutils coreutils package.
+ *
+ * (c) Arcterus <arcterus@mail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+#[feature(macro_rules)];
+
+extern crate getopts;
+
+use std::io;
+use std::os;
+
+#[path = "../common/util.rs"]
+mod util;
+
+static NAME: &'static str = "tac";
+static VERSION: &'static str = "1.0.0";
+
+fn main() {
+    let args = os::args();
+    let program = args[0].clone();
+
+    let opts = ~[
+        getopts::optflag("b", "before", "attach the separator before instead of after"),
+        getopts::optflag("r", "regex", "interpret the sequence as a regular expression (NOT IMPLEMENTED)"),
+        getopts::optopt("s", "separator", "use STRING as the separator instead of newline", "STRING"),
+        getopts::optflag("h", "help", "display this help and exit"),
+        getopts::optflag("V", "version", "output version information and exit")
+    ];
+    let matches = match getopts::getopts(args.tail(), opts) {
+        Ok(m) => m,
+        Err(f) => crash!(1, "{}", f.to_err_msg())
+    };
+    if matches.opt_present("help") {
+        println!("tac {}", VERSION);
+        println!("");
+        println!("Usage:");
+        println!("  {0:s} [OPTION]... [FILE]...", program);
+        println!("");
+        print!("{}", getopts::usage("Write each file to standard output, last line first.", opts));
+    } else if matches.opt_present("version") {
+        println!("tac {}", VERSION);
+    } else {
+        let before = matches.opt_present("b");
+        let regex = matches.opt_present("r");
+        let separator = match matches.opt_str("s") {
+            Some(m) => m,
+            None => ~"\n"
+        };
+        tac(matches.free, before, regex, separator);
+    }
+}
+
+fn tac(filenames: ~[~str], before: bool, _: bool, separator: ~str) {
+    for filename in filenames.move_iter() {
+        let mut file = io::BufferedReader::new(
+                           crash_if_err!(1, io::File::open(&Path::new(filename))));
+        let data = crash_if_err!(1, file.read_to_str());
+        let mut split_vec: ~[&str] = data.split_str(separator).collect();
+        split_vec.pop();  // removes blank line that is inserted otherwise
+        let rev: ~str = split_vec.rev_iter().fold(~"", |a, &b|
+            a + if before {
+                separator + b
+            } else {
+                b + separator
+            }
+        );
+        print!("{}", rev);
+    }
+}