diff --git a/WDL/runtime/task.py b/WDL/runtime/task.py
index cf7b1b37..cf7ac85b 100644
--- a/WDL/runtime/task.py
+++ b/WDL/runtime/task.py
@@ -491,17 +491,30 @@ def _parse_boolean(s: str) -> WDL.Value.Boolean:
 
         self._override_static("read_boolean", _read_something(_parse_boolean))
 
-        def _read_lines(container_file: WDL.Value.File, lib: _StdLib = self) -> WDL.Value.Array:
-            host_file = lib.container.host_file(container_file.value, lib.inputs_only)
+        def parse_lines(s: str) -> WDL.Value.Array:
             ans = []
-            with open(host_file, "r") as infile:
-                for line in infile:
-                    if line.endswith("\n"):
-                        line = line[:-1]
-                    ans.append(WDL.Value.String(line))
+            if s:
+                ans = [
+                    WDL.Value.String(line)
+                    for line in (s[:-1] if s.endswith("\n") else s).split("\n")
+                ]
             return WDL.Value.Array(WDL.Type.Array(WDL.Type.String()), ans)
 
-        self._override_static("read_lines", _read_lines)
+        self._override_static("read_lines", _read_something(parse_lines))
+
+        def parse_tsv(s: str) -> WDL.Value.Array:
+            # TODO: should a blank line parse as [] or ['']?
+            ans = [
+                WDL.Value.Array(
+                    WDL.Type.Array(WDL.Type.String()),
+                    [WDL.Value.String(field) for field in line.value.split("\t")],
+                )
+                for line in parse_lines(s).value
+            ]
+            # pyre-ignore
+            return WDL.Value.Array(WDL.Type.Array(WDL.Type.Array(WDL.Type.String())), ans)
+
+        self._override_static("read_tsv", _read_something(parse_tsv))
 
         def _write_something(
             serialize: Callable[[WDL.Value.Base, BinaryIO], None], lib: _StdLib = self
@@ -538,6 +551,22 @@ def _serialize_lines(array: WDL.Value.Array, outfile: BinaryIO) -> None:
             _write_something(lambda v, outfile: outfile.write(json.dumps(v.json).encode("utf-8"))),
         )
 
+        self._override_static(
+            "write_tsv",
+            _write_something(
+                lambda v, outfile: _serialize_lines(
+                    WDL.Value.Array(
+                        WDL.Type.Array(WDL.Type.String()),
+                        [
+                            WDL.Value.String("\t".join([part.value for part in parts.value]))
+                            for parts in v.value
+                        ],
+                    ),
+                    outfile,
+                )
+            ),
+        )
+
 
 class InputStdLib(_StdLib):
     # StdLib for evaluation of task inputs and command
diff --git a/tests/test_5stdlib.py b/tests/test_5stdlib.py
index 6b61e996..75ccc19b 100644
--- a/tests/test_5stdlib.py
+++ b/tests/test_5stdlib.py
@@ -441,6 +441,7 @@ def test_write(self):
         version 1.0
         task hello {
             File foo = write_lines(["foo","bar","baz"])
+            File tsv = write_tsv([["one", "two", "three"], ["un", "deux", "trois"]])
             File json = write_json({"key1": "value1", "key2": "value2"})
 
             command <<<
@@ -448,12 +449,18 @@ def test_write(self):
                 if [ "$foo_sha" != "b1b113c6ed8ab3a14779f7c54179eac2b87d39fcebbf65a50556b8d68caaa2fb" ]; then
                     exit 1
                 fi
+                tsv_sha=$(sha256sum < ~{tsv} | cut -f1 -d ' ')
+                if [ "$tsv_sha" != "a7124e688203195cd674cf147bbf965eda49e8df581d01c05944330fab096084" ]; then
+                    exit 1
+                fi
             >>>
 
             output {
                 File o_json = json
+                Array[Array[String]] o_tsv = read_tsv(tsv)
             }
         }
         """)
         with open(outputs["o_json"]) as infile:
             self.assertEqual(json.load(infile), {"key1": "value1", "key2": "value2"})
+        self.assertEqual(outputs["o_tsv"], [["one", "two", "three"], ["un", "deux", "trois"]])