Index: lit/lit/TestRunner.py
===================================================================
--- lit/lit/TestRunner.py
+++ lit/lit/TestRunner.py
@@ -1,7 +1,11 @@
 from __future__ import absolute_import
+import difflib
+import itertools
 import os, signal, subprocess, sys
 import re
+import stat
 import platform
+import shutil
 import tempfile
 import threading
 
@@ -302,6 +306,105 @@
         return stdout.getvalue()
     return ""
 
+def check_option_in_arg(option, arg, flag):
+    arg_without_option = filter(lambda char: char != option, arg)
+    flag = flag or (len(arg_without_option) != len(arg))
+    return flag, arg_without_option
+
+def executeBuiltinMkdir(cmd):
+    """executeBuiltinMkdir - Create new directories."""
+    # Implement mkdir flags. We only support -p option.
+    args = cmd.args[1:]
+    dirs = None
+    parent = False
+    for idx, arg in enumerate(args):
+        if arg[0] != '-':
+            dirs = args[idx:]
+            break
+        parent, remaining_arg = check_option_in_arg('p', arg[1:], parent)
+        if len(remaining_arg) > 0:
+            raise InternalShellError(cmd, "Unsupported: 'mkdir' does not "
+                                          "support -%s option" % remaining_arg)
+
+    if dirs is None:
+        raise InternalShellError(cmd, "Error: 'mkdir' is missing an operand")
+
+    for dir in dirs:
+        if parent:
+            lit.util.mkdir_p(dir)
+        else:
+            try:
+                os.mkdir(dir)
+            except OSError as e:
+                raise InternalShellError(cmd, "Error: 'mkdir' command failed")
+
+def executeBuiltinDiff(cmd):
+    """executeBuiltinDiff - Compare files line by line."""
+    if len(cmd.args) != 3:
+        raise InternalShellError(cmd, "Error: 'diff' only "
+                                      "supports a fromfile and tofile")
+
+    fromfile = cmd.args[1]
+    tofile = cmd.args[2]
+    different = False
+    try:
+        with open(fromfile, 'r') as f1, open(tofile, 'r') as f2:
+            for diff in difflib.context_diff(f1.readlines(),
+                                             f2.readlines(),
+                                             fromfile,
+                                             tofile):
+                sys.stdout.write(diff)
+                different = True
+    except IOError as e:
+        raise InternalShellError(cmd, "Error: 'diff' command failed")
+
+    if different:
+        raise InternalShellError(cmd, "Error: The contexts "
+                                      "of fromfile and tofile are different")
+
+def executeBuiltinRm(cmd, cmd_shenv):
+    """executeBuiltinRm - Removes (deletes) files or directories."""
+    # Expand all glob expressions
+    args = cmd.args[1:]
+    args = expand_glob_expressions(args, cmd_shenv.cwd)
+
+    # Implement rm flags. We only support -f and in combination with -r.
+    dirs = None
+    force = False
+    recursive = False
+    for idx, arg in enumerate(args):
+        if arg [0] != '-':
+            dirs = args[idx:]
+            break
+        force, arg = check_option_in_arg('f', arg[1:], force)
+        recursive, arg = check_option_in_arg('r', arg, recursive)
+        if len(arg) > 0:
+            raise InternalShellError(cmd, "Unsupported: 'rm' does not "
+                                          "support -%s option" % arg)
+
+    def on_rm_error(func, path, exc_info):
+        # path contains the path of the file that couldn't be removed
+        # let's just assume that it's read-only and remove it.
+        os.chmod(path, stat.S_IMODE( os.stat(path).st_mode) | stat.S_IWRITE)
+        os.remove(path)
+
+    for dir in dirs:
+        if force and not os.path.exists(dir):
+            continue
+        try:
+            if os.path.isdir(dir):
+                if not recursive:
+                    raise InternalShellError(cmd, "Error: "
+                                                  "%s is a directory" % dir)
+                shutil.rmtree(dir, onerror = on_rm_error if force else None)
+            else:
+                if force and not os.access(dir, os.W_OK):
+                    os.chmod(dir,
+                             stat.S_IMODE(os.stat(dir).st_mode) | stat.S_IWRITE)
+                os.remove(dir)
+        except OSError as e:
+            raise InternalShellError(cmd, "Error: 'rm' command failed")
+
 def processRedirects(cmd, stdin_source, cmd_shenv, opened_files):
     """Return the standard fds for cmd after applying redirects
 
@@ -460,6 +563,27 @@
         updateEnv(shenv, cmd.commands[0])
         return 0
 
+    if cmd.commands[0].args[0] == 'mkdir':
+        if len(cmd.commands) != 1:
+            raise InternalShellError(cmd.commands[0], "Unsupported: 'mkdir' "
+                                     "cannot be part of a pipeline")
+        executeBuiltinMkdir(cmd.commands[0])
+        return 0
+
+    if cmd.commands[0].args[0] == 'diff':
+        if len(cmd.commands) != 1:
+            raise InternalShellError(cmd.commands[0], "Unsupported: 'diff' "
+                                     "cannot be part of a pipeline")
+        executeBuiltinDiff(cmd.commands[0])
+        return 0
+
+    if cmd.commands[0].args[0] == 'rm':
+        if len(cmd.commands) != 1:
+            raise InternalShellError(cmd.commands[0], "Unsupported: 'rm' "
+                                     "cannot be part of a pipeline")
+        executeBuiltinRm(cmd.commands[0], shenv)
+        return 0
+
     procs = []
     default_stdin = subprocess.PIPE
     stderrTempFiles = []
Index: lit/tests/Inputs/shtest-shell/diff-error-0.txt
===================================================================
--- /dev/null
+++ lit/tests/Inputs/shtest-shell/diff-error-0.txt
@@ -0,0 +1,3 @@
+# Check error on a unsupported diff (cannot be part of a pipeline).
+#
+# RUN: diff temp1.txt temp2.txt | echo Output
Index: lit/tests/Inputs/shtest-shell/diff-error-1.txt
===================================================================
--- /dev/null
+++ lit/tests/Inputs/shtest-shell/diff-error-1.txt
@@ -0,0 +1,3 @@
+# Check error on a unsupported diff (only supports a fromfile and tofile).
+#
+# RUN: diff -u temp1.txt temp2.txt
Index: lit/tests/Inputs/shtest-shell/diff-error-2.txt
===================================================================
--- /dev/null
+++ lit/tests/Inputs/shtest-shell/diff-error-2.txt
@@ -0,0 +1,3 @@
+# Check error on an internal shell error (missing tofile)
+#
+# RUN: diff temp.txt
Index: lit/tests/Inputs/shtest-shell/diff-error-3.txt
===================================================================
--- /dev/null
+++ lit/tests/Inputs/shtest-shell/diff-error-3.txt
@@ -0,0 +1,3 @@
+# Check error on an internal shell error (unable to find compared files)
+#
+# RUN: diff temp.txt temp1.txt
Index: lit/tests/Inputs/shtest-shell/diff-error-4.txt
===================================================================
--- /dev/null
+++ lit/tests/Inputs/shtest-shell/diff-error-4.txt
@@ -0,0 +1,5 @@
+# Check error on an internal shell error (file's contexts are different)
+#
+# RUN: echo "hello-first" > %t
+# RUN: echo "hello-second" > %t1
+# RUN: diff %t %t1
Index: lit/tests/Inputs/shtest-shell/mkdir-error-0.txt
===================================================================
--- /dev/null
+++ lit/tests/Inputs/shtest-shell/mkdir-error-0.txt
@@ -0,0 +1,3 @@
+# Check error on a unsupported mkdir (cannot be part of a pipeline).
+#
+# RUN: mkdir -p temp | rm -rf temp
Index: lit/tests/Inputs/shtest-shell/mkdir-error-1.txt
===================================================================
--- /dev/null
+++ lit/tests/Inputs/shtest-shell/mkdir-error-1.txt
@@ -0,0 +1,3 @@
+# Check error on a unsupported mkdir (only does not support -i option).
+#
+# RUN: mkdir -i temp
Index: lit/tests/Inputs/shtest-shell/mkdir-error-2.txt
===================================================================
--- /dev/null
+++ lit/tests/Inputs/shtest-shell/mkdir-error-2.txt
@@ -0,0 +1,3 @@
+# Check error on a unsupported mkdir (missing operand).
+#
+# RUN: mkdir -p
Index: lit/tests/Inputs/shtest-shell/rm-error-0.txt
===================================================================
--- /dev/null
+++ lit/tests/Inputs/shtest-shell/rm-error-0.txt
@@ -0,0 +1,3 @@
+# Check error on a unsupported rm. (cannot be part of a pipeline)
+#
+# RUN: rm -rf temp | echo "hello"
Index: lit/tests/Inputs/shtest-shell/rm-error-1.txt
===================================================================
--- /dev/null
+++ lit/tests/Inputs/shtest-shell/rm-error-1.txt
@@ -0,0 +1,3 @@
+# Check error on a unsupported rm (only does not support -i option).
+#
+# RUN: rm -f -i temp
Index: lit/tests/Inputs/shtest-shell/rm-error-2.txt
===================================================================
--- /dev/null
+++ lit/tests/Inputs/shtest-shell/rm-error-2.txt
@@ -0,0 +1,3 @@
+# Check error on a unsupported rm (only supports -f option and in combination with -r).
+#
+# RUN: rm -r hello
Index: lit/tests/Inputs/shtest-shell/rm-error-3.txt
===================================================================
--- /dev/null
+++ lit/tests/Inputs/shtest-shell/rm-error-3.txt
@@ -0,0 +1,4 @@
+# Check error on a unsupported rm (can't remove test since it is a directory).
+#
+# RUN: mkdir -p test
+# RUN: rm -f test
Index: lit/tests/Inputs/shtest-shell/valid-shell.txt
===================================================================
--- /dev/null
+++ lit/tests/Inputs/shtest-shell/valid-shell.txt
@@ -0,0 +1,26 @@
+# Check mkdir and rm operations.
+#
+# RUN: rm -f -r %T/test
+# RUN: mkdir -p %T/test
+# RUN: cd %T/test
+# RUN: rm -rf test1
+# RUN: mkdir test1
+# RUN: cd test1
+# RUN: rm -rf %T/test1 %T/test2 %T/test3
+# RUN: mkdir -p %T/test1 %T/test2 %T/test3
+# RUN: cd %T/test1
+# RUN: cd %T/test2
+# RUN: cd %T/test3
+
+# Check diff operations.
+#
+# RUN: echo "hello" > %t
+# RUN: echo "hello" > %t1
+# RUN: diff %t %t1
+
+# Check rm operations.
+#
+# RUN: rm -f %T/test/temp.txt
+# RUN: rm -fr %T/test
+# RUN: rm -f %T/test.txt
+# RUN: rm -r -f %T/*
Index: lit/tests/max-failures.py
===================================================================
--- lit/tests/max-failures.py
+++ lit/tests/max-failures.py
@@ -8,7 +8,7 @@
 #
 # END.
 
-# CHECK: Failing Tests (3)
+# CHECK: Failing Tests (15)
 # CHECK: Failing Tests (1)
 # CHECK: Failing Tests (2)
 # CHECK: error: Setting --max-failures to 0 does not have any effect.
Index: lit/tests/shtest-shell.py
===================================================================
--- lit/tests/shtest-shell.py
+++ lit/tests/shtest-shell.py
@@ -10,6 +10,47 @@
 
 # CHECK: -- Testing:
 
+
+# CHECK: FAIL: shtest-shell :: diff-error-0.txt
+# CHECK: *** TEST 'shtest-shell :: diff-error-0.txt' FAILED ***
+# CHECK: $ "diff" "temp1.txt" "temp2.txt"
+# CHECK: # command stderr:
+# CHECK: Unsupported: 'diff' cannot be part of a pipeline
+# CHECK: error: command failed with exit status: 127
+# CHECK: ***
+
+# CHECK: FAIL: shtest-shell :: diff-error-1.txt
+# CHECK: *** TEST 'shtest-shell :: diff-error-1.txt' FAILED ***
+# CHECK: $ "diff" "-u" "temp1.txt" "temp2.txt"
+# CHECK: # command stderr:
+# CHECK: Error: 'diff' only supports a fromfile and tofile
+# CHECK: error: command failed with exit status: 127
+# CHECK: ***
+
+# CHECK: FAIL: shtest-shell :: diff-error-2.txt
+# CHECK: *** TEST 'shtest-shell :: diff-error-2.txt' FAILED ***
+# CHECK: $ "diff" "temp.txt"
+# CHECK: # command stderr:
+# CHECK: Error: 'diff' only supports a fromfile and tofile
+# CHECK: error: command failed with exit status: 127
+# CHECK: ***
+
+# CHECK: FAIL: shtest-shell :: diff-error-3.txt
+# CHECK: *** TEST 'shtest-shell :: diff-error-3.txt' FAILED ***
+# CHECK: $ "diff" "temp.txt" "temp1.txt"
+# CHECK: # command stderr:
+# CHECK: Error: 'diff' command failed
+# CHECK: error: command failed with exit status: 127
+# CHECK: ***
+
+# CHECK: FAIL: shtest-shell :: diff-error-4.txt
+# CHECK: *** TEST 'shtest-shell :: diff-error-4.txt' FAILED ***
+# CHECK: $ "diff"
+# CHECK: # command stderr:
+# CHECK: Error: The contexts of fromfile and tofile are different
+# CHECK: error: command failed with exit status: 127
+# CHECK: ***
+
 # CHECK: FAIL: shtest-shell :: error-0.txt
 # CHECK: *** TEST 'shtest-shell :: error-0.txt' FAILED ***
 # CHECK: $ "not-a-real-command"
@@ -30,7 +71,65 @@
 # CHECK: Unsupported redirect:
 # CHECK: ***
 
+# CHECK: FAIL: shtest-shell :: mkdir-error-0.txt
+# CHECK: *** TEST 'shtest-shell :: mkdir-error-0.txt' FAILED ***
+# CHECK: $ "mkdir" "-p" "temp"
+# CHECK: # command stderr:
+# CHECK: Unsupported: 'mkdir' cannot be part of a pipeline
+# CHECK: error: command failed with exit status: 127
+# CHECK: ***
+
+# CHECK: FAIL: shtest-shell :: mkdir-error-1.txt
+# CHECK: *** TEST 'shtest-shell :: mkdir-error-1.txt' FAILED ***
+# CHECK: $ "mkdir" "-i" "temp"
+# CHECK: # command stderr:
+# CHECK: Unsupported: 'mkdir' does not support -i option
+# CHECK: error: command failed with exit status: 127
+# CHECK: ***
+
+# CHECK: FAIL: shtest-shell :: mkdir-error-2.txt
+# CHECK: *** TEST 'shtest-shell :: mkdir-error-2.txt' FAILED ***
+# CHECK: $ "mkdir" "-p"
+# CHECK: # command stderr:
+# CHECK: Error: 'mkdir' is missing an operand
+# CHECK: error: command failed with exit status: 127
+# CHECK: ***
+
 # CHECK: PASS: shtest-shell :: redirects.txt
+
+# CHECK: FAIL: shtest-shell :: rm-error-0.txt
+# CHECK: *** TEST 'shtest-shell :: rm-error-0.txt' FAILED ***
+# CHECK: $ "rm" "-rf" "temp"
+# CHECK: # command stderr:
+# CHECK: Unsupported: 'rm' cannot be part of a pipeline
+# CHECK: error: command failed with exit status: 127
+# CHECK: ***
+
+# CHECK: FAIL: shtest-shell :: rm-error-1.txt
+# CHECK: *** TEST 'shtest-shell :: rm-error-1.txt' FAILED ***
+# CHECK: $ "rm" "-f" "-i" "temp"
+# CHECK: # command stderr:
+# CHECK: Unsupported: 'rm' does not support -i option
+# CHECK: error: command failed with exit status: 127
+# CHECK: ***
+
+# CHECK: FAIL: shtest-shell :: rm-error-2.txt
+# CHECK: *** TEST 'shtest-shell :: rm-error-2.txt' FAILED ***
+# CHECK: $ "rm" "-r" "hello"
+# CHECK: # command stderr:
+# CHECK: Error: 'rm' command failed
+# CHECK: error: command failed with exit status: 127
+# CHECK: ***
+
+# CHECK: FAIL: shtest-shell :: rm-error-3.txt
+# CHECK: *** TEST 'shtest-shell :: rm-error-3.txt' FAILED ***
+# CHECK: $ "rm" "-f" "test"
+# CHECK: # command stderr:
+# CHECK: Error: test is a directory
+# CHECK: error: command failed with exit status: 127
+# CHECK: ***
+
 # CHECK: PASS: shtest-shell :: sequencing-0.txt
 # CHECK: XFAIL: shtest-shell :: sequencing-1.txt
-# CHECK: Failing Tests (3)
+# CHECK: PASS: shtest-shell :: valid-shell.txt
+# CHECK: Failing Tests (15)