diff --git a/tools/autopep8.sh b/tools/autopep8.sh
index 44e6f1ac1a9..e489627a914 100755
--- a/tools/autopep8.sh
+++ b/tools/autopep8.sh
@@ -71,8 +71,18 @@ function main() {
   # Keep this list of Python extensions the same with the list of
   # extensions searched for in the tools/git/pre-commit hook.
   grep -E '\.py$|\.cli.ext$|\.test.ext$' ${files} > ${files_filtered}
+  # Prepend the filenames with "./" to make the modified file output consistent
+  # with the clang-format target output.
+  sed -i'.bak' 's:^:\./:' ${files_filtered}
+  rm -f ${files_filtered}.bak
 
-  echo "Running autopep8. This may take a minute."
+  # Efficiently retrieving modification timestamps in a platform
+  # independent way is challenging. We use find's -newer argument, which
+  # seems to be broadly supported. The following file is created and has a
+  # timestamp just before running clang-format. Any file with a timestamp
+  # after this we assume was modified by clang-format.
+  start_time_file=${tmp_dir}/format_start.$$
+  touch ${start_time_file}
   autopep8 \
       --ignore-local-config \
       -i \
@@ -82,8 +92,11 @@ function main() {
       --aggressive \
       --aggressive \
       $(cat ${files_filtered})
+  find $(cat ${files_filtered}) -newer ${start_time_file}
+
   # The above will not catch the Python files in the metalink tests because
   # they do not have extensions.
+  metalink_dir=${DIR}/plugins/experimental/metalink/test
   autopep8 \
       --ignore-local-config \
       -i \
@@ -93,8 +106,8 @@ function main() {
       --aggressive \
       --aggressive \
       --recursive \
-      ${DIR}/plugins/experimental/metalink/test
-  echo "autopep8 completed."
+      ${metalink_dir}
+  find ${metalink_dir} -newer ${start_time_file}
   rm -rf ${tmp_dir}
   deactivate
 }
diff --git a/tools/clang-format.sh b/tools/clang-format.sh
index c85a5965c4c..eb142b6b95f 100755
--- a/tools/clang-format.sh
+++ b/tools/clang-format.sh
@@ -87,7 +87,17 @@ EOF
       exit 1
   else
       [ ${just_install} -eq 1 ] && return
-      for file in $(find $DIR -iname \*.[ch] -o -iname \*.cc -o -iname \*.h.in); do
+
+      # Efficiently retrieving modification timestamps in a platform
+      # independent way is challenging. We use find's -newer argument, which
+      # seems to be broadly supported. The following file is created and has a
+      # timestamp just before running clang-format. Any file with a timestamp
+      # after this we assume was modified by clang-format.
+      start_time_file=$(mktemp -t clang-format-start-time.XXXXXXXXXX)
+      touch ${start_time_file}
+
+      target_files=$(find $DIR -iname \*.[ch] -o -iname \*.cc -o -iname \*.h.in)
+      for file in ${target_files}; do
         # The ink_autoconf.h and ink_autoconf.h.in files are generated files,
         # so they do not need to be re-formatted by clang-format. Doing so
         # results in make rebuilding all our files, so we skip formatting them
@@ -95,9 +105,11 @@ EOF
         base_name=$(basename ${file})
         [ ${base_name} = 'ink_autoconf.h.in' -o ${base_name} = 'ink_autoconf.h' ] && continue
 
-        echo $file
         ${FORMAT} -i $file
       done
+
+      find ${target_files} -newer ${start_time_file}
+      rm ${start_time_file}
   fi
 }