From 593e6d361ff419afc56a2a594675b03bfde6e6d0 Mon Sep 17 00:00:00 2001
From: Niko Matsakis <niko@alum.mit.edu>
Date: Tue, 20 Mar 2018 09:48:17 -0400
Subject: [PATCH] make the script give more useful feedback

---
 src/doc/rustc-dev-guide/ci/check_line_lengths.sh | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/src/doc/rustc-dev-guide/ci/check_line_lengths.sh b/src/doc/rustc-dev-guide/ci/check_line_lengths.sh
index b32906da68fe..dc48091c8733 100755
--- a/src/doc/rustc-dev-guide/ci/check_line_lengths.sh
+++ b/src/doc/rustc-dev-guide/ci/check_line_lengths.sh
@@ -1,5 +1,21 @@
 #!/bin/bash
 
+if [ "$1" == "--help" ]; then
+    echo 'Usage:'
+    echo '  MAX_LINE_LENGTH=80' "$0" 'src/**/*.md'
+    exit 1
+fi
+
+if [ "$MAX_LINE_LENGTH" == "" ]; then
+    echo '`MAX_LINE_LENGTH` environment variable not set. Try --help.'
+    exit 1
+fi
+
+if [ "$1" == "" ]; then
+    echo 'No files provided.'
+    exit 1
+fi
+
 echo "Checking line lengths in all source files <= $MAX_LINE_LENGTH chars..."
 
 echo "Offending files and lines:"