[PATCH V2] tools: rcu: Added check for argument and usage function

[Bhaskar Chowdhury <unixbhaskar@gmail.com>]

Thought it would be good to have some formatted way of letting user know
about, how to use this script properly and added some checking too for missing
argument.


cc: paulmck@kernel.org

Signed-off-by: Bhaskar Chowdhury <unixbhaskar@gmail.com>
---
 Changes from V1 : Flip the code blocks of function for logical evaluation
                   and strip off the path from script when displaying help
 tools/rcu/extract-stall.sh | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/tools/rcu/extract-stall.sh b/tools/rcu/extract-stall.sh
index e565697c9f90..6ea76230f72f 100644
--- a/tools/rcu/extract-stall.sh
+++ b/tools/rcu/extract-stall.sh
@@ -1,11 +1,24 @@
 #!/bin/sh
 # SPDX-License-Identifier: GPL-2.0+
 #
-# Extract any RCU CPU stall warnings present in specified file.
-# Filter out clocksource lines.  Note that preceding-lines excludes the
-# initial line of the stall warning but trailing-lines includes it.
-#
-# Usage: extract-stall.sh dmesg-file [ preceding-lines [ trailing-lines ] ]
+# This is a usage function to spit out information about properly use this
+# script
+
+usage() {
+
+   echo  Extract any RCU CPU stall warnings present in specified file.
+   echo  Filter out clocksource lines.  Note that preceding-lines excludes the
+   echo  initial line of the stall warning but trailing-lines includes it.
+
+   echo Usage: $(basename $0) dmesg-file [ preceding-lines [ trailing-lines ] ]
+}
+
+# Terminate the script, if the argument is missing
+
+if [ $# -eq 0 ];then
+	usage
+	exit 1
+fi

 echo $1
 preceding_lines="${2-3}"
--
2.38.2