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Date:   Tue, 10 Jan 2023 09:39:09 -0800
From:   "Paul E. McKenney" <paulmck@kernel.org>
To:     Bhaskar Chowdhury <unixbhaskar@gmail.com>
Cc:     linux-kernel@vger.kernel.org
Subject: Re: [PATCH V2] tools: rcu: Added check for argument and usage
 function
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On Tue, Jan 10, 2023 at 04:46:34PM +0530, Bhaskar Chowdhury wrote:
> 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>

Good point on making a usage() function that stands in for the header
comment, thank you!  I tweaked this a bit as shown below, so please
check to see if I messed anything up.

							Thanx, Paul

------------------------------------------------------------------------

commit f4e5cfbdfe900a41375d68b6c83e438ecc519b7b
Author: Bhaskar Chowdhury <unixbhaskar@gmail.com>
Date:   Tue Jan 10 16:46:34 2023 +0530

    tools: rcu: Add usage function and check for argument
    
    This commit converts extract-stall.sh script's header comment to a
    usage() function, and adds an argument check.  While in the area, make
    this script be executable.
    
    [ paulmck: Strength argument check, remove extraneous comment. ]
    
    Signed-off-by: Bhaskar Chowdhury <unixbhaskar@gmail.com>
    Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/tools/rcu/extract-stall.sh b/tools/rcu/extract-stall.sh
old mode 100644
new mode 100755
index e565697c9f90e..08a39ad44320d
--- a/tools/rcu/extract-stall.sh
+++ b/tools/rcu/extract-stall.sh
@@ -1,11 +1,25 @@
 #!/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 ] ]
+
+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
+	echo Usage: $(basename $0) dmesg-file [ preceding-lines [ trailing-lines ] ]
+	echo
+	echo Error: $1
+}
+
+# Terminate the script, if the argument is missing
+
+if test -f "$1" && test -r "$1"
+then
+	:
+else
+	usage "Console log file \"$1\" missing or unreadable."
+	exit 1
+fi
 
 echo $1
 preceding_lines="${2-3}"