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

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}"