linux-kernel - Re: about use wild cards for set_ftrace

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Message-ID: <20081127155047.GB24616@ubuntu.mshome.net>
Date:	Thu, 27 Nov 2008 23:50:47 +0800
From:	walimis <walimisdev@...il.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: about use wild cards for set_ftrace_filter and so on

On Thu, Nov 27, 2008 at 10:34:19AM -0500, Steven Rostedt wrote:
>
>On Thu, 27 Nov 2008, walimis wrote:
>
>> 
>> I encountered an issue when using ftrace.
>> We know that we can use wild cards to set set_ftrace_filter, but there's 
>> problem when using such as "echo h* > /debug/tracing/set_ftrace_filter".
>> If there are files named with "h" prefix in current directory, echo "h*" 
>> will echo these files' name to set_ftrace_filter, not "h*".
>> For example:
>> 
>> #cat /debug/tracing/available_filter_functions |grep ^hr |wc -l
>> 23
>> #ls
>> #touch hraa hrdd
>> #ls 
>> hraa  hrdd
>> #echo hr* > /debug/tracing/set_ftrace_filter
>> #cat /debug/tracing/set_ftrace_filter
>> 
>> No output in /debug/tracing/set_ftrace_filter!
>> If we use "" to enclose wild cards, it works:
>> 
>> #ls 
>> hraa  hrdd
>> #echo "hr*" > /debug/tracing/set_ftrace_filter
>> #cat /debug/tracing/set_ftrace_filter |wc -l 
>> 23
>> 
>> This problem can lead to unexpected result if current directory has a 
>> lot of files.
>> I suppose that we can add some notes to document, so a patch attached.
>
>Using TB? It's best to inline the patch, that way I can comment on it 
>better.
Using mutt, but I don't know how to inline the patch now.

>
>Anyway, you should fix the example. I also recommend a single quote over 
>double, to prevent any other translation that bash might do.
>
>The example in ftrace.txt should be:
>
> # echo 'hrtimer_*' > /debug/tracing/set_ftrace_filter
>
>
>Thanks,
>
>-- Steve
>
>/me goes back to eating turkeys.
I only add a note, but I wonder whether enough.
If needed, I can add a example to this document.

Impact: imporve document

Signed-off-by: walimis <walimisdev@...il.com>
---
 Documentation/ftrace.txt |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/Documentation/ftrace.txt b/Documentation/ftrace.txt
index de05042..9735434 100644
--- a/Documentation/ftrace.txt
+++ b/Documentation/ftrace.txt
@@ -1251,6 +1251,9 @@ These are the only wild cards which are supported.
 
   <match>*<match> will not work.
 
+Note: you'd better to use '' to enclose wild cards, otherwise in some
+case you can't get the correct result.
+
  # echo hrtimer_* > /debug/tracing/set_ftrace_filter
 
 Produces:
-- 
1.6.0.3

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