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| author | walimis <walimisdev@gmail.com> | 2008-11-28 12:21:19 +0800 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2008-11-28 13:15:14 +0100 |
| commit | c072c24975ec4f0ccfcb6f5c8a8040b6eb75ef8f (patch) | |
| tree | 39d5e69fa5a7c98b71c103d7f4e0f7318215ddae /Documentation/ftrace.txt | |
| parent | 50cdaf08a8ec1d7f43987705da7aff7cf949708f (diff) | |
| download | lwn-c072c24975ec4f0ccfcb6f5c8a8040b6eb75ef8f.tar.gz lwn-c072c24975ec4f0ccfcb6f5c8a8040b6eb75ef8f.zip | |
ftrace: improve documentation
Impact: extend documentation with notice of using wild cards correctly
We know that we can use wild cards to set set_ftrace_filter, but there's
problem when using them naively 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 filenames to set_ftrace_filter, not the
intended "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 escape 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.
Signed-off-by: walimis <walimisdev@gmail.com>
Acked-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'Documentation/ftrace.txt')
| -rw-r--r-- | Documentation/ftrace.txt | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/Documentation/ftrace.txt b/Documentation/ftrace.txt index de05042f11b9..803b1318b13d 100644 --- a/Documentation/ftrace.txt +++ b/Documentation/ftrace.txt @@ -1251,7 +1251,11 @@ These are the only wild cards which are supported. <match>*<match> will not work. - # echo hrtimer_* > /debug/tracing/set_ftrace_filter +Note: It is better to use quotes to enclose the wild cards, otherwise + the shell may expand the parameters into names of files in the local + directory. + + # echo 'hrtimer_*' > /debug/tracing/set_ftrace_filter Produces: @@ -1306,7 +1310,7 @@ Again, now we want to append. # echo sys_nanosleep > /debug/tracing/set_ftrace_filter # cat /debug/tracing/set_ftrace_filter sys_nanosleep - # echo hrtimer_* >> /debug/tracing/set_ftrace_filter + # echo 'hrtimer_*' >> /debug/tracing/set_ftrace_filter # cat /debug/tracing/set_ftrace_filter hrtimer_run_queues hrtimer_run_pending |