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authorwalimis <walimisdev@gmail.com>2008-11-28 07:21:19 +0300
committerIngo Molnar <mingo@elte.hu>2008-11-28 15:15:14 +0300
commitc072c24975ec4f0ccfcb6f5c8a8040b6eb75ef8f (patch)
tree39d5e69fa5a7c98b71c103d7f4e0f7318215ddae /Documentation/ftrace.txt
parent50cdaf08a8ec1d7f43987705da7aff7cf949708f (diff)
downloadlinux-c072c24975ec4f0ccfcb6f5c8a8040b6eb75ef8f.tar.xz
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.txt8
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