> > Hi all, > > > > I'm new to ftrace and linux programming in general. Forgive me for > > Hi Lin, > > Welcome! > > > asking dumb questions. > > When first learning something, there are no dumb questions :-) Thank you, Steve. > trace-cmd is hard to read, but we are working on sample code that will make > using libtracefs much easier. For example, I wrote this simple code to read > all files that are opened. I will check out the example, and keep digging in trace-cmd. Thanks, -Lin On Wed, May 5, 2021 at 9:18 AM Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > > On Wed, 5 May 2021 08:21:35 -0400 > Lin Wang <wanglinseven@xxxxxxxxx> wrote: > > > Hi all, > > > > I'm new to ftrace and linux programming in general. Forgive me for > > Hi Lin, > > Welcome! > > > asking dumb questions. > > When first learning something, there are no dumb questions :-) > > > > > I'm trying to continuously capture certain kernel events, convert them > > to a different format and then write them to a file. > > > > I understand that trace_pipe should be used for streaming. But I'm not > > sure how to read the content of trace_pipe at event boundary (I > > currently just read it to a temp buffer which would sometimes cut the > > last event in half). I discovered libtraceevent and libtracefs that I > > think are meant to help with this kind of tasks, so I'm reading the > > source code of trace-cmd to find examples. But so far the progress has > > been slow. > > Yes, libtracefs is what you want. > > The man pages are here (I'm still working on a tutorial): > > https://trace-cmd.org/Documentation/libtracefs/libtracefs.html > > Although that may be a little out of date. I need to automate that to be > updated whenever I make a new release. > > > > > Could anyone point me to the right direction, or advise me with a > > general outline of what I should do to achieve my task? > > > > I think you may be on the right track. > > trace-cmd is hard to read, but we are working on sample code that will make > using libtracefs much easier. For example, I wrote this simple code to read > all files that are opened. > > # ./show-open-files cat /etc/passwd > 42727-<...>: file=/etc/ld.so.cache flags=88000 mode=0 > 42727-<...>: : addr=0x7f8900123868 > 42727-<...>: : addr=0x7f89001100f7 > 42727-<...>: file=/lib64/libc.so.6 flags=88000 mode=0 > 42727-<...>: : addr=0x7f8900123868 > 42727-<...>: : addr=0x7f8900110139 > 42727-<...>: file=/usr/lib/locale/locale-archive flags=88000 mode=0 > 42727-<...>: : addr=0x7f890000886c > 42727-<...>: : addr=0x7f88fff448ce > 42727-<...>: : addr=0x7f88fff44268 > root:x:0:0:root:/root:/bin/bash > [..] > flatpak:x:963:962:User for flatpak system helper:/:/sbin/nologin > 42727-<...>: file=/etc/passwd flags=8000 mode=0 > 42727-<...>: : addr=0x7f890000319b > 42727-<...>: : addr=0x4c45485300647773 > > > http://rostedt.org/code/show-open-files.c > > We are adding new API to libtracefs all the time to make it even easier to > access the tracefs file system. Feel free to subscribe to linux-trace-devel > if you want to participate or just want to see what is being worked on. > > http://vger.kernel.org/vger-lists.html#linux-trace-devel > > If you have any more questions, feel free to ask! > > -- Steve
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