I would like to read /sys/kernel/debug/tracing/trace_pipe in non-blocking way using Linux command-line tools. For instance, cat cannot be used, because it will be blocked. This is similar to this, with the difference that I don't want to use Python.
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I've never heard of a shell command that does this. – Barmar Nov 27 '14 at 02:32
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If you don't want to use Python, how about Perl? – Barmar Nov 27 '14 at 02:33
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I am fine if there's any C language solution. The program should read whatever currently inside `trace_pipe` is and returns. If it is empty, it should immediately quite. – Javad Nov 27 '14 at 03:48
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The concept of ‘non-blocking’ doesn't apply to command-line tools. However, you could run an instance of cat in the background by appending an ampersand to the invocation, like so:
cat /sys/kernel/debug/tracing/trace_pipe &
Now, the command returns immediately, and every time a line is readable from the file, it gets printed to the terminal (and messes up whatever you were typing).
You could also use tail -F if the file itself doesn't block.
user3426575
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This is indeed a solution, however, I would like to sample `trace_pipe` every second. Your approach increases the system load which is undesirable for my use case. – Javad Nov 27 '14 at 03:46
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It's the same as with `cat`: if you want the command to run in the background, add an `&` at the end of the invocation. This shouldn't increase the system load any more than running it the normal way does. – user3426575 Nov 27 '14 at 21:46