I want to debug like:

strace -fe open python /usr/bin/gnome-tweak-tool 2>>/tmp/hello.log

strace -fe open python /usr/bin/gnome-tweak-tool 2>>/tmp/hello2.log

Then use kdiff3 to compare both logs, but different pids will make this comparison useless: enter image description here

So my question is there any option from strace to exclude such -f pid ?

2 Answers 2


One could log the outputs of the different pids to different files via the -ff -o filename options:

strace -o foo -ff -e open  perl -e fork
strace -o bar -ff -e open  perl -e fork

and then compare the appropriate foo.<pidnum> and bar.<pidnum> files.

  • A side note, cat bar* > mybar && cat foo* > myfoo && kdiff3 mybar myfoo to compare in one step.
    – 林果皞
    May 9, 2016 at 19:36
sed -r -e 's/^(.+)pid [0-9]+(.+)$/\1pid-xxxx\2/;' -i /tmp/hello2.log

or filter it same way from output.

  • I don't get what should be replace for this pid-xxxx. Empty output when i run sed -r -e 's/pid-[0-9]+/pid-12625/;' -i hello3.log which 12625 is one of the pid in this file. And there are a lot of pids and i need to figure out the unqiue pids one by one?
    – 林果皞
    May 9, 2016 at 16:36
  • @林果皞 ohh, sorry, my bad, test file not like yours. Changed, should work this time.
    – MolbOrg
    May 9, 2016 at 16:42
  • pid-xxxx is just any token, you may set it to empty, just something equal for both files - it will make diff happy
    – MolbOrg
    May 9, 2016 at 16:47
  • The hello3.log doesn't change(should i expect [pid 12606] +++ exited with 0 +++ will shrink to +++ exited with 0 +++ ?) and empty output in terminal when i run sed -r -e 's/^(.+)pid-[0-9]+(.+)$/\1pid-12606\2/;' -i ./hello3.log, my sed version is sed (GNU sed) 4.2.2
    – 林果皞
    May 9, 2016 at 16:53
  • @林果皞 yes definitely, because pid 12606 is't same as pid-12606, sorry again, checked on strace output this time, edited, should work this time. huh.
    – MolbOrg
    May 9, 2016 at 17:03

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