How to see system call that executed in current time by process?

Question

Linux utility "strace" show the list of syscall that started after run of strace. How I can see syscall that run in current moment by process? before start of strace.

Answer 1

proc offers some information about what the kernel is currently doing "for" a process
/proc/${pid}/syscall /proc/${pid}/stack

More information:

• http://man7.org/linux/man-pages/man5/proc.5.html
• http://blog.tanelpoder.com/2013/02/21/peeking-into-linux-kernel-land-using-proc-filesystem-for-quickndirty-troubleshooting/