进程或程序正在执行的系统调用的类型

Question

I am trying to find how many different type of syscalls a process or program is making. I know that I can do following to get total number of calls for each syscall as below.

strace -c cat abc.txt

The output of above is command.

% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
  -nan    0.000000           0        10           read
  -nan    0.000000           0         1           write
  -nan    0.000000           0        12           open
  -nan    0.000000           0        14           close
  -nan    0.000000           0        12           fstat
  -nan    0.000000           0        28           mmap
  -nan    0.000000           0        16           mprotect
  -nan    0.000000           0         3           munmap
  -nan    0.000000           0         3           brk
  -nan    0.000000           0         2           rt_sigaction
  -nan    0.000000           0         1           rt_sigprocmask
  -nan    0.000000           0         2           ioctl
  -nan    0.000000           0         1         1 access
  -nan    0.000000           0         1           execve
  -nan    0.000000           0         1           fcntl
  -nan    0.000000           0         2           getdents
  -nan    0.000000           0         1           getrlimit
  -nan    0.000000           0         1           statfs
  -nan    0.000000           0         1           arch_prctl
  -nan    0.000000           0         2         1 futex
  -nan    0.000000           0         1           set_tid_address
  -nan    0.000000           0         1           set_robust_list
------ ----------- ----------- --------- --------- ----------------
100.00    0.000000                   116         2 total

As you can see that it returns the total number of syscalls made which is 116 . I only need to know how many different type syscalls were made which is 22 in this case.

Is there a way to do that in one line using strace ?

Answer 1

Pipe the output to wc -l to get the number of lines in the statistics. Since the statistics are written to standard error, you'll need to do some redirection for this.

strace -c cat abc.txt 2>&1 >/dev/null | wc -l

You'll also need to subtract 4 from this, because of the header, total, and divider lines.