Use the $target macro variable to create scripts that can be applied to a particular user process of interest that is selected on the dtrace command line using the p option or created using the c option. The D programs specified on the command line or using the s option are compiled after processes are created or grabbed and the $target variable expands to the integer process-ID of the first such process. For example, the following D script could be used to determine the distribution of system calls executed by a particular subject process:

syscall:::entry
/pid == $target/
{
	@[probefunc] = count();
}

To determine the number of system calls executed by the date ( 1 ) command, save the script in the file syscall.d and execute the following command:

# dtrace -s syscall.d -c date
dtrace: script 'syscall.d' matched 227 probes
Fri Jul 30 13:46:06 PDT 2004
dtrace: pid 109058 has exited

  gtime                                                             1
  getpid                                                            1
  getrlimit                                                         1
  rexit                                                             1
  ioctl                                                             1
  resolvepath                                                       1
  read                                                              1
  stat                                                              1
  write                                                             1
  munmap                                                            1
  close                                                             2
  fstat64                                                           2
  setcontext                                                        2
  mmap                                                              2
  open                                                              2
  brk                                                               4