/*      Some System Accounting Utilities, with Examples

  Here is a list of some shell commands and library functions
available in Unix for controling and monitoring processes.  Consult
man pages for full details.  This information applies to Solaris and
with minor exceptions to Linux and other Unix variants.


  Shell Commands:

whoami :  prints login name of current user
who :     prints information for all logged-in users
ps :      prints process information. "ps -ecf" will give
          priority classification and other accounting information
time :    use before a command, as in "time ./a.out"  upon completion,
          it will report the user time, system time, real time, and
          cpu utilization used by the process.
nice :    You can be "nice" to other processes by incrementing the
          nice value.  E.g, "nice +5 ./a.out" will decrement the initial
	  process priority by 5 units.
priocntl: priority control on Solaris.  Restricted use by non-administrators.
kill :    kill a process.  To terminate a process, use the "ps" command to
          find the process id number.  For example, if you want to kill
          process 5000, type "kill -9 5000".  Killing the wrong process
          can be costly even when you're not root, so be careful.
& :       Use the & symbol after a command to run the process in the
          background.  For example, "netscape &" will start netscape but
          still give you the command prompt.  "./a.out &; a.out" will start
	  two ./a.out processes concurrently.  The ";" symbol used here
          is just a way to enter multiple commands.



   Library Functions

  The range of library functions is far more numerous than shell
commands.  Be sure to consult the man page (man - a <command>) to find
details on how to use it, and what header files needs to be included.

getlogin :  returns location of string holding user name of current user
getuid : returns a numerical user id
getpid : returns process id number of current process
getppid : returns parent process id of current process
getpriority : returns a number indicating priority of process.
setpriority : sets priority of process (restricted access)
clock :   returns cpu time for process - see example for usage.
times :   uses a struct to return information concerning user and system
          time consumed by a process.


  The following sample program illustrates the use of these commands.
Study it and run it so you can use it in your own programs.  

*/

/* include headers used by library functions: */
#include<stdio.h>
#include<sys/param.h>
#include<sys/types.h>
#include<sys/times.h>
#include<limits.h>
#include<sys/resource.h>
#include<unistd.h>

int main(int argc, char* argv[])
{
  int i,j, priority;
  struct tms timings;  // used by times
  double cputime;      // store value returned by clock
  pid_t procid, parentid;  // process id and parent process id

  clock();   // start clock for process
  
  for(i=0;i<200000;i++) { printf("%s%d ",argv[1],i); }

  times(&timings);

  cputime = ((double)clock())/CLOCKS_PER_SEC;
  
  printf("CLK_TCK (clock tick) unit value == 1/%d second\n",CLK_TCK);
  printf("User time (in clock ticks) == %d\n",timings.tms_utime);
  printf("System Call time (in clock ticks) == %d\n",timings.tms_stime);
  printf("Total CPU time == %.2f seconds\n",cputime);

  procid = getpid();
  parentid = getppid();
  priority = getpriority(PRIO_PROCESS,procid);
  printf("\nProcess id == %d\n",procid);
  printf("Parent id == %d\n",parentid);
  printf("Process priority == %d\n",priority);
  printf("Current user is %s\n",getlogin());
  printf("Calling user id == %d\n",getuid());

  exit(0);
}


/* Compile and run this program in Solaris tcsh with:

  gcc cguide2.c
  time ./a.out A
  ./a./out A &; nice +5 ./a.out B

  What do the figures tell you?
*/