Setting a fixed priority with the setpri subroutine

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An application that runs under the root user ID can use the setpri() subroutine to set its own priority or that of another process.

For example:

retcode = setpri(0,59);

would give the current process a fixed priority of 59. If the setpri() subroutine fails, it returns -1.

The following program accepts a priority value and a list of process IDs and sets the priority of all of the processes to the specified value.

/*
   fixprocpri.c
   Usage: fixprocpri priority PID . . .
*/

#include <sys/sched.h>
#include <stdio.h>
#include <sys/errno.h>

main(int argc,char **argv)
{
   pid_t ProcessID;
   int Priority,ReturnP;

   if( argc < 3 ) {
      printf(" usage - setpri priority pid(s) \n");
      exit(1);
   }

   argv++;
   Priority=atoi(*argv++);
   if ( Priority < 50 ) {
      printf(" Priority must be >= 50 \n");
      exit(1);
   }

   while (*argv) {
      ProcessID=atoi(*argv++);
      ReturnP = setpri(ProcessID, Priority);
      if ( ReturnP > 0 )
          printf("pid=%d new pri=%d  old pri=%d\n",
            (int)ProcessID,Priority,ReturnP);
      else {
          perror(" setpri failed ");
            exit(1);
      }
   }
}