invoking suprograms at lower priority

[gtoal]

You mentioned in another thread (which has followups cut off as it is over 3 months old) that you would like to invoke the subprocesses with a lower priority. I hacked up the utility below for myself just now for some other project, but had Crunchie in mind as a potential application while I was writing it. Should be easy to add in:

// Compiled on Windows using the free compiler, LCC.  Should work with
// most other Windows-based C compilers too.

// See:
//       http://xona.com/2004/07/22.html
//       http://episteme.arstechnica.com/groupee/forums/a/tpc/f/99609816/m/365007825731/inc/-1
//       http://www.jpsoft.com/help/index.htm?start.htm
//              (and http://www.jpsoft.com/help/index.htm?detach.htm )

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>

// Windows uses the wrong name:
#define strcasecmp stricmp

// procedure does not print any error messages, allowing us to
// invoke it both from command-line code and from GUI code.

// Error conditions not extensively tested.

int priosystem(char *exefile, char *process_name, char *priority) {
#define SLOP 32
  char *formatstr = "%s /c start \"%s\" /%s \"%s\"";
  char *allowed[] = {
    "Realtime", "High", "AboveNormal", "Normal", "BelowNormal", "Low",
    NULL
  };
  char *command, *comspec;
  int prio = 0;
  int rc; // result of system() call.

  // priority: Realtime, High, AboveNormal, Normal, BelowNormal, Low.
  //           24        13    10           8       6            4
  for (;;) {
    if (allowed[prio] == NULL) {
      // programmer error
      return -2; // BAD PRIORITY STRING
    }
    if (strcasecmp(priority, allowed[prio]) == 0) break;
    prio += 1;
  }

  {
    FILE *test;
    int c;

    comspec = getenv("ComSpec");
    if (comspec == NULL) {
      // relatively safe fallback
      comspec = "C:\\WINDOWS\\system32\\cmd.exe"; // DO NOT "free(comspec)"!
    }
    test = fopen(comspec, "rb");
    if (test == NULL) {
      return -3; // BAD COMMAND INTERPRETER - no %COMSPEC%, no C:...
    }
    c = fgetc(test);
    if (c == EOF || ferror(test)) {
      fclose(test);
      return -4; // BAD COMMAND INTERPRETER FILE?
    }
    fclose(test);
  }

  command = malloc(strlen(formatstr) +
                   strlen(exefile) +
                   strlen(process_name) +
                   strlen(priority) +
                   SLOP);

  if (command == NULL) {
    // you're screwed.  Probably even a printf will fail if we have this little RAM left.
    return -1; // GROSSLY INSUFFICIENT MEMORY
  }


  // NOTE: as with system(), using this command makes you vulnerable to
  // data injection hacks, if someone supplies a bad parameter or messes with COMSPEC
  // So use only when the parameters are under you control.

  sprintf(command, formatstr,
          comspec,
          process_name,
          allowed[prio],
          exefile);
  rc = system(command);
  free(command);
  return rc;
#undef SLOP
}

#ifdef PRIOTEST_MAIN
int main(int argc, char **argv)
{
  int rc;
  fprintf(stderr, "TEST STARTING\n"); fflush(stderr);
  rc = priosystem("notepad.exe", "Notepad (Low prio)", "belownormal");
  fprintf(stderr, "SYSTEM RETURNS\n"); fflush(stderr);
  switch (rc) {
  case 0:  break;
  case -1: // no memory at all
      fprintf(stderr, "FATAL: no mem\n"); exit(1);
  case -2: // bad prio string
      fprintf(stderr, "Error: bad priority string\n"); exit(2);
  case -3: // bad CLI or no comspec
      fprintf(stderr, "Failure: cannot determine which CMD.EXE to use\n"); exit(3);
  case -4: // bad CLI
      fprintf(stderr, "Failure: CMD.EXE bad perms or file corrupt - %s\n", strerror(errno));
      exit(4);
  default:
      fprintf(stderr, "Failure: %s\n", strerror(errno));
  }
  exit(0);
  /* NOT REACHED */
  return 1;
}
#endif

[arkay]

gtoal,

Thanks I already know how to specify priorities in Crunchie though. The only reason it isn't done is cause I need to change the entire code to a multithreaded model where not only can I control the priority but also monitor and kill hung processes etc. (As well as use gui components, status bars etc).

The above is a good idea though You could probably replace both mencoder and dvrmstompeg.exe with batch files that call the above code to then execute the real executables.. Thereby giving you the lower priorites without any changes required for Crunchie.

Cheers,
Arkay.

Cheers,
Arkay.