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utils-std

Collection of commonly available Unix tools git clone https://anongit.hacktivis.me/git/utils-std.git

nproc.c (1480B)

    

  1. // utils-std: Collection of commonly available Unix tools
  2. // SPDX-FileCopyrightText: 2017 Haelwenn (lanodan) Monnier <contact+utils@hacktivis.me>
  3. // SPDX-License-Identifier: MPL-2.0
  5. // _SC_NPROCESSORS_CONF &_SC_NPROCESSORS_ONLN got added in POSIX.1-2024
  6. // https://www.austingroupbugs.net/view.php?id=339
  7. #define _DEFAULT_SOURCE
  8. // Sadly {Free,Net}BSD hides _SC_NPROCESSORS_{CONF,ONLN} if _POSIX_C_SOURCE is defined *sigh*
  9. // #define _POSIX_C_SOURCE 202405L
  10. #include <errno.h>
  11. #include <stdio.h>  // printf
  12. #include <string.h> // strerror
  13. #include <unistd.h> // sysconf, getopt, opt*
  15. const char *argv0 = "nproc";
  17. static void
  18. usage(void)
  19. {
  20. 	fprintf(stderr, "Usage: nproc [-a]\n");
  21. }
  23. int
  24. main(int argc, char *argv[])
  25. {
  26. 	// currently available
  27. 	int target = _SC_NPROCESSORS_ONLN;
  28. 	const char *target_str = "_SC_NPROCESSORS_ONLN";
  30. 	int c = -1;
  31. 	while((c = getopt(argc, argv, ":a")) != -1)
  32. 	{
  33. 		switch(c)
  34. 		{
  35. 		case 'a': // can be made available
  36. 			target = _SC_NPROCESSORS_CONF;
  37. 			target_str = "_SC_NPROCESSORS_CONF";
  38. 			break;
  39. 		case ':':
  40. 			fprintf(stderr, "%s: error: Missing operand for option: '-%c'\n", argv0, optopt);
  41. 			usage();
  42. 			return 1;
  43. 		case '?':
  44. 			fprintf(stderr, "%s: error: Unrecognised option: '-%c'\n", argv0, optopt);
  45. 			usage();
  46. 			return 1;
  47. 		}
  48. 	}
  50. 	long np = sysconf(target);
  51. 	if(np < 0)
  52. 	{
  53. 		fprintf(
  54. 		    stderr, "%s: error: Failed getting sysconf '%s': %s\n", argv0, target_str, strerror(errno));
  55. 		return 1;
  56. 	}
  58. 	printf("%ld\n", np);
  60. 	return 0;
  61. }