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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
  9. // Sadly {Free,Net}BSD hides _SC_NPROCESSORS_{CONF,ONLN} if _POSIX_C_SOURCE is defined *sigh*
  10. // #define _POSIX_C_SOURCE 202405L
  12. #include <errno.h>
  13. #include <stdio.h>  // printf
  14. #include <string.h> // strerror
  15. #include <unistd.h> // sysconf, getopt, opt*
  17. const char *argv0 = "nproc";
  19. static void
  20. usage(void)
  21. {
  22. 	fprintf(stderr, "Usage: nproc [-a]\n");
  23. }
  25. int
  26. main(int argc, char *argv[])
  27. {
  28. 	// currently available
  29. 	int target = _SC_NPROCESSORS_ONLN;
  30. 	const char *target_str = "_SC_NPROCESSORS_ONLN";
  32. 	for(int c = -1; (c = getopt(argc, argv, ":a")) != -1;)
  33. 	{
  34. 		switch(c)
  35. 		{
  36. 		case 'a': // can be made available
  37. 			target = _SC_NPROCESSORS_CONF;
  38. 			target_str = "_SC_NPROCESSORS_CONF";
  39. 			break;
  40. 		case ':':
  41. 			fprintf(stderr, "%s: error: Missing operand for option: '-%c'\n", argv0, optopt);
  42. 			usage();
  43. 			return 1;
  44. 		case '?':
  45. 			fprintf(stderr, "%s: error: Unrecognised option: '-%c'\n", argv0, optopt);
  46. 			usage();
  47. 			return 1;
  48. 		}
  49. 	}
  51. 	long np = sysconf(target);
  52. 	if(np < 0)
  53. 	{
  54. 		fprintf(
  55. 		    stderr, "%s: error: Failed getting sysconf '%s': %s\n", argv0, target_str, strerror(errno));
  56. 		return 1;
  57. 	}
  59. 	printf("%ld\n", np);
  61. 	return 0;
  62. }