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utils-std

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

which.c (2218B)

    

  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. #define _POSIX_C_SOURCE 200809L
  6. #include "../lib/getopt_nolong.h"
  7. #include "../lib/strchrnul.h"
  9. #include <errno.h>
  10. #include <limits.h> // PATH_MAX
  11. #include <stdbool.h>
  12. #include <stdio.h>  // fprintf
  13. #include <stdlib.h> // getenv
  14. #include <string.h> // strcpy, memcpy
  15. #include <unistd.h> // access, getopt
  17. const char *argv0 = "which";
  19. int
  20. main(int argc, char *argv[])
  21. {
  22. 	bool opt_a = false, opt_s = false;
  23. 	int missing = 0;
  25. 	char *path = getenv("PATH");
  26. 	if(path == NULL)
  27. 	{
  28. 		fputs("which: error: $PATH environment unset", stderr);
  29. 		return 1;
  30. 	}
  32. 	for(int c = -1; (c = getopt_nolong(argc, argv, "as")) != -1;)
  33. 	{
  34. 		switch(c)
  35. 		{
  36. 		case 'a':
  37. 			opt_a = true;
  38. 			break;
  39. 		case 's':
  40. 			opt_s = true;
  41. 			break;
  42. 		case '?':
  43. 			GETOPT_UNKNOWN_OPT
  44. 			return 1;
  45. 		default:
  46. 			abort();
  47. 		}
  48. 	}
  50. 	argc -= optind;
  51. 	argv += optind;
  53. 	if(argc <= 0) return 1;
  55. 	for(int i = 0; i < argc; i++)
  56. 	{
  57. 		char *cmd = argv[i];
  58. 		size_t cmdlen = strlen(cmd);
  59. 		bool found = false;
  60. 		char *start = path;
  62. 		const char *prev = start;
  63. 		while(true)
  64. 		{
  65. 			static char buf[PATH_MAX] = "";
  66. 			const char *stop = utils_strchrnul(prev, ':');
  68. 			size_t buflen = stop - prev;
  69. 			memcpy(buf, prev, buflen);
  71. 			if((PATH_MAX - buflen - 1) < cmdlen)
  72. 			{
  73. 				buf[buflen] = '\0';
  74. 				fprintf(stderr,
  75. 				        "which: warning: Concatenation of PATH element '%s' and command '%s' would be "
  76. 				        "greater than PATH_MAX\n",
  77. 				        buf,
  78. 				        cmd);
  79. 				goto which_cont;
  80. 			}
  82. 			buf[buflen++] = '/';
  84. 			memcpy(buf + buflen, cmd, cmdlen);
  85. 			buflen += cmdlen;
  86. 			buf[buflen] = '\0';
  88. 			errno = 0;
  89. 			if(access(buf, X_OK) == 0)
  90. 			{
  91. 				if(!opt_s) puts(buf);
  93. 				found = true;
  95. 				if(!opt_a) break;
  96. 			}
  98. 			switch(errno)
  99. 			{
  100. 			case ENOENT:
  101. 			case 0:
  102. 				break;
  103. 			default:
  104. 				fprintf(stderr,
  105. 				        "which: warning: Failed checking access on file '%s': %s\n",
  106. 				        buf,
  107. 				        strerror(errno));
  108. 				break;
  109. 			}
  111. 		which_cont:
  112. 			if(*stop == '\0') break;
  113. 			prev = stop + 1;
  114. 		}
  116. 		if(!found) missing++;
  117. 	}
  119. 	return missing;
  120. }