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utils-std

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

head.c (6991B)

    

  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
  7. #include "../config.h"
  8. #include "../libutils/fs.h" // auto_fd_copy
  9. #include "../libutils/getopt_nolong.h"
  10. #include "../libutils/truncation.h" // apply_size_suffix
  12. #include <assert.h>
  13. #include <ctype.h> // isdigit
  14. #include <errno.h>
  15. #include <fcntl.h>  // open
  16. #include <stdio.h>  // fprintf, fopen, fread
  17. #include <stdlib.h> // strtoul
  18. #include <string.h> // strerror
  19. #include <unistd.h> // read
  21. static const char *header_fmt = "==> %s <==\n";
  23. const char *argv0 = "head";
  25. ssize_t lines = 10;
  26. size_t bytes = 0;
  28. char *buf = NULL;
  29. size_t buflen = 0;
  31. int delim = '\n';
  33. static int
  34. copy_bytes(const char *filename)
  35. {
  36. 	int fd = -1;
  37. 	if(filename[0] == '-' && filename[1] == 0)
  38. 	{
  39. 		fd = STDIN_FILENO;
  40. 	}
  41. 	else
  42. 	{
  43. 		fd = open(filename, O_RDONLY | O_CLOEXEC | O_NOCTTY);
  44. 		if(fd < 0)
  45. 		{
  46. 			fprintf(
  47. 			    stderr, "%s: error: Failed opening file '%s': %s\n", argv0, filename, strerror(errno));
  48. 			return 1;
  49. 		}
  51. 		posix_fadvise(fd, 0, 0, POSIX_FADV_SEQUENTIAL);
  52. 	}
  54. 	int err = 0;
  55. 	if(auto_fd_copy(fd, STDOUT_FILENO, bytes) < 0)
  56. 	{
  57. 		fprintf(stderr,
  58. 		        "%s: error: Failed copying data from '%s' to <stdout>: %s\n",
  59. 		        argv0,
  60. 		        filename,
  61. 		        strerror(errno));
  62. 		err = 1;
  63. 	}
  65. 	if(fd != STDIN_FILENO)
  66. 		if(close(fd) != 0)
  67. 		{
  68. 			fprintf(
  69. 			    stderr, "%s: error: Failed closing file '%s': %s\n", argv0, filename, strerror(errno));
  70. 			return 1;
  71. 		}
  73. 	return err;
  74. }
  76. static int
  77. copy_lines(const char *filename)
  78. {
  79. 	int err = 0;
  80. 	FILE *in = NULL;
  82. 	if(filename[0] == '-' && filename[1] == 0)
  83. 	{
  84. 		in = stdin;
  85. 	}
  86. 	else
  87. 	{
  88. 		in = fopen(filename, "r");
  89. 		if(in == NULL)
  90. 		{
  91. 			fprintf(
  92. 			    stderr, "%s: error: Failed opening file '%s': %s\n", argv0, filename, strerror(errno));
  93. 			return 1;
  94. 		}
  95. 		assert(in != stdin);
  96. 	}
  98. 	// Relative to EOF, GNU extension
  99. 	if(lines < 0)
  100. 	{
  101. 		struct strbuf
  102. 		{
  103. 			size_t len;
  104. 			size_t cap;
  105. 			char *buf;
  106. 		};
  107. 		size_t nlines = (size_t)-lines;
  108. 		size_t wini = 0;
  109. 		struct strbuf *win = calloc(nlines, sizeof(struct strbuf));
  110. 		if(!win)
  111. 		{
  112. 			fprintf(stderr, "%s: error: Failed allocating lines array: %s\n", argv0, strerror(errno));
  113. 			err = 1;
  114. 			goto copy_lines_end;
  115. 		}
  117. 		while(true)
  118. 		{
  119. 			ssize_t ret = getdelim(&buf, &buflen, delim, in);
  120. 			if(ret < 0)
  121. 			{
  122. 				if(errno == 0) break;
  124. 				fprintf(stderr,
  125. 				        "%s: error: Failed reading line from '%s': %s\n",
  126. 				        argv0,
  127. 				        filename,
  128. 				        strerror(errno));
  129. 				err = 1;
  130. 				break;
  131. 			}
  132. 			size_t nread = ret;
  134. 			if(win[wini].len)
  135. 			{
  136. 				if(write(STDOUT_FILENO, win[wini].buf, win[wini].len) < 0)
  137. 				{
  138. 					fprintf(stderr,
  139. 					        "%s: error: Failed writing line from '%s' to stdout: %s\n",
  140. 					        argv0,
  141. 					        filename,
  142. 					        strerror(errno));
  143. 					err = 1;
  144. 					break;
  145. 				}
  146. 			}
  148. 			if(nread == 0) continue;
  150. 			if(win[wini].cap < nread)
  151. 			{
  152. 				win[wini].buf = realloc(win[wini].buf, nread);
  153. 				if(!win[wini].buf)
  154. 				{
  155. 					fprintf(
  156. 					    stderr, "%s: error: Failed (re)allocating line buffer: %s\n", argv0, strerror(errno));
  157. 					err = 1;
  158. 					break;
  159. 				}
  160. 				win[wini].cap = nread;
  161. 			}
  163. 			win[wini].len = nread;
  164. 			memcpy(win[wini].buf, buf, nread);
  165. 			wini = (wini + 1) % nlines;
  166. 		}
  168. 		for(size_t i = 0; i < nlines; i++)
  169. 			free(win[i].buf);
  171. 		free(win);
  172. 	}
  173. 	else
  174. 	{
  175. 		size_t nlines = lines;
  176. 		for(size_t i = 0; i < nlines; i++)
  177. 		{
  178. 			ssize_t nread = getdelim(&buf, &buflen, delim, in);
  179. 			if(nread < 0)
  180. 			{
  181. 				if(errno == 0) break;
  183. 				fprintf(stderr,
  184. 				        "%s: error: Failed reading line from '%s': %s\n",
  185. 				        argv0,
  186. 				        filename,
  187. 				        strerror(errno));
  188. 				err = 1;
  189. 				break;
  190. 			}
  192. 			if(write(STDOUT_FILENO, buf, nread) < 0)
  193. 			{
  194. 				fprintf(stderr,
  195. 				        "%s: error: Failed writing line from '%s' to stdout: %s\n",
  196. 				        argv0,
  197. 				        filename,
  198. 				        strerror(errno));
  199. 				err = 1;
  200. 				break;
  201. 			}
  202. 		}
  203. 	}
  205. copy_lines_end:
  206. 	if(in != stdin)
  207. 		if(fclose(in) != 0)
  208. 		{
  209. 			fprintf(
  210. 			    stderr, "%s: error: Failed closing file '%s': %s\n", argv0, filename, strerror(errno));
  211. 			return 1;
  212. 		}
  214. 	return err;
  215. }
  217. static void
  218. usage(void)
  219. {
  220. 	fprintf(stderr, "Usage: head [-qvz] [-c size | -n num | -num] [file...]\n");
  221. }
  223. int
  224. main(int argc, char *argv[])
  225. {
  226. 	int (*copy_action)(const char *filename) = copy_lines;
  228. 	int print_header = 0;
  229. 	while(optind < argc)
  230. 	{
  231. 		/* Skip getopt(3) for parsing -num option due to how it works:
  232. 		 * - optstring = "12"; args="head -12" considered the same as -1 -2
  233. 		 * - optstring = "1:"; args="head -12" considered the same as -1 2
  234. 		 *
  235. 		 * And we need args="head -12" as "12"
  236. 		 */
  237. 		if(argv[optind] && argv[optind][0] == '-' && isdigit(argv[optind][1]))
  238. 		{
  239. 			char *arg = argv[optind] + 1;
  241. 			char *endptr = NULL;
  242. 			lines = strtol(arg, &endptr, 0);
  243. 			if(!(errno == 0 && endptr != NULL && *endptr == '\0'))
  244. 			{
  245. 				fprintf(stderr,
  246. 				        "%s: error: Failed parsing number for `-%s`: %s\n",
  247. 				        argv0,
  248. 				        arg,
  249. 				        strerror(errno));
  250. 				return 1;
  251. 			}
  253. 			optind++;
  254. 			continue;
  255. 		}
  257. 		int c = getopt_nolong(argc, argv, ":qvc:n:z");
  258. 		if(c == -1) break;
  260. 		switch(c)
  261. 		{
  262. 		case 'q':
  263. 			print_header = -1;
  264. 			break;
  265. 		case 'v':
  266. 			print_header = 1;
  267. 			break;
  268. 		case 'c':
  269. 		{
  270. 			char *endptr = NULL;
  271. 			unsigned long size = strtoul(optarg, &endptr, 0);
  272. 			if(errno != 0)
  273. 			{
  274. 				fprintf(stderr,
  275. 				        "%s: error: Failed parsing number for `-n %s`: %s\n",
  276. 				        argv0,
  277. 				        optarg,
  278. 				        strerror(errno));
  279. 				return 1;
  280. 			}
  282. 			if(endptr != NULL && *endptr != 0)
  283. 				if(apply_size_suffix(&size, endptr) != 0) return 1;
  285. 			bytes = size;
  286. 			copy_action = &copy_bytes;
  287. 			break;
  288. 		}
  289. 		case 'n':
  290. 		{
  291. 			char *endptr = NULL;
  292. 			lines = strtol(optarg, &endptr, 0);
  293. 			if(!(errno == 0 && endptr != NULL && *endptr == '\0'))
  294. 			{
  295. 				fprintf(stderr,
  296. 				        "%s: error: Failed parsing number for `-n %s`: %s\n",
  297. 				        argv0,
  298. 				        optarg,
  299. 				        strerror(errno));
  300. 				return 1;
  301. 			}
  302. 			break;
  303. 		}
  304. 		case 'z':
  305. 			delim = '\0';
  306. 			break;
  307. 		case ':':
  308. 			fprintf(stderr, "%s: error: Missing operand for option: '-%c'\n", argv0, optopt);
  309. 			usage();
  310. 			return 1;
  311. 		case '?':
  312. 			GETOPT_UNKNOWN_OPT
  313. 			usage();
  314. 			return 1;
  315. 		default:
  316. 			abort();
  317. 		}
  318. 	}
  320. 	argc -= optind;
  321. 	argv += optind;
  323. 	if(argc <= 0)
  324. 	{
  325. 		const char *filename = "-";
  327. 		if(print_header == 1)
  328. 		{
  329. 			printf(header_fmt, filename);
  330. 			fflush(stdout);
  331. 		}
  333. 		int err = copy_action(filename);
  335. 		free(buf);
  337. 		return err;
  338. 	}
  340. 	if(print_header == 0) print_header = argc > 1;
  342. 	int err = 0;
  344. 	for(int i = 0; i < argc; i++)
  345. 	{
  346. 		char *filename = argv[i];
  348. 		if(print_header > 0)
  349. 		{
  350. 			printf(header_fmt, filename);
  351. 			header_fmt = "\n==> %s <==\n";
  352. 			fflush(stdout);
  353. 		}
  355. 		if(copy_action(filename) != 0)
  356. 		{
  357. 			err = 1;
  358. 			break;
  359. 		}
  360. 	}
  362. 	free(buf);
  364. 	return err;
  365. }