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utils-std

Collection of commonly available Unix tools

cat.c (2788B)

    

  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. #define _GNU_SOURCE // splice
  7. #include <assert.h>
  8. #include <errno.h>
  9. #include <fcntl.h>  // open, O_RDONLY, splice
  10. #include <stdint.h> // SIZE_MAX
  11. #include <stdio.h>  // fprintf, BUFSIZ
  12. #include <stdlib.h> // abort
  13. #include <string.h> // strerror, strncmp
  14. #include <unistd.h> // read, write, close, getopt
  16. static int
  17. concat(int fd, const char *fdname)
  18. {
  19. 	ssize_t c;
  20. 	char buf[BUFSIZ];
  22. 	assert(errno == 0);
  23. 	while((c = read(fd, buf, sizeof(buf))) > 0)
  24. 	{
  25. 		assert(errno == 0);
  26. 		if(write(1, buf, (size_t)c) < 0)
  27. 		{
  28. 			fprintf(stderr, "cat: Error writing: %s\n", strerror(errno));
  29. 			errno = 0;
  30. 			return 1;
  31. 		}
  32. 	}
  34. 	if(c < 0)
  35. 	{
  36. 		fprintf(stderr, "cat: Error reading ‘%s’: %s\n", fdname, strerror(errno));
  37. 		errno = 0;
  38. 		return 1;
  39. 	}
  41. 	return 0;
  42. }
  44. #ifdef HAS_SPLICE
  45. static int
  46. fd_copy(int fd, const char *fdname)
  47. {
  48. 	while(1)
  49. 	{
  50. 		assert(errno == 0);
  51. 		ssize_t ret =
  52. 		    splice(fd, NULL, 1, NULL, SIZE_MAX, SPLICE_F_MOVE | SPLICE_F_NONBLOCK | SPLICE_F_MORE);
  54. 		if(ret == 0) break;
  56. 		if(ret < 0)
  57. 		{
  58. 			switch(errno)
  59. 			{
  60. 			case EINVAL:
  61. 				errno = 0;
  62. 				return concat(fd, fdname);
  63. 			case EAGAIN:
  64. 				errno = 0;
  65. 				continue;
  66. 			default:
  67. 				fprintf(stderr, "cat: Error copying ‘%s’: %s\n", fdname, strerror(errno));
  68. 				errno = 0;
  69. 				return 1;
  70. 			}
  71. 		}
  72. 	}
  74. 	return 0;
  75. }
  76. #else // HAS_SPLICE
  77. #define fd_copy concat
  78. #endif // HAS_SPLICE
  80. static void
  81. usage()
  82. {
  83. 	fprintf(stderr, "Usage: cat [-u] [files ...]\n");
  84. }
  86. int
  87. main(int argc, char *argv[])
  88. {
  89. 	int c = -1;
  90. 	while((c = getopt(argc, argv, ":u")) != -1)
  91. 	{
  92. 		switch(c)
  93. 		{
  94. 		case 'u':
  95. 			// POSIX: Ignored, buffered streams aren't used
  96. 			break;
  97. 		case ':':
  98. 			fprintf(stderr, "cat: Error: Missing operand for option: '-%c'\n", optopt);
  99. 			usage();
  100. 			return 1;
  101. 		case '?':
  102. 			fprintf(stderr, "cat: Error: Unrecognised option: '-%c'\n", optopt);
  103. 			usage();
  104. 			return 1;
  105. 		default:
  106. 			abort();
  107. 		}
  108. 	}
  110. 	argc -= optind;
  111. 	argv += optind;
  113. 	if(argc < 1)
  114. 	{
  115. 		return fd_copy(0, "<stdin>");
  116. 	}
  118. 	for(int argi = 0; argi < argc; argi++)
  119. 	{
  120. 		if(strncmp(argv[argi], "-", 2) == 0)
  121. 		{
  122. 			if(fd_copy(0, "<stdin>") != 0)
  123. 			{
  124. 				return 1;
  125. 			}
  126. 		}
  127. 		else
  128. 		{
  129. 			assert(errno == 0);
  130. 			int fd = open(argv[argi], O_RDONLY);
  131. 			if(fd < 0)
  132. 			{
  133. 				fprintf(stderr, "cat: Error opening ‘%s’: %s\n", argv[argi], strerror(errno));
  134. 				errno = 0;
  135. 				return 1;
  136. 			}
  138. 			if(fd_copy(fd, argv[argi]) != 0)
  139. 			{
  140. 				return 1;
  141. 			}
  143. 			assert(errno == 0);
  144. 			if(close(fd) < 0)
  145. 			{
  146. 				fprintf(stderr, "cat: Error closing ‘%s’: %s\n", argv[argi], strerror(errno));
  147. 				errno = 0;
  148. 				return 1;
  149. 			}
  150. 		}
  151. 	}
  153. 	return 0;
  154. }