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utils-std

Collection of commonly available Unix tools

nohup.c (2545B)

    

  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 <assert.h>
  8. #include <errno.h>
  9. #include <fcntl.h>  // open
  10. #include <limits.h> // PATH_MAX
  11. #include <signal.h>
  12. #include <stdbool.h>
  13. #include <stdio.h>    // fprintf
  14. #include <stdlib.h>   // getenv
  15. #include <string.h>   // strerror
  16. #include <sys/stat.h> // S_IRUSR, S_IWUSR
  17. #include <unistd.h>   // isatty
  19. static void
  20. usage()
  21. {
  22. 	fprintf(stderr, "Usage: nohup command [args ...]\n");
  23. }
  25. int
  26. main(int argc, char *argv[])
  27. {
  28. 	int nohup_fd = -1;
  30. 	if(argc <= 1)
  31. 	{
  32. 		usage();
  33. 		return 127;
  34. 	}
  36. 	if(signal(SIGHUP, SIG_IGN) == SIG_ERR)
  37. 	{
  38. 		fprintf(stderr, "nohup: Failed to set SIGHUP as ignored: %s\n", strerror(errno));
  39. 		return 127;
  40. 	}
  42. 	assert(errno == 0);
  43. 	if(isatty(1))
  44. 	{
  45. 		assert(errno == 0);
  46. 		nohup_fd = open("nohup.out", O_WRONLY | O_APPEND | O_CREAT, S_IRUSR | S_IWUSR);
  47. 		if(nohup_fd < 0)
  48. 		{
  49. 			fprintf(stderr,
  50. 			        "nohup: Warning: Failed opening ./nohup.out (%s), fallbacking to ~/nohup.out\n",
  51. 			        strerror(errno));
  53. 			char *home = getenv("HOME");
  54. 			if(!home)
  55. 			{
  56. 				fprintf(
  57. 				    stderr,
  58. 				    "nohup: $HOME is undefined, can't fallback writing from ./nohup.out to ~/nohup.out\n");
  59. 				return 127;
  60. 			}
  62. 			char home_nohup[PATH_MAX];
  63. 			if(snprintf(home_nohup, sizeof(home_nohup), "%s/nohup.out", home) < 0)
  64. 			{
  65. 				fprintf(
  66. 				    stderr, "nohup: Failed concatenating $HOME and '/nohup.out': %s\n", strerror(errno));
  67. 				return 127;
  68. 			}
  70. 			nohup_fd = open(home_nohup, O_WRONLY | O_APPEND | O_CREAT, S_IRUSR | S_IWUSR);
  71. 			if(nohup_fd < 0)
  72. 			{
  73. 				fprintf(stderr, "nohup: Error: Failed opening ~/nohup.out: %s\n", strerror(errno));
  74. 				return 127;
  75. 			}
  76. 		}
  78. 		if(dup2(nohup_fd, 1) < 0)
  79. 		{
  80. 			fprintf(
  81. 			    stderr, "nohup: Error: Failed assigning 'nohup.out' to stdout: %s\n", strerror(errno));
  82. 			return 127;
  83. 		}
  85. 		if(isatty(2))
  86. 		{
  87. 			assert(errno == 0);
  88. 			if(dup2(1, 2))
  89. 			{
  90. 				fprintf(stderr, "nohup: Error: Failed assigning stdout to stderr: %s\n", strerror(errno));
  91. 				return 127;
  92. 			}
  93. 		}
  94. 		else
  95. 			errno = 0; // isatty sets errno on returning false
  96. 	}
  97. 	else
  98. 		errno = 0; // isatty sets errno on returning false
  100. 	argc -= 1;
  101. 	argv += 1;
  102. 	(void)argc;
  104. 	assert(argv[0]);
  105. 	assert(errno == 0);
  106. 	if(execvp(argv[0], argv) < 0)
  107. 	{
  108. 		fprintf(stderr, "nohup: execvp(\"%s\", ...): %s\n", argv[0], strerror(errno));
  110. 		return (errno == ENOENT) ? 127 : 126;
  111. 	}
  113. 	assert(false);
  114. }