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cmd-timer

run command at a specific interval git clone https://anongit.hacktivis.me/git/cmd-timer.git

timer.c (3053B)

    

  1. // SPDX-FileCopyrightText: 2025 Haelwenn (lanodan) Monnier <contact+cmd-timer@hacktivis.me>
  2. // SPDX-License-Identifier: MPL-2.0
  4. #define _POSIX_C_SOURCE 200809L
  5. #include "strtodur.h"
  7. #include <errno.h>
  8. #include <limits.h>   // UINT_MAX
  9. #include <signal.h>   // sigaction
  10. #include <spawn.h>    // posix_spawnp
  11. #include <stdio.h>    // fprintf, fputs
  12. #include <stdlib.h>   // exit
  13. #include <string.h>   // strerror
  14. #include <sys/wait.h> // waitpid
  15. #include <time.h>     // timer_create
  16. #include <unistd.h>   // sleep
  18. extern char **environ;
  19. static char **args;
  21. const char *argv0 = "timer";
  23. static void
  24. sig_timer(int sig)
  25. {
  26. 	pid_t child = -1;
  27. 	errno = 0;
  28. 	int ret = posix_spawnp(&child, args[0], NULL, NULL, args, environ);
  29. 	if(ret != 0)
  30. 	{
  31. 		fprintf(stderr, "timer: error: Failed spawning command '%s': %s\n", args[0], strerror(ret));
  32. 		exit(1);
  33. 	}
  34. }
  36. static void
  37. sig_chld(int sig)
  38. {
  39. 	int chld_stat = 0;
  40. 	waitpid((pid_t)-1, &chld_stat, WNOHANG);
  42. 	if(!WIFEXITED(chld_stat)) return;
  44. 	if(WEXITSTATUS(chld_stat) != 0) exit(WEXITSTATUS(chld_stat));
  45. }
  47. static void
  48. bad_usage()
  49. {
  50. 	fputs("Usage: timer <interval> <command> [arguments...]\n", stderr);
  51. 	exit(1);
  52. }
  54. int
  55. main(int argc, char *argv[])
  56. {
  57. 	argc--;
  58. 	argv++;
  60. 	if(argc < 2)
  61. 	{
  62. 		fprintf(stderr, "timer: error: Got '%d' arguments instead of at least 2\n", argc);
  63. 		bad_usage();
  64. 	}
  66. 	struct timespec dur = {
  67. 	    .tv_sec = 0,
  68. 	    .tv_nsec = 0,
  69. 	};
  71. 	if(strtodur(*argv, &dur) != 0) return 1;
  73. 	if(dur.tv_sec == 0 && dur.tv_nsec == 0)
  74. 	{
  75. 		fputs("timer: error: Got a duration of 0\n", stderr);
  76. 		return 1;
  77. 	}
  79. 	argc--;
  80. 	argv++;
  82. 	struct sigaction sa_alrm;
  83. 	sa_alrm.sa_handler = &sig_timer;
  84. 	sigemptyset(&sa_alrm.sa_mask);
  85. 	sa_alrm.sa_flags = SA_RESTART;
  87. 	if(sigaction(SIGALRM, &sa_alrm, NULL) != 0)
  88. 	{
  89. 		fprintf(stderr, "timer: error: Failed registering signal handler: %s\n", strerror(errno));
  90. 		return 1;
  91. 	}
  93. 	struct sigaction sa_chld;
  94. 	sa_chld.sa_handler = &sig_chld;
  95. 	sigemptyset(&sa_chld.sa_mask);
  96. 	sa_chld.sa_flags = SA_RESTART;
  98. 	if(sigaction(SIGCHLD, &sa_chld, NULL) != 0)
  99. 	{
  100. 		fprintf(stderr, "timer: error: Failed registering signal handler: %s\n", strerror(errno));
  101. 		return 1;
  102. 	}
  104. 	struct sigevent timer_se;
  105. 	timer_se.sigev_signo = SIGALRM;
  106. 	timer_se.sigev_notify = SIGEV_SIGNAL;
  108. 	timer_t timer;
  109. 	if(timer_create(0, &timer_se, &timer) != 0)
  110. 	{
  111. 		fprintf(stderr, "timer: error: Failed creating timer: %s\n", strerror(errno));
  112. 		return 1;
  113. 	}
  115. 	struct itimerspec timerspec = {
  116. 	    .it_value = dur,
  117. 	    .it_interval = dur,
  118. 	};
  120. 	if(timer_settime(timer, 0, &timerspec, NULL) != 0)
  121. 	{
  122. 		fprintf(stderr, "timer: error: Failed setting timer: %s\n", strerror(errno));
  123. 		return 1;
  124. 	}
  126. 	args = argv;
  128. 	sigset_t sigmask;
  129. 	sigfillset(&sigmask);
  130. 	if(sigdelset(&sigmask, SIGALRM) != 0)
  131. 	{
  132. 		fprintf(stderr, "timer: error: Failed adding SIGALARM to new sigmask: %s\n", strerror(errno));
  133. 		return 1;
  134. 	}
  135. 	if(sigdelset(&sigmask, SIGCHLD) != 0)
  136. 	{
  137. 		fprintf(stderr, "timer: error: Failed adding SIGCHLD to new sigmask: %s\n", strerror(errno));
  138. 		return 1;
  139. 	}
  141. 	while(sigsuspend(&sigmask))
  142. 		;
  144. 	return 0;
  145. }