[helpers] Added an ability to become a daemon;

examples/helpers.c

@@ -37,6 +37,7 @@
 #include <stdint.h>
 #include <errno.h>
 #include <string.h>
+#include <fcntl.h>
 
 int openlistener_socket(int port)
 {
@@ -115,3 +116,55 @@ int normalize_path(char *path)
 
   return 0;
 }
+
+#define DM_MAX_CLOSE 8192
+
+int daemonize(void)
+{
+  pid_t pid;
+
+  /* fork */
+  pid = fork();
+  if (pid == -1) {
+    perror("fork() failed");
+    return EFAULT;
+  }
+  else if (pid != 0) {
+    exit(EXIT_SUCCESS);
+  }
+
+  /* create new session and progress group */
+  if (setsid() == -1) {
+    perror("setsid() failed");
+    return EFAULT;
+  }
+
+  /* set the working directory to the root directory */
+  if (chdir("/") == -1) {
+    perror("chdir() failed");
+    return EFAULT;
+  }
+
+  /* close all open files */
+  int fd;
+  int maxfd = sysconf(_SC_OPEN_MAX);
+  if (maxfd == -1)
+    maxfd = DM_MAX_CLOSE;   /* if this limit is indeterminate, take a guess */
+  for (fd = 0; fd < maxfd; fd++)
+    close(fd);
+
+  /* reopen standard fd's /dev/null */
+  close(STDIN_FILENO);
+  fd = open("/dev/null", O_RDWR);
+  if (fd != STDIN_FILENO) {           /* fd should be 0 */
+    return EBADFD;
+  }
+  if (dup2(STDIN_FILENO, STDOUT_FILENO) != STDOUT_FILENO) {
+    return EBADFD;
+  }
+  if (dup2(STDIN_FILENO, STDERR_FILENO) != STDERR_FILENO) {
+    return EBADFD;
+  }
+
+  return 0;
+}

examples/helpers.h

@@ -36,4 +36,6 @@ static inline void version_print(FILE *fso)
 }
 #endif
 
+int daemonize(void);
+
 #endif /* __SXMP_EXAMPLES_HELPERS_H__ */